Which Class 12 NCERT Biology lines has NEET asked about more than once?

68 of the 220 lines on this page were tested by two or more questions. The most tested: Population interactions (NCERT Class 12 Biology, Ch. 11, p. 197; 7 questions, 2021, 2022, 2023, 2025, 2026); Productivity, decomposition, energy flow (NCERT Class 12 Biology, Ch. 12, p. 207; 5 questions, 2020, 2023, 2024, 2025, 2026); Conservation (NCERT Class 12 Biology, Ch. 13, p. 224; 4 questions, 2022, 2024, 2025); Evil Quartet: four causes of biodiversity loss (NCERT Class 12 Biology, Ch. 13, p. 222; 4 questions, 2022, 2023, 2024, 2025); Immunity (NCERT Class 12 Biology, Ch. 7, p. 134; 4 questions, 2020, 2022, 2024, 2025).

How were these NCERT lines chosen?

Each line is an Class 12 NCERT Biology passage that a NEET question from 2020 to 2026 was matched to directly: the question can be answered from that line. 220 lines across 15 chapters, tied to 225 questions. The count covers the questions matched to our NCERT extract, which does not yet hold every page of the book, so a line missing here may still have been tested.

Which page numbers are these?

The page number printed in the NCERT book, not the page of a PDF file. Chapters are numbered as the current (2023 rationalised) edition prints them; a chapter that edition dropped is marked pre-2023 edition.

Which Class 12 NCERT Biology chapter has the most lines NEET tested?

Molecular Basis of Inheritance (Class 12, Chapter 5): 35 lines, tied to 40 questions.

NCERT line-by-line Biology Class 12 for NEET: the lines NEET tested

Reading NCERT line by line works best when you know which lines NEET turns into questions. This page lists 220 Class 12 NCERT Biology lines across 15 chapters that NEET questions from 2020 to 2026 were answered from, 225 questions in all. Each line gives the page printed in your NCERT book, the years and question numbers that tested it, and the lesson that teaches it.

Quotation marks mean NCERT's own words, checked against the book's page text and cut to a single line; open your copy at the page for the full passage. Where a line has no quotation, the text is our summary. A question is matched to a line only when the line alone answers it, and only questions you can solve on this site are listed.

Each chapter opens with its topic index: the PrepBrix lessons on that chapter in NCERT page order, each with the first printed page it cites and its count of past NEET questions. The Class 11 lines are on their own page.

Class 12, Chapter 1: Sexual Reproduction in Flowering Plants

Printed pages 1–25. 20 lines tested by 19 questions.

Topics in this chapter (4), in NCERT order

Flower Structure Gametogenesisp. 65 PYQs
Pollination Fertilizationp. 1211 PYQs
Post Fertilization Seed Fruitp. 185 PYQs
Apomixis Polyembryonyp. 230 PYQs

Angiosperm anther: bilobed, two theca per lobe (dithecous)
“A typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous”
NCERT Class 12 Biology, Ch. 1, p. 5, section 1.7
Tested in: NEET 2026 Q151
Learn it: Flower Structure Gametogenesis
Tapetum nourishes pollen; its cells often have more than one nucleus
“The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus”
NCERT Class 12 Biology, Ch. 1, p. 5, section 1.7
Tested in: NEET 2025 Q100
Learn it: Flower Structure Gametogenesis
Pollen grain is the male gametophyte
“Pollen grain: The pollen grains represent the male gametophytes. If you touch the opened anthers of Hibiscus or any other flower you would find deposition of yellowish powdery pollen grains on your fingers”
NCERT Class 12 Biology, Ch. 1, p. 6, section 1.2.1
Tested in: NEET 2020 Q92
Learn it: Flower Structure Gametogenesis
Pollen viability duration varies by species
“In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release”
NCERT Class 12 Biology, Ch. 1, p. 8, section 1.2.1
Tested in: NEET 2021 Q145
Learn it: Pollination Fertilization
Embryo sac is the female gametophyte in nucellus
“Located in the nucellus is the embryo sac or female gametophyte”
NCERT Class 12 Biology, Ch. 1, p. 9, section 1.2.2
Tested in: NEET 2020 Q92
Learn it: Flower Structure Gametogenesis
MMC: one meiosis then three mitoses form embryo sac
“The MMC undergoes meiotic division. What is the importance of the MMC undergoing meiosis? Meiosis results in the production of four megaspores”
NCERT Class 12 Biology, Ch. 1, p. 10, section 1.2.2
Tested in: NEET 2025 Q97
Learn it: Flower Structure Gametogenesis · Pollination Fertilization
Egg apparatus vs polar nuclei in embryo sac
Tested 2 times
“Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell”
NCERT Class 12 Biology, Ch. 1, p. 11, section 1.2.2
Tested in: NEET 2026 Q154, NEET 2025 Q139
Learn it: Flower Structure Gametogenesis · Pollination Fertilization
Filiform apparatus of synergids guides the pollen tube
“The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid”
NCERT Class 12 Biology, Ch. 1, p. 11, section 1.2.2
Tested in: NEET 2026 Q154
Learn it: Pollination Fertilization
Xenogamy: pollen to a different plant's stigma
“Xenogamy – Transfer of pollen grains from anther to the stigma of a different plant”
NCERT Class 12 Biology, Ch. 1, p. 12, section 1.2.3
Tested in: NEET 2021 Q113
Learn it: Pollination Fertilization
Cleistogamous flowers are invariably autogamous
“Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma”
NCERT Class 12 Biology, Ch. 1, p. 12, section 1.2.3
Tested in: NEET 2022 Q121
Learn it: Pollination Fertilization
Wind/water pollination produces enormous pollen
“To compensate for this uncertainties and associated loss of pollen grains, the flowers produce enormous amount of pollen when compared to the number of ovules available for pollination”
NCERT Class 12 Biology, Ch. 1, p. 12, section 1.2.3
Tested in: NEET 2025 Q142
Learn it: Pollination Fertilization
Pollination & double fertilization
In short: Pollination: self (autogamy, geitonogamy) vs cross (xenogamy)
NCERT Class 12 Biology, Ch. 1, p. 12, section 1.5
Tested in: NEET 2023 Q131
Learn it: Pollination Fertilization
Corn cob stigma-style waves in wind to trap pollen
“…a familiar example is the corn cob – the ears you see are nothing but the stigma and style which wave in the wind to trap pollen grains”
NCERT Class 12 Biology, Ch. 1, p. 13, section 1.2.3
Tested in: NEET 2023 Q130
Learn it: Pollination Fertilization
Water pollination: waterlily, mucilage, ribbon pollen
“In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind”
NCERT Class 12 Biology, Ch. 1, p. 13, section 1.2.3
Tested in: NEET 2024 Q111
Learn it: Pollination Fertilization
Wind and water pollinated flowers lack colour and nectar
Tested 3 times
“Both wind and water pollinated flowers are not very colourful and do not produce nectar”
NCERT Class 12 Biology, Ch. 1, p. 13, section 1.2.3
Tested in: NEET 2025 Q142, NEET 2024 Q111, NEET 2022 Q117
Learn it: Pollination Fertilization
Wind-pollinated flowers have well-exposed stamens
“They often possess well-exposed stamens (so that the pollens are easily dispersed into wind currents, Figure 1.10) and large often-feathery stigma to easily trap air-borne pollen grains”
NCERT Class 12 Biology, Ch. 1, p. 13, section 1.2.3
Tested in: NEET 2024 Q140
Learn it: Pollination Fertilization
Insect-pollinated flowers are large, colourful, nectar-rich
Tested 2 times
“Majority of insect-pollinated flowers are large, colourful, fragrant and rich in nectar”
NCERT Class 12 Biology, Ch. 1, p. 14, section 1.2.3
Tested in: NEET 2023 Q122, NEET 2022 Q117
Learn it: Pollination Fertilization
Double fertilisation: diploid zygote, triploid primary endosperm nucleus
Tested 2 times
“One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy. This results in the formation of a diploid cell, the zygote”
NCERT Class 12 Biology, Ch. 1, p. 18, section 1.6
Tested in: NEET 2026 Q156, NEET 2023 Q131
Learn it: Pollination Fertilization · Post Fertilization Seed Fruit
False fruit forms when thalamus contributes
“…in a few species such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits”
NCERT Class 12 Biology, Ch. 1, p. 20, section 1.4.3
Tested in: NEET 2022 Q136
Learn it: Post Fertilization Seed Fruit
Non-albuminous seeds and perisperm defined
“Non‐albuminous seeds have no residual endosperm as it is completely consumed during embryo development (e.g., pea, groundnut)”
NCERT Class 12 Biology, Ch. 1, p. 20, section 1.4.3
Tested in: NEET 2026 Q155
Learn it: Post Fertilization Seed Fruit

Class 12, Chapter 2: Human Reproduction

Printed pages 26–40. 22 lines tested by 18 questions.

