Part 4 — Comparison of Mitosis & Meiosis, Chromosomal Abnormalities, Experimental & Applied NEET MCQs (Q76–100)

Q76.

Which process maintains chromosome number in somatic cells across generations?
A. Meiosis
B. Fertilization
C. Mitosis ✅
D. Crossing over

Explanation:

A. Meiosis: Reduces chromosome number.
B. Fertilization: Restores diploidy, not maintenance in somatic cells.
C. Mitosis (Correct): Produces identical diploid daughter cells.
D. Crossing over: Generates variation, not number stability.

Q77.

Which process reduces chromosome number to half?
A. Mitosis
B. Meiosis ✅
C. Cytokinesis
D. DNA replication

Explanation:

**A. Mitosis: chromosome number remains same.
B. Meiosis (Correct): Reduces diploid → haploid.
**C. Cytokinesis: cytoplasmic division only.
**D. DNA replication: doubles DNA, not reduce.

Q78.

Crossing over is unique to:
A. Mitosis
B. Meiosis I ✅
C. Meiosis II
D. Both mitosis & meiosis

Explanation:

**A. Not present in mitosis.
**B. Correct — occurs during prophase I.
**C. Meiosis II: only chromatid separation.
**D. Not both.

Q79.

Which stage of meiosis is most similar to mitosis?
A. Meiosis I
B. Meiosis II ✅
C. Both I & II
D. None

Explanation:

**A. Meiosis I: reductional, very different.
**B. Correct — meiosis II is equational, like mitosis.
**C. Both: incorrect.
**D. At least meiosis II is similar.

Q80.

In humans, how many chromosomes are present at metaphase of mitosis?
A. 23
B. 46 ✅
C. 92
D. 69

Explanation:

**A. 23: haploid, not somatic mitosis.
B. 46 (Correct): Chromosomes duplicated but still 46 units, each with 2 chromatids.
**C. 92: refers to chromatids, not chromosomes.
**D. 69: incorrect.

Q81.

In humans, after meiosis II, how many chromosomes are present in gametes?
A. 23 ✅
B. 46
C. 92
D. 69

Explanation:

**A. Correct — gametes are haploid with 23.
**B. 46: diploid somatic.
**C. 92: chromatid count pre-division.
**D. 69: triploid, abnormal.

Q82.

Which of the following is an example of aneuploidy?
A. Triploidy
B. Monosomy ✅
C. Polyploidy
D. Euploidy

Explanation:

**A. Triploidy: entire set increased (polyploidy).
B. Monosomy (Correct): Loss of a single chromosome, e.g., Turner’s syndrome (45, XO).
**C. Polyploidy: whole set increased.
**D. Euploidy: normal sets.

Q83.

Down syndrome results from:
A. Monosomy of chromosome 21
B. Trisomy of chromosome 21 ✅
C. Triploidy of chromosome 21
D. Duplication of chromosome 22

Explanation:

**A. Monosomy 21: lethal.
B. Trisomy 21 (Correct): Extra chromosome 21 → Down syndrome.
C/D. Incorrect events.

Q84.

Turner’s syndrome is caused by:
A. XXY karyotype
B. XO karyotype ✅
C. XXX karyotype
D. XY karyotype

Explanation:

**A. XXY = Klinefelter’s syndrome.
B. XO (Correct): Only one X chromosome → Turner’s syndrome.
**C. XXX = Triple X.
**D. XY = normal male.

Q85.

Failure of homologous chromosomes to separate is termed:
A. Crossing over
B. Non-disjunction ✅
C. Synapsis
D. Terminalization

Explanation:

**A. Crossing over: recombination.
B. Non-disjunction (Correct): Failure of homologues (meiosis I) or chromatids (meiosis II) to segregate.
**C. Synapsis: pairing.
**D. Terminalization: movement of chiasmata.

Q86.

Klinefelter’s syndrome individuals have:
A. 45, XO
B. 47, XXY ✅
C. 47, XXX
D. 46, XY

Explanation:

**A. XO = Turner’s.
B. XXY (Correct): Klinefelter’s syndrome, male with extra X.
**C. XXX = Triple X female.
**D. Normal male.

Q87.

Polyploidy is more common in:
A. Animals
B. Plants ✅
C. Bacteria
D. Fungi

Explanation:

**A. Rare and often lethal in animals.
**B. Correct — many crops (wheat, potato) are polyploids.
**C. Bacteria = haploid, not polyploid.
**D. Fungi: some polyploid forms exist, but less common.

Q88.

