The NEET trap in reproductive health is confusing which STD is caused by which pathogen, confusing viral vs. bacterial STDs (treatment implications), and mixing up infertility causes between male and female factors.
Sexually Transmitted Diseases (STDs) / Sexually Transmitted Infections (STIs):
NCERT Class 12 Biology Chapter 4 (Reproductive Health), page 56 onwards, categorises STDs by causative agent:
Key distinction for NEET: bacterial STDs are curable with antibiotics; viral STDs (HIV, herpes, hepatitis B, HPV) are incurable — only manageable.
Infertility:
Infertility is the inability to conceive after one year of unprotected intercourse. Causes include — male: low sperm count, abnormal morphology, erectile dysfunction; female: tubal blockage, anovulation, endometriosis, uterine anomalies. Both partners must be evaluated.
Assisted Reproductive Technologies (ART): IVF (in vitro fertilisation), ZIFT (zygote intrafallopian transfer — zygote up to 8 blastomeres placed in fallopian tube), GIFT (gamete intrafallopian transfer — ovum from donor + sperm placed in tube of female who cannot produce ova but can provide conditions for fertilisation and development), ICSI (intracytoplasmic sperm injection — for low sperm count), AI (artificial insemination — semen collected and introduced into vagina/uterus).
Watch-out: ZIFT transfers a zygote/early embryo into the fallopian tube; IUT (intra-uterine transfer) transfers embryos with >8 blastomeres into the uterus. Don't swap these.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which of the following STDs is caused by a protozoan?
Answer: A. Trichomoniasis is caused by Trichomonas vaginalis, a flagellated protozoan (NCERT Class 12 Biology, Chapter 4, page 56).
Why B is wrong: B is wrong — Syphilis is bacterial (Treponema pallidum), a spirochaete.
Why C is wrong: C is wrong — Gonorrhoea is bacterial (Neisseria gonorrhoeae), commonly confused because both affect the urogenital tract.
Why D is wrong: D is wrong — Genital herpes is viral (HSV-2). Viral vs. protozoan pathogen category is a frequent NEET trap.
Which of the following STDs is incurable and can only be managed symptomatically?
Answer: D. Genital herpes is caused by HSV-2 (a virus); viral STDs have no cure — only antiviral management (NCERT Class 12 Biology, Chapter 4).
Why A is wrong: A is wrong — Chlamydiasis is bacterial (Chlamydia trachomatis); treatable with antibiotics like azithromycin.
Why B is wrong: B is wrong — Gonorrhoea is bacterial; curable with appropriate antibiotic therapy.
Why C is wrong: C is wrong — Syphilis is bacterial (Treponema pallidum); curable with penicillin.
In GIFT (Gamete Intra-Fallopian Transfer), what is transferred into the fallopian tube?
Answer: B. GIFT involves transfer of an ovum from a donor female and sperm into the fallopian tube of a female who cannot produce ova but can provide conditions for fertilisation and further development (NCERT Class 12 Biology, Chapter 4).
Why A is wrong: A is wrong — Transfer of zygote/early embryo (up to 8 blastomeres) into the fallopian tube describes ZIFT, not GIFT.
Why C is wrong: C is wrong — Embryos with >8 blastomeres are transferred into the uterus (IUT — intra-uterine transfer), not fallopian tube.
Why D is wrong: D is wrong — Transfer of only sperm into the reproductive tract describes artificial insemination (AI/IUI), not GIFT.
A couple has been infertile for 2 years. The male partner has a very low sperm count in the ejaculate, but sperm morphology is normal. Which technique does NCERT name for exactly this indication?
Answer: C. NCERT states it in one sentence: "Infertility cases either due to inability of the male partner to inseminate the female or due to very low sperm counts in the ejaculates, could be corrected by artificial insemination (AI) technique" (NCERT Class 12 Biology, Chapter 3, page 48). Semen is collected — from the husband or a donor — and introduced into the vagina or uterus (IUI). The stem uses NCERT's own phrase "very low sperm count in the ejaculate", which is the cue for AI.
Why A is wrong: A is wrong — GIFT requires collection of gametes and transfer into the fallopian tube; it does not specifically address extremely low count since it still needs adequate sperm for in-vivo fertilisation.
Why B is wrong: B is wrong — Standard IVF requires incubation of sperm with ova in vitro; with extremely low count, conventional IVF may fail to achieve fertilisation without direct injection.
Why D is wrong: D is not what NCERT names here. ICSI — injecting a single sperm directly into the ovum — is what clinics reach for in severe male-factor infertility, and a student who answers D is thinking about real practice, not making an error. But NCERT assigns low sperm count to AI by name, and NEET keys follow NCERT, which is why the stem asks what NCERT names.
A patient presents with painless ulcer on genitalia (primary stage), followed by skin rashes and mucous membrane lesions. Which pathogen is most likely responsible?
Answer: C. The painless ulcer (chancre) progressing to skin rashes and mucous membrane lesions describes the classic staged presentation of syphilis caused by Treponema pallidum (NCERT Class 12 Biology, Chapter 4).
Why A is wrong: A is wrong — Neisseria gonorrhoeae causes purulent urethral discharge and dysuria, not painless ulcers with staged skin rashes.
Why B is wrong: B is wrong — Chlamydia trachomatis causes urethritis/cervicitis with mucopurulent discharge; does not produce classic chancre.
Why D is wrong: D is wrong — HPV causes genital warts (condylomata acuminata), not painless ulcers progressing through dermatological stages.
In ZIFT, the embryo is transferred into the fallopian tube at which developmental stage?