Topics in this chapter (4), in NCERT order

Vas deferens: seminal vesicle duct, ejaculatory duct
“It receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct”
NCERT Class 12 Biology, Ch. 2, p. 27, section 2.1
Tested in: NEET 2023 Q171
Learn it: Male Reproductive System
Male sex accessory ducts: rete testis, vasa efferentia, epididymis, vas deferens
“The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens”
NCERT Class 12 Biology, Ch. 2, p. 27, section 2.1
Tested in: NEET 2026 Q143
Learn it: Male Reproductive System
Female reproductive system
In short: Ovaries — oogonia → primary oocyte (arrested in prophase I) → secondary oocyte at puberty (haploid, arrested in metaphase II)
NCERT Class 12 Biology, Ch. 2, p. 28, section 2.2
Tested in: NEET 2022 Q160
Learn it: Female Reproductive System
Fallopian tube regions: infundibulum, ampulla, isthmus
Tested 2 times
“…the part closer to the ovary is the funnel-shaped infundibulum”
NCERT Class 12 Biology, Ch. 2, p. 29, section 2.2
Tested in: NEET 2026 Q143, NEET 2024 Q154
Learn it: Female Reproductive System · Male Reproductive System
Hymen not a reliable indicator of virginity
“The hymen is often torn during the first coitus (intercourse). However, it can also be broken by a sudden fall or jolt, insertion of a vaginal tampon, active participation in some sports like horseback riding, cycling”
NCERT Class 12 Biology, Ch. 2, p. 30, section 2.2
Tested in: NEET 2024 Q185
Learn it: Female Reproductive System
Cervical canal with vagina forms birth canal
“The uterus opens into vagina through a narrow cervix. The cavity of the cervix is called cervical canal”
NCERT Class 12 Biology, Ch. 2, p. 30, section 2.2
Tested in: NEET 2023 Q171
Learn it: Male Reproductive System
Spermiogenesis and spermiation defined
“The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis”
NCERT Class 12 Biology, Ch. 2, p. 31, section 2.3
Tested in: NEET 2022 Q171
Learn it: Male Reproductive System
LH-Leydig-androgens; FSH-Sertoli-spermiogenesis
“LH acts at the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis”
NCERT Class 12 Biology, Ch. 2, p. 31, section 2.3
Tested in: NEET 2024 Q164
Learn it: Male Reproductive System
Oogenesis begins in embryo; spermatogenesis at puberty
“…produce sperms by spermatogenesis that begins at puberty”
NCERT Class 12 Biology, Ch. 2, p. 32, section 2.3
Tested in: NEET 2022 Q163
Learn it: Male Reproductive System · Female Reproductive System
Sperm structure: nucleus, acrosome, mitochondria, tail
“The sperm head contains an elongated haploid nucleus, the anterior portion of which is covered by a cap-like structure, acrosome”
NCERT Class 12 Biology, Ch. 2, p. 32, section 2.3
Tested in: NEET 2025 Q150
Learn it: Male Reproductive System
Oogenesis starts in the embryo; no oogonia added after birth
“Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary; no more oogonia are formed and added after birth”
NCERT Class 12 Biology, Ch. 2, p. 32, section 2.3
Tested in: NEET 2022 Q160
Learn it: Female Reproductive System
Menarche; missed menstruation may indicate pregnancy
“The first menstruation begins at puberty and is called menarche”
NCERT Class 12 Biology, Ch. 2, p. 33, section 2.4
Tested in: NEET 2025 Q92
Learn it: Menstrual Cycle
Graafian follicle ruptures to release the secondary oocyte (ovulation)
“The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation”
NCERT Class 12 Biology, Ch. 2, p. 33, section 2.4
Tested in: NEET 2020 Q111
Learn it: Female Reproductive System
Secondary oocyte forms the zona pellucida around it
“The secondary oocyte forms a new membrane called zona pellucida surrounding it”
NCERT Class 12 Biology, Ch. 2, p. 33, section 2.4
Tested in: NEET 2026 Q173
Learn it: Fertilization Pregnancy
Cyclic menstruation spans menarche to menopause
“…menstrual cycles ceases around 50 years of age; that is termed as menopause. Cyclic menstruation is an indicator of normal reproductive phase and extends between menarche and menopause”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.4
Tested in: NEET 2025 Q92
Learn it: Menstrual Cycle
LH and FSH stimulate follicles to secrete estrogen
“…gonadotropins (LH and FSH) increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.4
Tested in: NEET 2024 Q164
Learn it: Male Reproductive System
Endometrium needed for implantation; corpus luteum degeneration
“Such an endometrium is necessary for implantation of the fertilised ovum and other events of pregnancy”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.4
Tested in: NEET 2023 Q181
Learn it: Fertilization Pregnancy
LH and FSH stimulate follicular development
“…gonadotropins (LH and FSH) increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.4
Tested in: NEET 2022 Q163
Learn it: Male Reproductive System
LH surge causes ovulation; corpus luteum secretes progesterone
Tested 2 times
“Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.4
Tested in: NEET 2026 Q145, NEET 2025 Q115
Learn it: Female Reproductive System · Menstrual Cycle
Fertilisation: zona pellucida contact completes oocyte meiosis
Tested 3 times
“During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum”
NCERT Class 12 Biology, Ch. 2, p. 35, section 2.5
Tested in: NEET 2026 Q173, NEET 2021 Q163, NEET 2020 Q111
Learn it: Fertilization Pregnancy · Female Reproductive System
Relaxin secreted by ovary in late pregnancy
Tested 2 times
“In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary”
NCERT Class 12 Biology, Ch. 2, p. 37, section 2.6
Tested in: NEET 2026 Q166, NEET 2025 Q115
Learn it: Female Reproductive System · Fertilization Pregnancy
Embryonic development timeline: heart, limbs, organs, hair
“In human beings, after one month of pregnancy, the embryo's heart is formed”
NCERT Class 12 Biology, Ch. 2, p. 38, section 2.6
Tested in: NEET 2025 Q157
Learn it: Fertilization Pregnancy

Class 12, Chapter 3: Reproductive Health

Printed pages 41–50. 15 lines tested by 12 questions.

Topics in this chapter (3), in NCERT order

Statutory ban on amniocentesis for sex-determination
“Statutory ban on amniocentesis for sex-determination to legally check increasing menace of female foeticides, massive child immunisation, etc., are some programmes that merit mention in this connection”
NCERT Class 12 Biology, Ch. 3, p. 42, section 3.5
Tested in: NEET 2023 Q174
Learn it: Amniocentesis Art
Contraception methods
In short: Natural (rhythm, withdrawal, lactational amenorrhoea), barrier (condoms, diaphragm, IUDs — Cu releasing, hormonal — Mirena), oral (Mala-D, Saheli — non-steroidal), implants/injections, surgical (vasectomy, tubectomy)
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2024 Q172
Learn it: Birth Control Methods
IUD types: non-medicated, copper, hormone releasing
Tested 3 times
“These Intra Uterine Devices are presently available as the non-medicated IUDs (e.g., Lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and the hormone releasing IUDs (Progestasert, LNG-20)”
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2024 Q179, NEET 2022 Q159, NEET 2021 Q181
Learn it: Birth Control Methods
Barrier methods block cervix (diaphragm, caps, vaults)
Tested 3 times
“In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers”
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2023 Q162, NEET 2022 Q198, NEET 2021 Q174
Learn it: Birth Control Methods
IUDs increase phagocytosis of sperms in uterus
Tested 2 times
“IUDs increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms”
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2022 Q198, NEET 2021 Q174
Learn it: Birth Control Methods
Lactational amenorrhea prevents ovulation after parturition
“Lactational amenorrhea (absence of menstruation) method is based on the fact that ovulation”
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2022 Q198
Learn it: Birth Control Methods
Withdrawal/coitus interruptus is a natural method
“Natural methods work on the principle of avoiding chances of ovum and sperms meeting”
NCERT Class 12 Biology, Ch. 3, p. 44, section 3.3
Tested in: NEET 2023 Q162
Learn it: Birth Control Methods
Implants deliver progestogens under the skin
“Progestogens alone or in combination with estrogen can also be used by females as injections or implants under the skin”
NCERT Class 12 Biology, Ch. 3, p. 45, section 3.3
Tested in: NEET 2024 Q179
Learn it: Birth Control Methods
Contraceptive pills inhibit ovulation and implantation
“They inhibit ovulation and implantation as well as”
NCERT Class 12 Biology, Ch. 3, p. 45, section 3.3
Tested in: NEET 2022 Q198
Learn it: Birth Control Methods
Surgical sterilisation: vasectomy (male), tubectomy (female)
“Surgical methods, also called sterilisation, are generally advised for the male/female partner as a terminal method to prevent any more”
NCERT Class 12 Biology, Ch. 3, p. 45, section 3.3
Tested in: NEET 2023 Q162
Learn it: Birth Control Methods
Saheli is an oral non-steroidal contraceptive
“Saheli–the new oral contraceptive for the females contains a non-steroidal preparation. It is a ‘once a week’ pill with very few side effects and high contraceptive value”
NCERT Class 12 Biology, Ch. 3, p. 45, section 3.3
Tested in: NEET 2023 Q162
Learn it: Birth Control Methods
Vasectomy removes vas deferens; tubectomy removes fallopian tube
“In vasectomy, a small part of the vas deferens is removed or tied up through a small incision on the scrotum”
NCERT Class 12 Biology, Ch. 3, p. 46, section 3.3
Tested in: NEET 2021 Q174
Learn it: Birth Control Methods
STDs & infertility
In short: STDs: gonorrhoea, syphilis, chlamydia, trichomoniasis, genital herpes, HPV (genital warts), HIV/AIDS
NCERT Class 12 Biology, Ch. 3, p. 47, section 3.4
Tested in: NEET 2020 Q99
Learn it: Reproductive Health STDs
Gonorrhoea is a curable STI
Tested 2 times
“Gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and of course, the most discussed infection in the recent years, HIV leading to AIDS are some of the common STIs”
NCERT Class 12 Biology, Ch. 3, p. 47, section 3.4
Tested in: NEET 2026 Q139, NEET 2023 Q164
Learn it: Reproductive Health STDs
Amniocentesis & ART
Tested 2 times
In short: Amniocentesis: foetal-cell analysis from amniotic fluid for chromosomal abnormalities
NCERT Class 12 Biology, Ch. 3, p. 48, section 3.5
Tested in: NEET 2026 Q142, NEET 2023 Q174
Learn it: Amniocentesis Art

Class 12, Chapter 4: Principles of Inheritance and Variation

Printed pages 51–78. 18 lines tested by 23 questions.