Which process is used to prepare karyotypes in cytogenetics labs?
A. Arresting cells in S phase
B. Arresting cells in metaphase ✅
C. Arresting cells in anaphase
D. Arresting cells in G0

Explanation:

**A. S phase: chromosomes not condensed.
**B. Correct — metaphase chromosomes are condensed, ideal for karyotyping.
**C. Anaphase: separating, not ideal.
**D. G0: non-dividing, unsuitable.

Q89.

Which chemical arrests cells in metaphase for karyotyping?
A. Colchicine ✅
B. Penicillin
C. Streptomycin
D. Taxol

Explanation:

A. Colchicine (Correct): Prevents spindle formation → metaphase arrest.
B/C. Antibiotics, not spindle blockers.
**D. Taxol stabilizes microtubules, not metaphase arresting agent.

Q90.

Which abnormality is NOT due to non-disjunction?
A. Down syndrome
B. Turner’s syndrome
C. Klinefelter’s syndrome
D. Huntington’s disease ✅

Explanation:

A–C: All aneuploidies from non-disjunction.
**D. Huntington’s: trinucleotide repeat mutation, not segregation error.

Q91.

In meiosis, the chromosomes that fail to separate produce gametes with abnormal numbers. Fertilization of such gametes leads to:
A. Aneuploid zygote ✅
B. Normal zygote
C. Haploid zygote
D. Euploid zygote

Explanation:

**A. Correct — abnormal chromosome numbers → aneuploidy.
**B. Not possible if gametes abnormal.
C/D. Haploid/euploid only with normal gametes.

Q92.

In which of the following cases is mitosis preferred over meiosis?
A. Production of gametes
B. Growth and repair ✅
C. Formation of genetic diversity
D. Reduction in chromosome number

Explanation:

**A. Gametes: meiosis.
**B. Correct — mitosis makes identical cells for growth/repair.
C/D. Meiosis-specific.

Q93.

Which of the following events is unique to meiosis?
A. Synapsis ✅
B. Chromatid separation
C. Spindle formation
D. Cytokinesis

Explanation:

A. Synapsis (Correct): Homolog pairing unique to meiosis.
B–D. Common to both mitosis and meiosis.

Q94.

Which type of error causes trisomy conditions?
A. Gene mutation
B. Chromosomal non-disjunction ✅
C. Transcription error
D. Translation error

Explanation:

**A. Gene mutation: base-level, not whole chromosome.
**B. Correct — failure of chromosomes to segregate → trisomy.
C/D. RNA/protein-level errors.

Q95.

Experimental evidence for “cell cycle regulation by cytoplasmic factors” came from:
A. Meselson-Stahl experiment
B. Cell fusion experiments ✅
C. Avery–McLeod experiment
D. Griffith’s experiment

Explanation:

**A. Meselson-Stahl: DNA replication.
**B. Correct — fusing cells in different stages showed cytoplasm controls progression.
C/D. DNA as genetic material experiments.

Q96.

During meiosis, non-disjunction of sex chromosomes may result in:
A. XO (Turner’s syndrome) ✅
B. Down syndrome
C. Huntington’s disease
D. Sickle-cell anemia

Explanation:

A. XO (Correct): Missing sex chromosome from non-disjunction.
**B. Down: autosomal, not sex.
C/D. Gene-level disorders.

Q97.

Which statement is true for mitosis but not for meiosis?
A. Maintains genetic stability ✅
B. Produces variation
C. Reductional division
D. Occurs in germ cells

Explanation:

**A. Correct — mitosis conserves genome.
**B. Variation: meiosis.
**C. Reduction: meiosis I.
**D. Germ cells undergo meiosis.

Q98.

A diploid cell has 12 chromosomes. After meiosis I, each daughter cell will have:
A. 6 chromosomes ✅
B. 12 chromosomes
C. 24 chromosomes
D. 3 chromosomes

Explanation:

**A. Correct — reduction division halves number (12 → 6).
**B. 12: mitosis.
C/D. Not valid.

Q99.

Chromosomal non-disjunction most commonly occurs during:
A. Metaphase alignment
B. Anaphase separation ✅
C. Prophase condensation
D. Telophase

Explanation:

**A. Orientation errors may predispose but not actual nondisjunction.
**B. Correct — homologues or chromatids fail to separate in anaphase.
C/D. Not relevant.

Q100.

The clinical technique “amniocentesis” is used to detect:
A. Gene mutations only
B. Chromosomal abnormalities like Down syndrome ✅
C. Protein structure defects
D. Cytoplasmic inheritance

Explanation:

**A. Point mutations not easily detected by amniocentesis.
**B. Correct — fetal karyotyping to detect aneuploidies like trisomy 21.
**C. Protein structure not assessed.
**D. Cytoplasmic inheritance not analyzed.

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Part 4 — Comparison of Mitosis & Meiosis, Chromosomal Abnormalities, Experimental & Applied NEET MCQs (Q76–100)