The high-frequency trap in mitosis questions: confusing mitosis-specific events with meiosis-specific ones. Synapsis, crossing over, and chiasmata formation belong exclusively to prophase I of meiosis. Mitosis is equational — no pairing of homologues occurs at any stage.
The four phases of mitosis:
Prophase: Chromatin condenses into distinct chromosomes (each consisting of two sister chromatids joined at the centromere). The nucleolus disappears. The mitotic spindle begins to form from centrosomes moving to opposite poles. The nuclear envelope remains intact through most of prophase but breaks down at late prophase/prometaphase.
Metaphase: Chromosomes align at the metaphase plate (cell equator). Spindle fibres from opposite poles attach to kinetochores on sister chromatids. This alignment ensures each daughter cell receives one chromatid from every chromosome. The cell's chromosomes are most condensed and visible here — karyotyping is done at metaphase.
Anaphase: Centromeres split. Sister chromatids separate and move to opposite poles, pulled by shortening spindle fibres. Once separated, each chromatid is now an independent chromosome. This is the shortest phase of mitosis.
Telophase: Chromosomes reach the poles and decondense. Nuclear envelopes reform around each set. Nucleoli reappear. The spindle disassembles. Cytokinesis (cytoplasmic division) typically overlaps with telophase.
Critical distinction for NEET: In mitosis, sister chromatids separate at anaphase. In meiosis I, homologous chromosomes separate at anaphase I; sister chromatids separate only at anaphase II. Confusing these two separation events is a common source of negative marks.
NCERT Class 11 Biology Chapter 10, page 122 provides the reference framework for mitotic stages.
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 events occurs during prophase of mitosis?
Answer: C. Chromatin condensation into visible chromosomes is the hallmark event of prophase (NCERT Class 11 Biology Chapter 10, page 129).
Why A is wrong: A is wrong because separation of sister chromatids occurs at anaphase, not prophase (trap: confusing phase-specific events).
Why B is wrong: B is wrong because chromosome alignment at the metaphase plate is the defining feature of metaphase.
Why D is wrong: D is wrong because reformation of the nuclear envelope occurs during telophase, when chromosomes have already reached the poles.
Karyotyping is best performed during which stage of mitosis?
Answer: B. At metaphase, chromosomes are maximally condensed and aligned at the equator, making them most clearly visible for karyotype analysis (NCERT Class 11 Biology Chapter 10).
Why A is wrong: A is wrong because during prophase chromosomes are still condensing and are not yet at maximum compaction — morphological detail is less clear.
Why C is wrong: C is wrong because at anaphase chromosomes are moving rapidly toward poles, making morphological assessment unreliable.
Why D is wrong: D is wrong because during telophase chromosomes begin to decondense and are progressively less distinct.
Which is the shortest phase of mitosis?
Answer: A. Anaphase is the shortest phase of mitosis — it involves only the splitting of centromeres and the poleward movement of chromatids (NCERT Class 11 Biology Chapter 10).
Why B is wrong: B is wrong because metaphase, while shorter than prophase, is not the shortest — the spindle assembly checkpoint ensures proper kinetochore attachment before proceeding.
Why C is wrong: C is wrong because prophase is typically the longest phase of mitosis, involving multiple preparatory events (condensation, spindle formation, nuclear envelope breakdown).
Why D is wrong: D is wrong because telophase involves multiple events (decondensation, nuclear envelope reformation, nucleolus reappearance) and overlaps with cytokinesis, taking longer than anaphase.
During anaphase of mitosis, what separates and moves to opposite poles?
Answer: D. In mitotic anaphase, centromeres split and sister chromatids (now individual chromosomes) move to opposite poles. Homologue separation is a meiosis I event (trap: mitosis vs meiosis stage characteristics).
Why A is wrong: A is wrong because homologous chromosome separation occurs at anaphase I of meiosis, not mitotic anaphase (trap: confusing mitosis with meiosis I).
Why B is wrong: B is wrong because bivalents (homologous pairs held by chiasmata) are meiosis-specific structures that separate at anaphase I.
Why C is wrong: C is wrong because tetrads (groups of four chromatids from a homologous pair) form only during meiosis I prophase — they do not exist in mitosis.
A student observes a cell where the nuclear envelope has reformed, chromosomes are decondensing, and a nucleolus is reappearing. The cell is in:
Answer: C. Reformation of the nuclear envelope, chromosome decondensation, and nucleolus reappearance are the three hallmark events of telophase — essentially the reverse of prophase (NCERT Class 11 Biology Chapter 10).
Why A is wrong: A is wrong because late prophase is characterized by nuclear envelope breakdown and chromosome condensation — the opposite of what is described.
Why B is wrong: B is wrong because during metaphase the nuclear envelope is absent and chromosomes are maximally condensed at the equator.
Why D is wrong: D is wrong because during anaphase chromatids are moving to poles; no reformation events occur yet.
Which of the following is TRUE about mitosis?
Answer: D. Mitosis is equational division — it produces two daughter cells genetically identical to the parent. Synapsis, crossing over, and homologue pairing are meiosis-exclusive events (trap: mitosis vs meiosis stage characteristics swapped).