Topics in this chapter (6), in NCERT order

Mendel Inheritancep. 598 PYQs
Incomplete Dominance Codominancep. 606 PYQs
Linkage Recombination Mappingp. 673 PYQs
Sex Determination Linkagep. 712 PYQs
Mendelian Disorders Pedigreep. 724 PYQs
Mutations Genetic Disordersp. 735 PYQs

Mendel's 14 varieties, 7 characters
Tested 3 times
“Mendel selected 14 true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits”
NCERT Class 12 Biology, Ch. 4, p. 54, section 4.1
Tested in: NEET 2026 Q175, NEET 2022 Q135, NEET 2020 Q130
Learn it: Mendel Inheritance
Punnett square diagram
“The production of gametes by the parents, the formation of the zygotes, the F1 and F2 plants can be understood from a diagram called Punnett Square”
NCERT Class 12 Biology, Ch. 4, p. 57, section 4.2
Tested in: NEET 2021 Q109
Learn it: Mendel Inheritance
Mendel's laws
Tested 3 times
In short: Law of dominance, segregation (purity of gametes), independent assortment
NCERT Class 12 Biology, Ch. 4, p. 59, section 4.1
Tested in: NEET 2025 Q94, NEET 2024 Q133, NEET 2021 Q184
Learn it: Mendel Inheritance · Mendelian Disorders Pedigree
Law of Dominance statements
Tested 2 times
“Characters are controlled by discrete units called factors. (ii) Factors occur in pairs. (iii) In a dissimilar pair of factors one member of the pair dominates (dominant) the other (recessive)”
NCERT Class 12 Biology, Ch. 4, p. 59, section 4.2.1
Tested in: NEET 2026 Q175, NEET 2024 Q123
Learn it: Mendel Inheritance
Inheritance patterns
In short: Incomplete dominance: snapdragon RR (red), Rr (pink), rr (white)
NCERT Class 12 Biology, Ch. 4, p. 60, section 4.2
Tested in: NEET 2024 Q131
Learn it: Incomplete Dominance Codominance
ABO alleles: i produces no sugar
Tested 3 times
“The alleles I A and I B produce a slightly different form of the sugar while allele i does not produce any sugar”
NCERT Class 12 Biology, Ch. 4, p. 61, section 4.2.2.2
Tested in: NEET 2026 Q169, NEET 2024 Q197, NEET 2020 Q121
Learn it: Incomplete Dominance Codominance
Sturtevant maps genes via recombination frequency
“His student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and 'mapped' their position on the chromosome”
NCERT Class 12 Biology, Ch. 4, p. 67, section 4.3.3
Tested in: NEET 2023 Q126
Learn it: Linkage Recombination Mapping
Linkage & crossing over
Tested 2 times
In short: Linkage: genes on same chromosome inherited together
NCERT Class 12 Biology, Ch. 4, p. 67, section 4.4
Tested in: NEET 2022 Q150, NEET 2022 Q188
Learn it: Linkage Recombination Mapping
9:3:3:1 is the F2 ratio expected when two genes are independent
“He observed that the two genes did not segregate independently of each other and the F2 ratio deviated very significantly from the 9:3:3:1 ratio (expected when the two genes are independent”
NCERT Class 12 Biology, Ch. 4, p. 67, section 4.4
Tested in: NEET 2025 Q94
Learn it: Mendel Inheritance
Pleiotropy: one gene, multiple phenotypic expression
“There are however instances where a single gene can exhibit multiple phenotypic expression. Such a gene is called a pleiotropic gene”
NCERT Class 12 Biology, Ch. 4, p. 69, section 4.4
Tested in: NEET 2023 Q101
Learn it: Incomplete Dominance Codominance
XO sex determination in grasshopper
“…in a large number of insects the mechanism of sex determination is of the XO type, i.e., all eggs bear an additional X-chromosome besides the other chromosomes”
NCERT Class 12 Biology, Ch. 4, p. 70, section 4.6
Tested in: NEET 2022 Q126
Learn it: Sex Determination Linkage
Genetic disorders
Tested 2 times
In short: Mendelian: sickle cell anaemia (autosomal recessive), thalassaemia, phenylketonuria, haemophilia (X-linked recessive)
NCERT Class 12 Biology, Ch. 4, p. 73, section 4.7
Tested in: NEET 2026 Q138, NEET 2021 Q184
Learn it: Mutations Genetic Disorders · Mendelian Disorders Pedigree
Colour Blindness
In short: Colour blindness is a sex-linked recessive disorder due to a defect in either the red or green cone of the eye, resulting in failure to discriminate between red and green colour, caused by mutation in genes present on the X chromosome
NCERT Class 12 Biology, Ch. 4, p. 73, section 4.8.2
Tested in: NEET 2022 Q191
Learn it: Mendelian Disorders Pedigree
Pedigree examples: dominant vs recessive trait
“A representative pedigree is shown in Figure 4.14 for dominant and recessive traits”
NCERT Class 12 Biology, Ch. 4, p. 73, section 4.8.2
Tested in: NEET 2022 Q142
Learn it: Mendelian Disorders Pedigree
Colour Blindness (continued)
In short: The son of a woman who carries the gene has a 50 per cent chance of being colour blind
NCERT Class 12 Biology, Ch. 4, p. 74, section 4.8.2
Tested in: NEET 2022 Q191
Learn it: Mendelian Disorders Pedigree
Chromosome locations: Klinefelter, Thalassemia genes
“…caused due to the presence of an additional copy of X-chromosome resulting into a karyotype of 47, XXY”
NCERT Class 12 Biology, Ch. 4, p. 75, section 4.8.2/4.8.3
Tested in: NEET 2024 Q163
Learn it: Mutations Genetic Disorders
Down's syndrome: trisomy 21, palm crease
Tested 3 times
“…the presence of an additional copy of the chromosome number 21 (trisomy of 21)”
NCERT Class 12 Biology, Ch. 4, p. 76, section 4.8.3
Tested in: NEET 2026 Q138, NEET 2024 Q163, NEET 2023 Q155
Learn it: Mutations Genetic Disorders
Klinefelter's syndrome: 47, XXY; masculine with gynaecomastia; sterile
“This genetic disorder is also caused due to the presence of an additional copy of”
NCERT Class 12 Biology, Ch. 4, p. 76, section 4.8.3
Tested in: NEET 2023 Q148
Learn it: Mutations Genetic Disorders

Class 12, Chapter 5: Molecular Basis of Inheritance

Printed pages 79–109. 35 lines tested by 40 questions.

Topics in this chapter (7), in NCERT order

DNA RNA Structurep. 811 PYQ
Genetic Material DNA Packagingp. 839 PYQs
DNA Replicationp. 894 PYQs
Genetic Codep. 951 PYQ
Transcription Translationp. 9515 PYQs
Gene Regulation Lac Operonp. 1004 PYQs
Human Genome Projectp. 1024 PYQs