Answer: B. ZIFT (Zygote Intra-Fallopian Transfer) involves transfer of the zygote or early embryo with up to 8 blastomeres into the fallopian tube. Embryos beyond 8 blastomeres go via IUT into the uterus (NCERT Class 12 Biology, Chapter 4).
Why A is wrong: A is wrong — Morula (16-cell) has >8 blastomeres and would be transferred to the uterus via IUT, not fallopian tube via ZIFT.
Why C is wrong: C is wrong — Blastocyst is a later stage (after morula); transferred via IUT into the uterus for implantation.
Why D is wrong: D is wrong — While a 2-cell stage embryo could technically be part of ZIFT, the answer that encompasses the full correct range is 'up to 8 blastomeres'; D is too restrictive and misleads about the defined cutoff.
A student claims that since hepatitis B is sexually transmitted, it must be a bacterial disease curable with antibiotics. What is the fundamental error in this reasoning?
Answer: A. The error is equating route of transmission with pathogen type. Hepatitis B is caused by HBV (a DNA virus); viral STDs are not curable with antibiotics regardless of transmission route (NCERT Class 12 Biology, Chapter 4).
Why B is wrong: B is wrong — Hepatitis B IS sexually transmitted (also via blood contact, vertical transmission); the route is correct, the pathogen inference is wrong.
Why C is wrong: C is wrong — Hepatitis B is viral (Hepadnavirus), not fungal; this option introduces a different incorrect pathogen category.
Why D is wrong: D is wrong — Antibiotics target bacterial cell machinery; they have no mechanism of action against viral replication. This is never true regardless of timing.
A woman cannot produce ova but her uterine environment is healthy. Her husband has normal semen parameters. An ovum is collected from a donor. Which sequence of ART procedures would be most appropriate?
Answer: C. GIFT is specifically indicated when the female cannot produce ova but can provide conditions for fertilisation and development in her own fallopian tube/uterus. Donor ovum + husband's sperm are placed in the wife's fallopian tube (NCERT Class 12 Biology, Chapter 4). Since the husband's sperm is normal, ICSI is unnecessary.
Why A is wrong: A is wrong — The wife's uterine environment is healthy; transferring to the donor's uterus defeats the purpose and introduces surrogacy unnecessarily.
Why B is wrong: B is wrong — ICSI is specifically for very low sperm count/motility; the husband has normal semen parameters. This adds an unnecessary invasive step.
Why D is wrong: D is wrong — AI of the donor female followed by zygote retrieval is not a standard ART protocol; it conflates AI (which places sperm in a woman for in-vivo fertilisation with her own ovum) with embryo transfer logistics.
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Given
A couple has been trying to conceive for 18 months without success. Investigation reveals: the wife ovulates normally, fallopian tubes are patent, uterine lining is healthy. The husband's semen analysis shows sperm count of 5 million/mL (normal: ≥15 million/mL) with 80% abnormal morphology.
Required
Identify the most appropriate ART and justify why other options are less suitable.
Concept
ART selection depends on identifying the limiting factor. Male factor infertility with severely low sperm count + poor morphology requires direct sperm-ovum intervention rather than relying on natural sperm-ovum interaction.
Relevant facts (not formulas)
• AI requires adequate sperm count for natural fertilisation in the tract.• IVF requires sperm to penetrate the ovum in vitro — still problematic with very low count + abnormal morphology.• ICSI bypasses all sperm motility/morphology barriers by direct injection of a single morphologically-selected sperm into the oocyte.• GIFT/ZIFT require in-vivo or near-in-vivo fertilisation — ineffective with severe male factor.
Analysis
• Wife: normal ovulation, patent tubes, healthy endometrium → female factors are not limiting.• Husband: 5 million/mL (below WHO threshold of 15 million/mL) + 80% abnormal morphology → severe oligoasthenoteratozoospermia (OAT syndrome).• The combination of low count AND poor morphology means even IVF (which requires some sperm to find and penetrate the ovum in a dish) may fail.
Conclusion
ICSI is the most appropriate choice. A single viable sperm is selected by the embryologist (bypassing count and morphology issues) and directly injected into the wife's retrieved oocyte. The resulting embryo can then be transferred to her uterus (she has a healthy uterine environment).
Final answer
ICSI (Intracytoplasmic Sperm Injection) — indicated for severe male factor infertility where sperm count and morphology preclude natural or even standard IVF fertilisation.
Common trap
Confusing ICSI with standard IVF: students assume "test-tube baby" (IVF) covers all infertility. IVF still requires sperm to penetrate the ovum in vitro — with 5 million/mL and 80% abnormal morphology, this is unreliable. ICSI specifically addresses this gap.
Also: confusing GIFT applicability. GIFT is for females who cannot produce ova (anovulatory) but have healthy tubes — it does NOT address male factor.
Similar NEET-style question
"A couple is infertile due to the male partner's azoospermia (zero sperm in ejaculate). Which ART option is NOT possible using the husband's own gametes?"
Answer: None of the standard ARTs work with zero sperm in ejaculate; testicular sperm extraction (TESE) + ICSI or donor sperm would be required.
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STDs: gonorrhoea, syphilis, chlamydia, trichomoniasis, genital herpes, HPV (genital warts), HIV/AIDS. Infertility: 25% male factor, 25% female, 50% combined. ART covers IVF, ZIFT, GIFT.
-- NCERT Class 12 Biology, Ch. 3, p. 47More in Reproduction: 10 exam traps and mistakes · 1 question pattern from its other lessons.
3 questions from NEET 2020, 2023, 2026. Answers verified against NTA official keys.
Which of the following disease is not sexually transmitted ?
Select the option including all sexually transmitted diseases.
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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