Why A is wrong: A is wrong because synapsis (pairing of homologous chromosomes) occurs only in prophase I of meiosis, never in mitosis (trap: attributing meiosis-specific events to mitosis).
Why B is wrong: B is wrong because crossing over occurs between non-sister chromatids of homologous chromosomes during meiosis I prophase — it does not occur in mitosis.
Why C is wrong: C is wrong because in mitosis, individual chromosomes (not homologous pairs) align independently at the metaphase plate.
A diploid organism has 2n = 6 chromosomes. A cell of this organism is examined at metaphase of mitosis. DNA replication in the preceding S phase does not change chromosome number, and each chromosome at metaphase consists of two sister chromatids joined at the centromere. How many sister chromatids are present in total in this cell?
Answer: C. Chromosome number is conserved through S-phase replication, so the cell still has 2n = 6 chromosomes at metaphase; since each chromosome is made up of two sister chromatids held together at the centromere, the total chromatid count is 6 × 2 = 12 (NCERT Class 11 Biology, Chapter 10, page 123).
Why A is wrong: A is wrong because 3 results from halving the chromosome number, confusing DNA replication (which conserves chromosome number) with meiotic reduction division.
Why B is wrong: B is wrong because 6 counts only the chromosomes (2n) and ignores that each chromosome at metaphase is made of two sister chromatids.
Why D is wrong: D is wrong because 24 assumes four chromatids per chromosome, which describes a meiotic tetrad/bivalent structure, not a mitotic chromosome.
A student claims: "In mitotic anaphase, homologous chromosomes separate, reducing the chromosome number by half." What is the error?
Answer: B. The fundamental error is that mitotic anaphase separates sister chromatids (not homologues). Homologue separation is an anaphase I (meiosis) event. Mitosis does not halve chromosome number (trap: sister chromatids vs homologues confusion).
Why A is wrong: A is wrong because homologous chromosomes do NOT separate in mitosis at all — they move independently. This option retains the core misconception.
Why C is wrong: C is wrong on two counts: chromosome number is not halved in mitosis, and no separation event occurs at metaphase (metaphase is alignment, not separation).
Why D is wrong: D is wrong because mitosis never halves chromosome number regardless of cell type. Even in reproductive tissues, meiosis (not mitosis) achieves reduction.
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Given
Four cellular events. Task: identify those exclusive to mitosis (not shared with meiosis I).
Required
The correct combination of mitosis-exclusive events.
Concept
Mitosis is equational. It lacks synapsis, crossing over, and chiasmata. Sister chromatid separation occurs at anaphase of mitosis (and anaphase II of meiosis, but NOT anaphase I). Individual chromosome alignment at the equator occurs in mitosis; in meiosis I, bivalents (homologous pairs) align instead.
Formula/Rule
No mathematical formula. The rule: Synapsis + crossing over = meiosis I exclusive. Sister chromatid separation + individual alignment = mitosis features.
Substitution/Application
• (i) Synapsis → meiosis I only. NOT mitosis. Exclude.• (ii) Sister chromatid separation at anaphase → mitosis (and meiosis II). Occurs in mitosis. Include.• (iii) Crossing over → meiosis I only. NOT mitosis. Exclude.• (iv) Individual chromosome alignment → mitosis. In meiosis I, bivalents align, not individual chromosomes. Include.
Calculation
No arithmetic. Logical filtering: events (ii) and (iv) occur in mitosis but not in meiosis I.
Final answer
(B) (ii) and (iv) only.
Common trap
Selecting option (C) by mistakenly including synapsis as a mitosis event. Synapsis is the hallmark of meiosis I prophase — homologous chromosomes pair side by side. This never occurs in mitosis.
Similar NEET-style question
"Which of the following events does NOT occur during mitosis?
(A) Disappearance of nucleolus (B) Splitting of centromere (C) Formation of chiasmata (D) Cytokinesis"
Answer: (C) — Chiasmata form only during meiosis I as a result of crossing over.
---
Equational division — 2n → 2n. Prophase: chromosomes condense, spindle forms. Metaphase: chromosomes at equator. Anaphase: sister chromatids separate. Telophase: nuclei reform. Cytokinesis: cleavage furrow (animal) / cell plate (plant).
-- NCERT Class 11 Biology, Ch. 10, p. 122These are the exact patterns that cause wrong answers in NEET. Each trap includes when it triggers and how to avoid it.
Category: Similar Terms
Synapsis, crossing over, chiasmata are meiosis-only (prophase I). Equational mitosis has none.
Question describes a phase event and asks which division it belongs to.
Synapsis/CO/chiasmata = meiosis I. Sister chromatid separation = mitosis or meiosis II. Homologue separation = meiosis I.
Root cause: term confusion
Sister chromatids = two copies after S phase, joined at centromere. Homologues = paired chromosomes (one maternal, one paternal). Anaphase I separates homologues; Anaphase II separates sisters.
More in Cell: Structure and Function: 12 exam traps and mistakes · 1 formula · 1 question pattern from its other lessons.
4 questions from NEET 2022, 2024, 2025. Answers verified against NTA official keys.
What is the main function of the spindle fibers during mitosis?
Spindle fibers attach to kinetochores of chromosomes during
Which one of the following never occurs during mitotic cell division?
Select the incorrect statement with reference to mitosis:
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