DNA structure
Tested 2 times
In short: Watson-Crick double helix: antiparallel strands
NCERT Class 12 Biology, Ch. 5, p. 81, section 5.1
Tested in: NEET 2023 Q198, NEET 2021 Q176
Learn it: DNA RNA Structure · Transcription Translation
Packaging of DNA Helix
Tested 3 times
In short: The distance between two consecutive base pairs in DNA is 0.34 nm
NCERT Class 12 Biology, Ch. 5, p. 83, section 5.1.2
Tested in: NEET 2023 Q151, NEET 2022 Q185, NEET 2020 Q106
Learn it: Genetic Material DNA Packaging
Packaging of DNA Helix
Tested 3 times
In short: In eukaryotes, positively charged basic proteins called histones, rich in the basic amino acid residues lysine and arginine, organise into a unit of eight molecules called a histone octamer
NCERT Class 12 Biology, Ch. 5, p. 83, section 5.1.2
Tested in: NEET 2025 Q111, NEET 2023 Q151, NEET 2022 Q115
Learn it: Genetic Material DNA Packaging
Packaging of DNA Helix
Tested 2 times
In short: The beads-on-string chromatin is packaged into chromatin fibers, further coiled and condensed at the metaphase stage of cell division to form chromosomes
NCERT Class 12 Biology, Ch. 5, p. 84, section 5.1.2
Tested in: NEET 2025 Q168, NEET 2022 Q115
Learn it: Genetic Material DNA Packaging
Transforming Principle (Griffith)
Tested 2 times
In short: In 1928, Frederick Griffith worked with Streptococcus pneumoniae, which forms smooth (S, mucous/polysaccharide coat, virulent) or rough (R, no coat, non-virulent) colonies
NCERT Class 12 Biology, Ch. 5, p. 84, section 5.2
Tested in: NEET 2025 Q168, NEET 2024 Q148
Learn it: Genetic Material DNA Packaging
The Genetic Material is DNA (Hershey-Chase)
Tested 2 times
In short: Alfred Hershey and Martha Chase (1952) worked with bacteriophages
NCERT Class 12 Biology, Ch. 5, p. 85, section 5.2.1
Tested in: NEET 2025 Q168, NEET 2023 Q134
Learn it: Genetic Material DNA Packaging
RNA mutates faster than DNA
“Both DNA and RNA are able to mutate. In fact, RNA being unstable, mutate at a faster rate”
NCERT Class 12 Biology, Ch. 5, p. 87, section 5.2.2
Tested in: NEET 2023 Q156
Learn it: Viruses Viroids Lichens
RNA World
In short: RNA was the first genetic material
NCERT Class 12 Biology, Ch. 5, p. 88, section 5.3
Tested in: NEET 2025 Q159
Learn it: Genetic Material DNA Packaging
DNA replication
In short: Semi-conservative (Meselson-Stahl 1958, ¹⁵N → ¹⁴N density gradient)
NCERT Class 12 Biology, Ch. 5, p. 89, section 5.4
Tested in: NEET 2024 Q148
Learn it: Genetic Material DNA Packaging · DNA Replication
E. coli divides every 20 minutes
“…after 20 minutes; E. coli divides in 20 minutes] had a hybrid or intermediate density”
NCERT Class 12 Biology, Ch. 5, p. 89, section 5.4.1
Tested in: NEET 2022 Q193
Learn it: DNA Replication
DNA polymerase synthesises only 5' to 3'
“…catalyse polymerisation only in one direction, that is 5'à3'”
NCERT Class 12 Biology, Ch. 5, p. 90, section 5.4.2
Tested in: NEET 2024 Q139
Learn it: DNA Replication
DNA ligase joins discontinuous fragments
“The discontinuously synthesised fragments are later joined by the enzyme DNA ligase”
NCERT Class 12 Biology, Ch. 5, p. 90, section 5.4.2
Tested in: NEET 2020 Q133
Learn it: rDNA Tools Restriction Ligase
DNA-dependent DNA polymerase uses a DNA template
“The main enzyme is referred to as DNA-dependent DNA polymerase, since it uses a DNA template to catalyse the polymerisation of deoxynucleotides”
NCERT Class 12 Biology, Ch. 5, p. 90, section 5.4.2
Tested in: NEET 2026 Q167
Learn it: Transcription Translation
Eukaryotic DNA replication occurs in S phase
“In eukaryotes, the replication of DNA takes place at S-phase of the cell-cycle”
NCERT Class 12 Biology, Ch. 5, p. 91, section 5.4.2
Tested in: NEET 2023 Q118
Learn it: DNA Replication
Transcription complementarity uses uracil
“Here also, the principle of complementarity governs the process of transcription, except the adenosine complements now forms base pair with uracil instead of thymine”
NCERT Class 12 Biology, Ch. 5, p. 91, section 5.5
Tested in: NEET 2023 Q198
Learn it: Transcription Translation
Transcription unit: promoter, gene, terminator
“A transcription unit in DNA is defined primarily by the three regions in the DNA: (i) A Promoter (ii) The Structural gene (iii) A Terminator”
NCERT Class 12 Biology, Ch. 5, p. 91, section 5.5.1
Tested in: NEET 2024 Q132
Learn it: Transcription Translation
Template strand (3'→5') is copied; RNA has the coding strand sequence with U for T
“…the strand that has the polarity 3'→5' acts as a template, and is also referred to as template strand”
NCERT Class 12 Biology, Ch. 5, p. 92, section 5.4.2
Tested in: NEET 2024 Q169
Learn it: Transcription Translation
Three RNAs needed for protein synthesis
Tested 2 times
“In bacteria, there are three major types of RNAs: mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA)”
NCERT Class 12 Biology, Ch. 5, p. 93, section 5.5.3
Tested in: NEET 2025 Q160, NEET 2021 Q183
Learn it: Transcription Translation
A single DNA-dependent RNA polymerase transcribes all RNA in bacteria
“There is single DNA-dependent RNA polymerase that catalyses transcription of all types of RNA in bacteria”
NCERT Class 12 Biology, Ch. 5, p. 93, section 5.5.3
Tested in: NEET 2024 Q139
Learn it: DNA Replication
RNA polymerase opens DNA helix
“It somehow also facilitates opening of the helix and continues elongation”
NCERT Class 12 Biology, Ch. 5, p. 94, section 5.5.3
Tested in: NEET 2020 Q116
Learn it: Transcription Translation
Sigma initiates, rho terminates transcription
Tested 2 times
“The RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation-factor (σ) and termination-factor (ρ) to initiate and terminate the transcription, respectively”
NCERT Class 12 Biology, Ch. 5, p. 94, section 5.5.3
Tested in: NEET 2025 Q119, NEET 2021 Q146
Learn it: Transcription Translation
Transcription & translation
Tested 3 times
In short: Transcription: DNA → mRNA via RNA polymerase
NCERT Class 12 Biology, Ch. 5, p. 95, section 5.5
Tested in: NEET 2026 Q167, NEET 2023 Q107, NEET 2021 Q136
Learn it: Transcription Translation
Processed hnRNA becomes mRNA, then exported
“…hnRNA undergoes additional processing called as capping and tailing”
NCERT Class 12 Biology, Ch. 5, p. 95, section 5.5.3
Tested in: NEET 2025 Q166
Learn it: Transcription Translation
Genetic Code
Tested 2 times
In short: George Gamow, a physicist, argued that since there are only 4 bases and they must code for 20 amino acids, the code should be a combination of bases, and proposed that the code is made of three nucleotides (a triplet), since a permutation of 4^3 (4x4x4) generates 64 codons, more than the 20 required
NCERT Class 12 Biology, Ch. 5, p. 95, section 5.6
Tested in: NEET 2025 Q107, NEET 2024 Q148
Learn it: Genetic Code · Genetic Material DNA Packaging
Aminoacylation is first phase of translation
“…in the first phase itself amino acids are activated in the presence of ATP and linked to their cognate tRNA– a process commonly called as charging of tRNA or aminoacylation of tRNA to be more specific”
NCERT Class 12 Biology, Ch. 5, p. 98, section 5.7
Tested in: NEET 2020 Q123
Learn it: Transcription Translation
Translation begins at small subunit-mRNA encounter
“When the small subunit encounters an mRNA, the process of translation of the mRNA to protein begins”
NCERT Class 12 Biology, Ch. 5, p. 99, section 5.7
Tested in: NEET 2022 Q132
Learn it: Transcription Translation
Lac operon
In short: Jacob-Monod model
NCERT Class 12 Biology, Ch. 5, p. 100, section 5.7
Tested in: NEET 2023 Q168
Learn it: Gene Regulation Lac Operon
Lac operon elucidated by Francois Jacob and Jacque Monod
“The elucidation of the lac operon was also a result of a close association between a geneticist, Francois Jacob and a biochemist, Jacque Monod”
NCERT Class 12 Biology, Ch. 5, p. 100, section 5.7
Tested in: NEET 2025 Q107
Learn it: Genetic Code
Permease transports lactose into cell
“…the lactose is transported into the cells through the action of permease”
NCERT Class 12 Biology, Ch. 5, p. 101, section 5.8
Tested in: NEET 2024 Q112
Learn it: Gene Regulation Lac Operon
lac repressor is made constitutively from the i gene; an inducer inactivates it
Tested 2 times
“The repressor of the operon is synthesised (all-the-time - constitutively) from the i gene. The repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon”
NCERT Class 12 Biology, Ch. 5, p. 101, section 5.8
Tested in: NEET 2026 Q153, NEET 2022 Q180
Learn it: Gene Regulation Lac Operon
HGP: ESTs vs sequence annotation approaches
Tested 2 times
“One approach focused on identifying all the genes that are expressed as RNA (referred to as Expressed Sequence Tags (ESTs)”
NCERT Class 12 Biology, Ch. 5, p. 103, section 5.9
Tested in: NEET 2023 Q125, NEET 2022 Q144
Learn it: Human Genome Project
Human genome project vectors: BAC and YAC
“The commonly used hosts were bacteria and yeast, and the vectors were called as BAC (bacterial artificial chromosomes), and YAC (yeast artificial chromosomes”
NCERT Class 12 Biology, Ch. 5, p. 103, section 5.9
Tested in: NEET 2023 Q159
Learn it: rDNA Tools Restriction Ligase
Chromosome 1 has the most genes
“Chromosome 1 has most genes (2968), and the Y has the fewest (231)”
NCERT Class 12 Biology, Ch. 5, p. 104, section 5.9.1
Tested in: NEET 2025 Q169
Learn it: Human Genome Project
DNA fingerprinting targets repetitive DNA
“DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA is repeated many times”
NCERT Class 12 Biology, Ch. 5, p. 105, section 5.10
Tested in: NEET 2021 Q139
Learn it: Human Genome Project
DNA fingerprinting used Southern blot hybridisation with a VNTR probe
“DNA Fingerprinting was initially developed by Alec Jeffreys”
NCERT Class 12 Biology, Ch. 5, p. 106, section 5.10
Tested in: NEET 2021 Q168
Learn it: Health Disease Pathogens · Human Genome Project

Class 12, Chapter 6: Evolution

Printed pages 110–126. 12 lines tested by 15 questions.

Topics in this chapter (5), in NCERT order

Heckel's embryological support for evolution was disapproved by von Baer
“Embryological support for evolution was also proposed by Ernst Heckel based upon the observation of certain features during embryonic stage common to all vertebrates that are absent in adult”
NCERT Class 12 Biology, Ch. 6, p. 113, section 6.5
Tested in: NEET 2026 Q159
Learn it: Evidences Evolution
Homology/divergent vs analogy/convergent evolution
Tested 3 times
“This is divergent evolution and these structures are homologous”
NCERT Class 12 Biology, Ch. 6, p. 114, section 6.2
Tested in: NEET 2026 Q170, NEET 2025 Q109, NEET 2021 Q187
Learn it: Evidences Evolution
Evolution by anthropogenic action
Tested 2 times
“Man has bred selected plants and animals for agriculture, horticulture, sport or security”
NCERT Class 12 Biology, Ch. 6, p. 115, section 6.3
Tested in: NEET 2021 Q187, NEET 2020 Q97
Learn it: Evidences Evolution · Natural Selection Drift
Penguin and dolphin flippers are analogous, convergent
Tested 2 times
“…analogous structures are a result of convergent evolution - different structures evolving for the same function and hence having similarity”
NCERT Class 12 Biology, Ch. 6, p. 115, section 6.3
Tested in: NEET 2024 Q153, NEET 2022 Q197
Learn it: Evidences Evolution
Adaptive radiation: Darwin's finches, Australian marsupials
Tested 2 times
“This process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation. Darwin’s finches represent one of the best examples of this phenomenon”
NCERT Class 12 Biology, Ch. 6, p. 117, section 6.4
Tested in: NEET 2024 Q153, NEET 2021 Q187
Learn it: Evidences Evolution
Convergent evolution: placental mammals and Australian marsupials
“…one can call this convergent evolution. Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals”
NCERT Class 12 Biology, Ch. 6, p. 118, section 6.4
Tested in: NEET 2026 Q164
Learn it: Evidences Evolution
Hardy-Weinberg: constant gene pool vs the five disturbing factors
“This principle says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool (total genes and their alleles in a population) remains a constant. This is called genetic equilibrium”
NCERT Class 12 Biology, Ch. 6, p. 120, section 6.7
Tested in: NEET 2024 Q159
Learn it: Hardy Weinberg Principle
Stabilising, directional, disruptive natural selection
Tested 2 times
“Natural selection can lead to stabilisation (in which more individuals acquire mean character value), directional change (more individuals acquire value other than the mean character value) or disruption (more individuals acquire peripheral character value at both ends of the distribution curve)”
NCERT Class 12 Biology, Ch. 6, p. 121, section 6.6
Tested in: NEET 2026 Q141, NEET 2022 Q183
Learn it: Natural Selection Drift
Hardy-Weinberg
In short: p² + 2pq + q² = 1 (genotype frequency)
NCERT Class 12 Biology, Ch. 6, p. 121, section 6.7
Tested in: NEET 2026 Q147
Learn it: Hardy Weinberg Principle
Genetic drift by chance produces founder effect
“If the same change occurs by chance, it is called genetic drift”
NCERT Class 12 Biology, Ch. 6, p. 121, section 6.7
Tested in: NEET 2021 Q118
Learn it: Natural Selection Drift
Hominid evolution
In short: Dryopithecus → Ramapithecus → Australopithecus (3-4 mya) → Homo habilis (1.5-2 mya, tool maker) → Homo erectus (Java, 1.5 mya) → Homo neanderthalensis (1L brain) → Homo sapiens (~75 kya, Africa origin)
NCERT Class 12 Biology, Ch. 6, p. 124, section 6.10
Tested in: NEET 2024 Q155
Learn it: Hominid Evolution
Homo sapiens arose in Africa; modern Homo sapiens 75,000-10,000 years ago
“Homo sapiens arose in Africa and moved across continents and developed into distinct races”
NCERT Class 12 Biology, Ch. 6, p. 125, section 6.10
Tested in: NEET 2026 Q160
Learn it: Hominid Evolution

Class 12, Chapter 7: Human Health and Disease

Printed pages 127–148. 23 lines tested by 19 questions.

Topics in this chapter (4), in NCERT order

Health Disease Pathogensp. 1306 PYQs
Immunity Innate Acquiredp. 13410 PYQs
AIDS Cancerp. 1413 PYQs
Drugs Addictionp. 1423 PYQs

Common diseases
Tested 2 times
In short: Bacterial: typhoid (Salmonella typhi — Widal test), pneumonia (Streptococcus pneumoniae)
NCERT Class 12 Biology, Ch. 7, p. 130, section 7.1
Tested in: NEET 2024 Q177, NEET 2020 Q109
Learn it: Health Disease Pathogens
Pneumonia bacteria and malaria Plasmodium species
“Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease pneumonia in humans”
NCERT Class 12 Biology, Ch. 7, p. 131, section 7.1
Tested in: NEET 2023 Q173
Learn it: Health Disease Pathogens
Haemozoin released on RBC rupture in malaria
“The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days”
NCERT Class 12 Biology, Ch. 7, p. 131, section 7.1
Tested in: NEET 2024 Q177
Learn it: Health Disease Pathogens
Rhinoviruses cause the common cold
“Rhino viruses represent one such group of viruses which cause one of the most infectious human ailments – the common cold”
NCERT Class 12 Biology, Ch. 7, p. 131, section 7.1
Tested in: NEET 2024 Q177
Learn it: Health Disease Pathogens
Ringworm fungi and filarial worm species
Tested 2 times
“…fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton are responsible for ringworms”
NCERT Class 12 Biology, Ch. 7, p. 133, section 7.1
Tested in: NEET 2023 Q173, NEET 2020 Q109
Learn it: Health Disease Pathogens
Immunity
Tested 4 times
In short: Innate (non-specific): physical (skin), physiological (acid pH), cellular (NK cells, macrophages), cytokine
NCERT Class 12 Biology, Ch. 7, p. 134, section 7.2
Tested in: NEET 2025 Q118, NEET 2024 Q175, NEET 2022 Q186, NEET 2020 Q131
Learn it: Immunity Innate Acquired
Colostrum has abundant IgA antibodies (passive immunity)
Tested 2 times
“The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant”
NCERT Class 12 Biology, Ch. 7, p. 136, section 7.2.3
Tested in: NEET 2026 Q171, NEET 2024 Q175
Learn it: Immunity Innate Acquired · Fertilization Pregnancy
Active immunity is slow; passive immunity is ready-made antibodies
“When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity”
NCERT Class 12 Biology, Ch. 7, p. 136, section 7.2.3
Tested in: NEET 2020 Q131
Learn it: Immunity Innate Acquired
Allergy definition; dust mites as allergen
“The exaggerated response of the immune system to certain antigens present in the environment is called allergy”
NCERT Class 12 Biology, Ch. 7, p. 137, section 7.2.5
Tested in: NEET 2024 Q177
Learn it: Health Disease Pathogens
Auto-immune disease definition; rheumatoid arthritis example
“…the body attacks self-cells. This results in damage to the body and is called auto-immune disease”
NCERT Class 12 Biology, Ch. 7, p. 137, section 7.2.6
Tested in: NEET 2022 Q179
Learn it: Immunity Innate Acquired
Primary and secondary lymphoid organs
Tested 2 times
“The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate”
NCERT Class 12 Biology, Ch. 7, p. 137, section 7.2.7
Tested in: NEET 2026 Q165, NEET 2025 Q124
Learn it: Immunity Innate Acquired
Bone marrow and thymus roles in lymphocyte development
“The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced”
NCERT Class 12 Biology, Ch. 7, p. 138, section 7.2.7
Tested in: NEET 2024 Q191
Learn it: Immunity Innate Acquired
ELISA test used for AIDS diagnosis
“A widely used diagnostic test for AIDS is enzyme linked immuno-sorbent assay (ELISA)”
NCERT Class 12 Biology, Ch. 7, p. 140, section 7.3
Tested in: NEET 2021 Q168
Learn it: Health Disease Pathogens
HIV replicates in helper T-lymphocytes
“Simultaneously, HIV enters into helper T-lymphocytes (TH ), replicates and produce progeny viruses”
NCERT Class 12 Biology, Ch. 7, p. 140, section 7.3
Tested in: NEET 2023 Q152
Learn it: AIDS Cancer
Anti-retroviral treatment of AIDS is only partially effective
“Treatment of AIDS with anti-retroviral drugs is only partially effective”
NCERT Class 12 Biology, Ch. 7, p. 140, section 7.3
Tested in: NEET 2026 Q177
Learn it: Drugs Addiction
CT and MRI detect internal organ cancers
“Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs”
NCERT Class 12 Biology, Ch. 7, p. 141, section 7.4
Tested in: NEET 2025 Q155
Learn it: AIDS Cancer
Leukemia diagnosis: increased blood/bone marrow cell counts
“…blood and bone marrow tests for increased cell counts in the case of leukemias”
NCERT Class 12 Biology, Ch. 7, p. 141, section 7.4
Tested in: NEET 2025 Q155
Learn it: AIDS Cancer
Malignant tumor cell characteristics
“The malignant tumors, on the other hand are a mass of proliferating cells called neoplastic or tumor cells”
NCERT Class 12 Biology, Ch. 7, p. 141, section 7.4
Tested in: NEET 2025 Q140
Learn it: AIDS Cancer
Chemotherapy kills cancerous cells; interferon as biological response modifier
“Several chemotherapeutic drugs are used to kill cancerous cells”
NCERT Class 12 Biology, Ch. 7, p. 142, section 7.4
Tested in: NEET 2025 Q155
Learn it: AIDS Cancer
Heroin depressant; cannabinoid cardiovascular effects
“…heroin is a depressant and slows down body functions”
NCERT Class 12 Biology, Ch. 7, p. 143, section 7.5
Tested in: NEET 2023 Q172
Learn it: Drugs Addiction
Cocaine-dopamine interference; morphine as surgical sedative
Tested 3 times
“It interferes with the transport of the neuro-transmitter dopamine”
NCERT Class 12 Biology, Ch. 7, p. 143, section 7.5
Tested in: NEET 2026 Q177, NEET 2024 Q168, NEET 2023 Q172
Learn it: Drugs Addiction
Cocaine source: Erythroxylum coca
“Coca alkaloid or cocaine is obtained from coca plant Erythroxylum coca, native to South America”
NCERT Class 12 Biology, Ch. 7, p. 143, section 7.5
Tested in: NEET 2024 Q168
Learn it: Drugs Addiction
Cannabis sativa and Papaver somniferum as drug source plants
“Natural cannabinoids are obtained from the inflorescences of the plant Cannabis sativa”
NCERT Class 12 Biology, Ch. 7, p. 143, section 7.5
Tested in: NEET 2024 Q168
Learn it: Drugs Addiction

Class 12, Chapter 8: Microbes in Human Welfare

Printed pages 149–160. 4 lines tested by 7 questions.

Topics in this chapter (3), in NCERT order

Microbes Household Industrialp. 1516 PYQs
Microbes Sewage Biogasp. 1541 PYQ
Biocontrol Biofertilizersp. 1571 PYQ

Fermented beverages: distilled and non-distilled
“Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth”
NCERT Class 12 Biology, Ch. 8, p. 152, section 9.2.1
Tested in: NEET 2025 Q158
Learn it: Microbes Household Industrial
Bioactive molecules: streptokinase, cyclosporin A, statins
Tested 4 times
“Examples of acid producers are Aspergillus niger (a fungus) of citric acid, Acetobacter aceti (a bacterium) of acetic acid; Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid”
NCERT Class 12 Biology, Ch. 8, p. 153, section 9.2.3
Tested in: NEET 2026 Q136, NEET 2025 Q137, NEET 2024 Q113, NEET 2022 Q166
Learn it: Microbes Household Industrial
Sewage & biogas
In short: Sewage treatment: primary (sedimentation), secondary (aerobic — flocs of microbes
NCERT Class 12 Biology, Ch. 8, p. 154, section 9.4
Tested in: NEET 2020 Q120
Learn it: Microbes Sewage Biogas
Cyanobacteria fix nitrogen as biofertiliser
“Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc”
NCERT Class 12 Biology, Ch. 8, p. 158, section 9.6
Tested in: NEET 2025 Q175
Learn it: Biocontrol Biofertilizers

Class 12, Chapter 9: Biotechnology — Principles and Processes

Printed pages 161–176. 20 lines tested by 21 questions.

Topics in this chapter (3), in NCERT order

rDNA Principlesp. 1643 PYQs
rDNA Tools Restriction Ligasep. 16515 PYQs
rDNA Process PCR Blottingp. 16810 PYQs

Hind II recognition sequence is six base pairs
“It was found that Hind II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs”
NCERT Class 12 Biology, Ch. 9, p. 165, section 9.2.1
Tested in: NEET 2024 Q103
Learn it: rDNA Tools Restriction Ligase
Tools
Tested 3 times
In short: Restriction enzymes (EcoRI — palindromic site GAATTC, sticky ends)
NCERT Class 12 Biology, Ch. 9, p. 165, section 10.2
Tested in: NEET 2023 Q159, NEET 2022 Q107, NEET 2020 Q112
Learn it: rDNA Tools Restriction Ligase · rDNA Process PCR Blotting
Restriction endonuclease recognises palindromic sequence
Tested 2 times
“Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA”
NCERT Class 12 Biology, Ch. 9, p. 166, section 9.2.1
Tested in: NEET 2022 Q154, NEET 2020 Q115
Learn it: rDNA Tools Restriction Ligase
Exonucleases remove end nucleotides; endonucleases cut within DNA
“Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA”
NCERT Class 12 Biology, Ch. 9, p. 166, section 9.2.1
Tested in: NEET 2020 Q133
Learn it: rDNA Tools Restriction Ligase
Restriction enzymes cut away from palindrome centre
“Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands”
NCERT Class 12 Biology, Ch. 9, p. 167, section 9.2.1
Tested in: NEET 2022 Q154
Learn it: rDNA Tools Restriction Ligase
DNA visualised by ethidium bromide under UV
Tested 3 times
“The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation”
NCERT Class 12 Biology, Ch. 9, p. 168, section 9.2.1
Tested in: NEET 2023 Q105, NEET 2022 Q111, NEET 2020 Q124
Learn it: rDNA Process PCR Blotting
Gel electrophoresis: smaller fragments move farther
“Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field”
NCERT Class 12 Biology, Ch. 9, p. 168, section 9.2.1
Tested in: NEET 2025 Q95
Learn it: rDNA Process PCR Blotting
PCR, blotting, electrophoresis
Tested 2 times
In short: PCR: denature 94°C → anneal 50-65°C → extend 72°C with Taq pol
NCERT Class 12 Biology, Ch. 9, p. 168, section 10.3
Tested in: NEET 2026 Q162, NEET 2022 Q107
Learn it: rDNA Process PCR Blotting
Origin of replication (ori) controls copy number
“This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells”
NCERT Class 12 Biology, Ch. 9, p. 169, section 9.2
Tested in: NEET 2020 Q115
Learn it: rDNA Tools Restriction Ligase
Cloning vector needs single restriction site
“…the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes”
NCERT Class 12 Biology, Ch. 9, p. 169, section 9.2
Tested in: NEET 2022 Q196
Learn it: rDNA Tools Restriction Ligase
rop gene codes for plasmid replication proteins
“…rop codes for the proteins involved in the replication of the plasmid”
NCERT Class 12 Biology, Ch. 9, p. 169, section 9.2.2
Tested in: NEET 2023 Q159
Learn it: rDNA Tools Restriction Ligase
Chromogenic substrate gives blue colonies, not DNA bands
Tested 3 times
“The presence of a chromogenic substrate gives blue coloured colonies if the plasmid in the bacteria does not have an insert”
NCERT Class 12 Biology, Ch. 9, p. 170, section 9.2.2
Tested in: NEET 2025 Q101, NEET 2025 Q173, NEET 2022 Q111
Learn it: rDNA Tools Restriction Ligase · rDNA Process PCR Blotting
Ti plasmid of Agrobacterium is tumour inducing
“The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector which is no more pathogenic to the plants”
NCERT Class 12 Biology, Ch. 9, p. 170, section 9.2.2
Tested in: NEET 2024 Q167
Learn it: rDNA Tools Restriction Ligase
Gene gun/biolistics uses gold or tungsten particles
“…cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun”
NCERT Class 12 Biology, Ch. 9, p. 171, section 9.2.3
Tested in: NEET 2023 Q128
Learn it: Biotech Agriculture Bt GM
Chilled ethanol precipitates purified DNA
Tested 2 times
“…purified DNA ultimately precipitates out after the addition of chilled ethanol”
NCERT Class 12 Biology, Ch. 9, p. 171, section 9.3.1
Tested in: NEET 2023 Q117, NEET 2021 Q121
Learn it: rDNA Principles · Plant Kingdom
PCR: polymerase chain reaction; three steps per cycle
Tested 2 times
In short: PCR stands for Polymerase Chain Reaction
NCERT Class 12 Biology, Ch. 9, p. 172, section 9.3.1
Tested in: NEET 2026 Q162, NEET 2022 Q107
Learn it: rDNA Process PCR Blotting
PCR amplifies DNA through repeated replication cycles
“If the process of replication of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times, i.e., 1 billion copies are made”
NCERT Class 12 Biology, Ch. 9, p. 173, section 9.3.3
Tested in: NEET 2022 Q148
Learn it: rDNA Process PCR Blotting
PCR extension: the enzyme extends the primers on the genomic DNA template
“The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as template”
NCERT Class 12 Biology, Ch. 9, p. 173, section 9.3.3
Tested in: NEET 2026 Q162
Learn it: rDNA Process PCR Blotting
Ampicillin resistance gene is a selectable marker
“Since, due to ampicillin resistance gene, one is able to select a transformed cell in the presence of ampicillin”
NCERT Class 12 Biology, Ch. 9, p. 173, section 9.3.3
Tested in: NEET 2022 Q107
Learn it: rDNA Process PCR Blotting
Bioreactors: large-scale culture with control systems
“To produce in large quantities, the development of bioreactors, where large volumes (100-1000 litres) of culture can be processed, was required”
NCERT Class 12 Biology, Ch. 9, p. 174, section 9.3.5
Tested in: NEET 2024 Q174
Learn it: rDNA Process PCR Blotting

Class 12, Chapter 10: Biotechnology and its Applications

Printed pages 177–187. 7 lines tested by 9 questions.

Topics in this chapter (3), in NCERT order

Biotech Agriculture Bt GMp. 1804 PYQs
Biotech Medicine Insulinp. 1829 PYQs
Transgenic Animals Biopiracyp. 1840 PYQs

RNAi silencing via complementary dsRNA
“This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA”
NCERT Class 12 Biology, Ch. 10, p. 180, section 10.1
Tested in: NEET 2025 Q131
Learn it: Biotech Agriculture Bt GM
RNAi is a method of cellular defence
“RNAi takes place in all eukaryotic organisms as a method of cellular defense”
NCERT Class 12 Biology, Ch. 10, p. 180, section 10.1
Tested in: NEET 2025 Q160
Learn it: Transcription Translation · Biotech Medicine Insulin
Transposons as source of RNA triggering RNAi silencing
“The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate”
NCERT Class 12 Biology, Ch. 10, p. 180, section 10.1
Tested in: NEET 2022 Q148
Learn it: rDNA Process PCR Blotting
Insulin C-peptide and A/B chain disulfide bonds
“This C peptide is not present in the mature insulin and is removed during maturation into insulin”
NCERT Class 12 Biology, Ch. 10, p. 182, section 10.2.1
Tested in: NEET 2021 Q169
Learn it: Biotech Medicine Insulin
Serum/urine analysis does not allow early diagnosis
Tested 2 times
“Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is”
NCERT Class 12 Biology, Ch. 10, p. 182, section 10.2.3
Tested in: NEET 2023 Q184, NEET 2021 Q168
Learn it: Biotech Medicine Insulin · Health Disease Pathogens
Biotech in medicine
Tested 3 times
In short: Recombinant insulin: Eli Lilly 1983 (Humulin) — A + B chains in E
NCERT Class 12 Biology, Ch. 10, p. 182, section 11.3
Tested in: NEET 2025 Q165, NEET 2022 Q190, NEET 2021 Q193
Learn it: Biotech Medicine Insulin
Radioactive probe detected by autoradiography
Tested 2 times
“A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography”
NCERT Class 12 Biology, Ch. 10, p. 183, section 10.2.3
Tested in: NEET 2022 Q148, NEET 2021 Q168
Learn it: rDNA Process PCR Blotting · Health Disease Pathogens

Class 12, Chapter 11: Organisms and Populations

Printed pages 188–204. 10 lines tested by 16 questions.

Topics in this chapter (2), in NCERT order

Population Attributes Growthp. 1948 PYQs
Population Interactionsp. 19712 PYQs

Population attributes: rates, sex ratio, age pyramid
“An individual may have births and deaths, but a population has birth rates and death rates”
NCERT Class 12 Biology, Ch. 11, p. 191, section 11.1.1
Tested in: NEET 2020 Q132
Learn it: Population Attributes Growth
Death rate is deaths per capita per period
“If 4 individuals in a laboratory population of 40 fruitflies died during a specified time interval, say a week, the death rate in the population during that period is 4/40 = 0.1 individuals per fruitfly per week”
NCERT Class 12 Biology, Ch. 11, p. 191, section 11.1.1
Tested in: NEET 2022 Q169
Learn it: Population Attributes Growth
Natality and mortality defined
“Natality refers to the number of births during a given period in the population that are added to the initial density”
NCERT Class 12 Biology, Ch. 11, p. 193, section 12.1
Tested in: NEET 2020 Q132
Learn it: Population Attributes Growth
Integral exponential growth equation Nt=N0ert
“…you can derive the integral form of the exponential growth equation as Nt = N0 ert where Nt = Population density after time t”
NCERT Class 12 Biology, Ch. 11, p. 194, section 11.1.2
Tested in: NEET 2021 Q140
Learn it: Population Attributes Growth
Population growth
Tested 3 times
In short: Exponential: dN/dt = rN
NCERT Class 12 Biology, Ch. 11, p. 194, section 12.4
Tested in: NEET 2025 Q112, NEET 2024 Q114, NEET 2023 Q187
Learn it: Population Attributes Growth
Population interactions
Tested 7 times
In short: Predation, competition (Gause's competitive exclusion principle), parasitism (+, −), mutualism (+, +
NCERT Class 12 Biology, Ch. 11, p. 197, section 12.5
Tested in: NEET 2026 Q174, NEET 2025 Q178, NEET 2023 Q144, NEET 2022 Q120, NEET 2022 Q147, NEET 2021 Q128, NEET 2021 Q135
Learn it: Population Interactions
Gause's Competitive Exclusion Principle
Tested 2 times
“Gause's 'Competitive Exclusion Principle' states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually”
NCERT Class 12 Biology, Ch. 11, p. 199, section 11.1.4
Tested in: NEET 2024 Q186, NEET 2023 Q147
Learn it: Population Interactions
Resource partitioning avoids competition
“…species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism”
NCERT Class 12 Biology, Ch. 11, p. 199, section 11.1.4
Tested in: NEET 2021 Q128
Learn it: Population Interactions
Brood parasitism: cuckoo lays eggs in host nest
“Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them”
NCERT Class 12 Biology, Ch. 11, p. 200, section 11.1.4
Tested in: NEET 2023 Q185
Learn it: Population Interactions
Commensalism: orchid on a mango branch, barnacles on a whale
“Commensalism: This is the interaction in which one species benefits and the other is neither harmed nor benefited”
NCERT Class 12 Biology, Ch. 11, p. 201, section 11.1.4
Tested in: NEET 2025 Q178
Learn it: Population Interactions

Class 12, Chapter 12: Ecosystem

Printed pages 205–215. 8 lines tested by 9 questions.

Topics in this chapter (2), in NCERT order

Ecosystem Structure Functionp. 2064 PYQs
Ecosystem Productivity Decompositionp. 20711 PYQs

Productivity, decomposition, energy flow
Tested 5 times
In short: GPP > NPP (NPP = GPP − R)
NCERT Class 12 Biology, Ch. 12, p. 207, section 12.2
Tested in: NEET 2026 Q178, NEET 2025 Q147, NEET 2024 Q143, NEET 2023 Q121, NEET 2020 Q113
Learn it: Ecosystem Productivity Decomposition
Productivity units: g/energy per area per year
“The rate of biomass production is called productivity”
NCERT Class 12 Biology, Ch. 12, p. 207, section 12.2
Tested in: NEET 2025 Q91
Learn it: Ecosystem Productivity Decomposition
Decomposition rate vs lignin/chitin content
“Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism”
NCERT Class 12 Biology, Ch. 12, p. 207, section 12.3
Tested in: NEET 2022 Q128
Learn it: Ecosystem Productivity Decomposition
Fragmentation, leaching, mineralisation steps
“Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation”
NCERT Class 12 Biology, Ch. 12, p. 207, section 12.3
Tested in: NEET 2022 Q168
Learn it: Ecosystem Productivity Decomposition
Energy flow unidirectional; not exempt from 2nd law
Tested 2 times
“So you find unidirectional flow of energy from the sun to producers and then to consumers”
NCERT Class 12 Biology, Ch. 12, p. 209, section 12.4
Tested in: NEET 2026 Q178, NEET 2025 Q108
Learn it: Ecosystem Productivity Decomposition
Sun is the only energy source except deep-sea hydrothermal ecosystems; PAR under 50 per cent
Tested 2 times
“Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth”
NCERT Class 12 Biology, Ch. 12, p. 209, section 12.4
Tested in: NEET 2025 Q147, NEET 2023 Q121
Learn it: Ecosystem Productivity Decomposition
10 per cent law of energy transfer between trophic levels
Tested 2 times
“The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law - only 10 per cent of the energy is transferred to each trophic level from the lower trophic level”
NCERT Class 12 Biology, Ch. 12, p. 211, section 12.4
Tested in: NEET 2026 Q178, NEET 2024 Q143
Learn it: Ecosystem Productivity Decomposition
Pyramid of energy is always upright
“Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step”
NCERT Class 12 Biology, Ch. 12, p. 213, section 12.4
Tested in: NEET 2026 Q178
Learn it: Ecosystem Productivity Decomposition

Class 12, Chapter 13: Biodiversity and Conservation

Printed pages 216–227. 15 lines tested by 14 questions.

Topics in this chapter (2), in NCERT order

Biodiversity Patternsp. 2195 PYQs
Biodiversity Loss Conservationp. 22410 PYQs

Robert May estimate: 7 million global species
Tested 2 times
“…a more conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million”
NCERT Class 12 Biology, Ch. 13, p. 217, section 13.1.1
Tested in: NEET 2024 Q137, NEET 2020 Q104
Learn it: Biodiversity Patterns
Species described (IUCN 2004) vs extreme estimates of 20 to 50 million
Tested 2 times
“(IUCN) (2004), the total number of plant and animal species described so far is slightly more than 1.5 million”
NCERT Class 12 Biology, Ch. 13, p. 217, section 13.1.1
Tested in: NEET 2024 Q121, NEET 2020 Q104
Learn it: Biodiversity Patterns · Biodiversity Loss Conservation
Amazon rain forest has greatest biodiversity on earth
Tested 2 times
“The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth”
NCERT Class 12 Biology, Ch. 13, p. 219, section 13.1.2
Tested in: NEET 2026 Q144, NEET 2020 Q129
Learn it: Biodiversity Patterns
Why tropics show greatest species richness
“…tropical latitudes have remained relatively undisturbed for millions of years”
NCERT Class 12 Biology, Ch. 13, p. 219, section 13.1.2
Tested in: NEET 2024 Q127
Learn it: Biodiversity Patterns
Humboldt: species richness rises with area
“…the great German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit”
NCERT Class 12 Biology, Ch. 13, p. 220, section 13.1.2
Tested in: NEET 2024 Q137
Learn it: Biodiversity Patterns
Paul Ehrlich's rivet popper hypothesis
“…we can develop a proper perspective through an analogy (the ‘rivet popper hypothesis’) used by Stanford ecologist Paul Ehrlich”
NCERT Class 12 Biology, Ch. 13, p. 221, section 13.1.3
Tested in: NEET 2024 Q137
Learn it: Biodiversity Patterns
Tilman's outdoor-plot ecosystem experiments
“David Tilman’s long-term ecosystem experiments using outdoor plots provide some tentative answers”
NCERT Class 12 Biology, Ch. 13, p. 221, section 13.1.3
Tested in: NEET 2024 Q137
Learn it: Biodiversity Patterns
IUCN Red List (2004): 784 extinctions in 500 years
“The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years”
NCERT Class 12 Biology, Ch. 13, p. 221, section 13.1.3
Tested in: NEET 2024 Q121
Learn it: Biodiversity Loss Conservation
Dodo is an example of recent extinction
“Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller’s Sea Cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger”
NCERT Class 12 Biology, Ch. 13, p. 221, section 13.1.4
Tested in: NEET 2025 Q125
Learn it: Biodiversity Loss Conservation
Evil Quartet: four causes of biodiversity loss
Tested 4 times
“Causes of biodiversity losses: The accelerated rates of species extinctions that the world is facing now are largely due to human activities”
NCERT Class 12 Biology, Ch. 13, p. 222, section 13.1.4
Tested in: NEET 2025 Q125, NEET 2024 Q118, NEET 2023 Q104, NEET 2022 Q131
Learn it: Biodiversity Loss Conservation
Lantana is an invasive alien species
“…environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia)”
NCERT Class 12 Biology, Ch. 13, p. 223, section 13.1.4
Tested in: NEET 2025 Q125
Learn it: Biodiversity Loss Conservation
Conservation
Tested 4 times
In short: In situ: national parks, biosphere reserves (e.g
NCERT Class 12 Biology, Ch. 13, p. 224, section 13.2
Tested in: NEET 2025 Q125, NEET 2025 Q171, NEET 2024 Q121, NEET 2022 Q118
Learn it: Biodiversity Loss Conservation
In situ vs ex situ conservation defined
“When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected - we save the entire forest to save the tiger. This approach is called in situ (on site) conservation”
NCERT Class 12 Biology, Ch. 13, p. 224, section 13.2.2
Tested in: NEET 2022 Q173
Learn it: Biodiversity Loss Conservation
Earth Summit Rio 1992 Convention on Biological Diversity
“The historic Convention on Biological Diversity (‘The Earth Summit’) held in Rio de Janeiro in 1992, called upon all nations to take appropriate measures for conservation of biodiversity and sustainable utilisation of its benefits”
NCERT Class 12 Biology, Ch. 13, p. 225, section 13.2.2
Tested in: NEET 2023 Q108
Learn it: Biodiversity Loss Conservation
In situ and ex situ conservation efforts (summary)
Tested 2 times
“Our country's in situ conservation efforts are reflected in its 14 biosphere reserves, 90 national parks, > 450 wildlife sanctuaries and many sacred groves”
NCERT Class 12 Biology, Ch. 13, p. 226, section 13.2.2
Tested in: NEET 2025 Q171, NEET 2022 Q118
Learn it: Biodiversity Loss Conservation

Class 12 (pre-2023 edition), Chapter 9: Strategies for Enhancement in Food Production

Printed pages 165–178. 5 lines tested by 4 questions. This chapter is not in the current (2023 rationalised) NCERT book; pages are from the pre-2023 edition.

Inbreeding raises homozygosity and accumulates superior genes
“Inbreeding increases homozygosity. Thus inbreeding is necessary if we want to evolve a pureline in any animal. Inbreeding exposes harmful recessive genes that are eliminated by selection”
NCERT Class 12 Biology (pre-2023 edition), Ch. 9, p. 167, section 9.1.2
Tested in: NEET 2023 Q200
Continued close inbreeding causes inbreeding depression
“…continued inbreeding, especially close inbreeding, usually reduces fertility and even productivity. This is called inbreeding depression”
NCERT Class 12 Biology (pre-2023 edition), Ch. 9, p. 167, section 9.1.2
Tested in: NEET 2023 Q200
Mutation breeding uses chemicals or gamma radiation
“Mutation is the process by which genetic variations are created through changes in the base sequence within genes”
NCERT Class 12 Biology (pre-2023 edition), Ch. 9, p. 174, section 9.2.2
Tested in: NEET 2021 Q134
Learn it: Mutations Genetic Disorders
SCP & tissue culture
In short: Single-cell protein: Spirulina, Methylophilus methylotrophus — protein source
NCERT Class 12 Biology (pre-2023 edition), Ch. 9, p. 176, section 8.5
Tested in: NEET 2024 Q106
Biofortification defined
“Biofortification – breeding crops with higher levels of vitamins and minerals, or higher protein and healthier fats – is the most practical means to improve public health”
NCERT Class 12 Biology (pre-2023 edition), Ch. 9, p. 176, section 9.2.4
Tested in: NEET 2022 Q165

Class 12 (pre-2023 edition), Chapter 16: Environmental Issues

Printed pages 270–286. 6 lines tested by 5 questions. This chapter is not in the current (2023 rationalised) NCERT book; pages are from the pre-2023 edition.

Electrostatic precipitator removes particulate matter
Tested 2 times
“…the most widely used of which is the electrostatic precipitator (Figure 16.1), which can remove over 99 per cent particulate matter present in the exhaust from a thermal power plant”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 271, section 16.1
Tested in: NEET 2023 Q179, NEET 2022 Q102
Electrostatic precipitator mechanism
“It has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 271, section 16.1
Tested in: NEET 2023 Q179
Incinerators for hospital waste; e-wastes landfilled or incinerated
“The use of incinerators is crucial to disposal of hospital waste”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 279, section 16.3
Tested in: NEET 2022 Q102
Ozone thickness measured in Dobson units
“The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU)”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 282, section 16.7
Tested in: NEET 2023 Q110
UV-B causes snow-blindness and skin cancer
“UV-B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 283, section 16.7
Tested in: NEET 2020 Q117
Montreal Protocol 1987 controls ozone depleters
“…an international treaty, known as the Montreal Protocol, was signed at Montreal (Canada) in 1987 (effective in 1989) to control the emission of ozone depleting substances”
NCERT Class 12 Biology (pre-2023 edition), Ch. 16, p. 283, section 16.7
Tested in: NEET 2020 Q101

Questions about this list

Which Class 12 NCERT Biology lines has NEET asked about more than once?: 68 of the 220 lines on this page were tested by two or more questions. The most tested: Population interactions (NCERT Class 12 Biology, Ch. 11, p. 197; 7 questions, 2021, 2022, 2023, 2025, 2026); Productivity, decomposition, energy flow (NCERT Class 12 Biology, Ch. 12, p. 207; 5 questions, 2020, 2023, 2024, 2025, 2026); Conservation (NCERT Class 12 Biology, Ch. 13, p. 224; 4 questions, 2022, 2024, 2025); Evil Quartet: four causes of biodiversity loss (NCERT Class 12 Biology, Ch. 13, p. 222; 4 questions, 2022, 2023, 2024, 2025); Immunity (NCERT Class 12 Biology, Ch. 7, p. 134; 4 questions, 2020, 2022, 2024, 2025).
How were these NCERT lines chosen?: Each line is an Class 12 NCERT Biology passage that a NEET question from 2020 to 2026 was matched to directly: the question can be answered from that line. 220 lines across 15 chapters, tied to 225 questions. The count covers the questions matched to our NCERT extract, which does not yet hold every page of the book, so a line missing here may still have been tested.
Which page numbers are these?: The page number printed in the NCERT book, not the page of a PDF file. Chapters are numbered as the current (2023 rationalised) edition prints them; a chapter that edition dropped is marked pre-2023 edition.
Which Class 12 NCERT Biology chapter has the most lines NEET tested?: Molecular Basis of Inheritance (Class 12, Chapter 5): 35 lines, tied to 40 questions.

Question numbers are those of the test-booklet code we hold for each year (2020 H3, 2021 P3, 2022 R6, 2023 F3, 2024 Q3, 2025 47, 2026 50). Solve them on the Biology practice page, see both classes' chapters, or go back to all Biology units. Found a mistake? It will be fixed and listed in the corrections log.

NCERT line-by-line Biology Class 12 for NEET: the lines NEET tested

Class 12, Chapter 1: Sexual Reproduction in Flowering Plants

Angiosperm anther: bilobed, two theca per lobe (dithecous)

Tapetum nourishes pollen; its cells often have more than one nucleus

Pollen grain is the male gametophyte

Pollen viability duration varies by species

Embryo sac is the female gametophyte in nucellus

MMC: one meiosis then three mitoses form embryo sac

Egg apparatus vs polar nuclei in embryo sac

Filiform apparatus of synergids guides the pollen tube

Xenogamy: pollen to a different plant's stigma

Cleistogamous flowers are invariably autogamous

Wind/water pollination produces enormous pollen

Pollination & double fertilization

Corn cob stigma-style waves in wind to trap pollen

Water pollination: waterlily, mucilage, ribbon pollen

Wind and water pollinated flowers lack colour and nectar

Wind-pollinated flowers have well-exposed stamens

Insect-pollinated flowers are large, colourful, nectar-rich

Double fertilisation: diploid zygote, triploid primary endosperm nucleus

False fruit forms when thalamus contributes

Non-albuminous seeds and perisperm defined

Class 12, Chapter 2: Human Reproduction

Vas deferens: seminal vesicle duct, ejaculatory duct

Male sex accessory ducts: rete testis, vasa efferentia, epididymis, vas deferens

Female reproductive system

Fallopian tube regions: infundibulum, ampulla, isthmus

Hymen not a reliable indicator of virginity

Cervical canal with vagina forms birth canal

Spermiogenesis and spermiation defined

LH-Leydig-androgens; FSH-Sertoli-spermiogenesis

Oogenesis begins in embryo; spermatogenesis at puberty

Sperm structure: nucleus, acrosome, mitochondria, tail

Oogenesis starts in the embryo; no oogonia added after birth

Menarche; missed menstruation may indicate pregnancy

Graafian follicle ruptures to release the secondary oocyte (ovulation)

Secondary oocyte forms the zona pellucida around it

Cyclic menstruation spans menarche to menopause

LH and FSH stimulate follicles to secrete estrogen

Endometrium needed for implantation; corpus luteum degeneration

LH and FSH stimulate follicular development

LH surge causes ovulation; corpus luteum secretes progesterone

Fertilisation: zona pellucida contact completes oocyte meiosis

Relaxin secreted by ovary in late pregnancy

Embryonic development timeline: heart, limbs, organs, hair

Class 12, Chapter 3: Reproductive Health

Statutory ban on amniocentesis for sex-determination

Contraception methods

IUD types: non-medicated, copper, hormone releasing

Barrier methods block cervix (diaphragm, caps, vaults)

IUDs increase phagocytosis of sperms in uterus

Lactational amenorrhea prevents ovulation after parturition

Withdrawal/coitus interruptus is a natural method

Implants deliver progestogens under the skin

Contraceptive pills inhibit ovulation and implantation

Surgical sterilisation: vasectomy (male), tubectomy (female)

Saheli is an oral non-steroidal contraceptive

Vasectomy removes vas deferens; tubectomy removes fallopian tube

STDs & infertility

Gonorrhoea is a curable STI

Amniocentesis & ART

Class 12, Chapter 4: Principles of Inheritance and Variation

Mendel's 14 varieties, 7 characters

Punnett square diagram

Mendel's laws

Law of Dominance statements

Inheritance patterns

ABO alleles: i produces no sugar

Sturtevant maps genes via recombination frequency

Linkage & crossing over

9:3:3:1 is the F2 ratio expected when two genes are independent

Pleiotropy: one gene, multiple phenotypic expression

XO sex determination in grasshopper

Genetic disorders

Colour Blindness

Pedigree examples: dominant vs recessive trait

Colour Blindness (continued)

Chromosome locations: Klinefelter, Thalassemia genes

Down's syndrome: trisomy 21, palm crease

Klinefelter's syndrome: 47, XXY; masculine with gynaecomastia; sterile