Meiosis – stages and genetic significance MCQs With Answer is a concise, focused review tailored for B. Pharm students studying cell division, reductional division, and heredity. This introduction covers key concepts: meiosis stages (Prophase I substages, Metaphase I, Anaphase I, Telophase I, Meiosis II), crossing‑over, homologous recombination, independent assortment, and outcomes such as gametogenesis and genetic variation. Understanding chromosomal segregation, nondisjunction, and molecular players helps pharmacists appreciate implications for congenital disorders, drug effects on germ cells, and principles behind genetic counseling. Clear, factual questions reinforce learning and exam readiness. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which event distinguishes meiosis I from meiosis II?
- Separation of sister chromatids
- DNA replication during S phase
- Separation of homologous chromosomes
- Formation of spindle fibers
Correct Answer: Separation of homologous chromosomes
Q2. During which substage of Prophase I does crossing-over primarily occur?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
Correct Answer: Pachytene
Q3. What structure physically indicates sites of genetic recombination between homologs?
- Centromere
- Chiasma (chiasmata)
- Kinetochore
- Telomere
Correct Answer: Chiasma (chiasmata)
Q4. Which protein or enzyme is primarily responsible for initiating double-strand breaks that lead to meiotic recombination in many organisms?
- Topoisomerase II
- Spo11
- RecA
- DNA ligase
Correct Answer: Spo11
Q5. Independent assortment of chromosomes occurs during which meiotic stage?
- Prophase I
- Metaphase I
- Anaphase II
- Telophase II
Correct Answer: Metaphase I
Q6. What is the ploidy of cells at the end of meiosis I in a diploid organism?
- Diploid (2n)
- Haploid (n) but chromosomes still consist of two chromatids
- Haploid (n) with single chromatids
- Tetraploid (4n)
Correct Answer: Haploid (n) but chromosomes still consist of two chromatids
Q7. Which process increases genetic diversity by creating new allele combinations within chromosomes?
- Independent assortment
- Crossing‑over (recombination)
- Nondisjunction
- Mitosis
Correct Answer: Crossing‑over (recombination)
Q8. Nondisjunction during meiosis can lead to which outcome in offspring?
- Point mutation
- Aneuploidy such as trisomy or monosomy
- Inversion of chromosome segments
- Translocation without phenotypic effect
Correct Answer: Aneuploidy such as trisomy or monosomy
Q9. Which statement correctly contrasts spermatogenesis and oogenesis?
- Both produce four functional gametes per meiotic cycle
- Spermatogenesis yields four sperm; oogenesis yields one ovum and polar bodies
- Oogenesis is continuous throughout life with no arrest stages
- Spermatogenesis includes prolonged arrest in prophase I
Correct Answer: Spermatogenesis yields four sperm; oogenesis yields one ovum and polar bodies
Q10. Which checkpoint or mechanism helps protect sister chromatid cohesion until anaphase II?
- p53-mediated DNA damage response
- Shugoshin protecting centromeric cohesin
- Spindle assembly checkpoint only in mitosis
- Telomerase activation
Correct Answer: Shugoshin protecting centromeric cohesin
Q11. What is the significance of the synaptonemal complex in meiosis?
- It degrades cohesin proteins
- It facilitates pairing and recombination of homologous chromosomes
- It separates sister chromatids at anaphase II
- It replicates DNA prior to meiosis
Correct Answer: It facilitates pairing and recombination of homologous chromosomes
Q12. In a human cell, if nondisjunction occurs during Meiosis I for chromosome 21, what is the expected result in gametes?
- All gametes will be normal
- Two gametes with n+1 and two with n-1
- One gamete with n+2 and three normal
- All gametes will lack chromosome 21
Correct Answer: Two gametes with n+1 and two with n-1
Q13. Which substage of Prophase I is characterized by visible separation of homologs while chiasmata remain?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
Correct Answer: Diplotene
Q14. Which event must occur before a cell can enter meiosis I?
- DNA replication during S phase
- Separation of sister chromatids
- Fusion of gametes
- Completion of cytokinesis
Correct Answer: DNA replication during S phase
Q15. How does crossing‑over contribute to genetic mapping in humans?
- By creating new mutations that define gene order
- By providing recombination frequencies proportional to physical distance between genes
- By preventing linkage between all loci
- By eliminating allelic variation
Correct Answer: By providing recombination frequencies proportional to physical distance between genes
Q16. Which of the following best describes chiasma frequency between two loci?
- Directly equals number of base pairs between loci
- Is unrelated to recombination frequency
- Reflects historical crossover events and correlates with recombination rate
- Is fixed for all organisms
Correct Answer: Reflects historical crossover events and correlates with recombination rate
Q17. Which result would indicate reductional division has occurred?
- Chromosome number remains 2n after division
- Chromosome number is halved from diploid to haploid
- Sister chromatids separate while homologs remain together
- DNA content doubles
Correct Answer: Chromosome number is halved from diploid to haploid
Q18. A drug that interferes with microtubule polymerization would most directly block which meiotic step?
- Homolog pairing in Prophase I
- Crossing‑over during Pachytene
- Chromosome alignment and segregation during metaphase/anaphase
- DNA replication before meiosis
Correct Answer: Chromosome alignment and segregation during metaphase/anaphase
Q19. Which is true about meiosis-derived gametes compared to the original germ cell?
- They are genetically identical to each other
- They are haploid and genetically distinct due to recombination and assortment
- They have double the DNA content
- They retain homologous chromosome pairs
Correct Answer: They are haploid and genetically distinct due to recombination and assortment
Q20. What is the likely consequence if cohesin is degraded prematurely during meiosis I?
- Enhanced crossing‑over fidelity
- Premature separation of sister chromatids leading to aneuploidy
- Failure of homolog pairing
- No effect on chromosome segregation
Correct Answer: Premature separation of sister chromatids leading to aneuploidy
Q21. Which term describes two homologous chromosomes physically paired during Prophase I?
- Tetrad or bivalent
- Dyad
- Univalent
- Chromatid
Correct Answer: Tetrad or bivalent
Q22. Which meiotic abnormality is most commonly associated with maternal age effect in humans?
- Point mutations in sperm DNA
- Nondisjunction leading to conditions like Down syndrome
- Translocations during spermatogenesis
- Increased telomere length in oocytes
Correct Answer: Nondisjunction leading to conditions like Down syndrome
Q23. Which statement best explains linkage between two genes?
- Genes on different chromosomes are always linked
- Genes close together on the same chromosome tend to be inherited together due to reduced recombination between them
- Linked genes cannot undergo crossing‑over
- Linkage refers to genes with identical DNA sequences
Correct Answer: Genes close together on the same chromosome tend to be inherited together due to reduced recombination between them
Q24. During which meiotic stage do homologous chromosomes reach opposite poles and the cell becomes haploid?
- Metaphase I
- Anaphase I
- Anaphase II
- Telophase II
Correct Answer: Anaphase I
Q25. Which experimental observation would indicate crossing‑over occurred between two marker loci?
- Offspring display only parental phenotypes
- Offspring include recombinant phenotypes not seen in either parent
- No variation observed among progeny
- All progeny are genetically identical to one parent
Correct Answer: Offspring include recombinant phenotypes not seen in either parent
Q26. Which is TRUE about homologous recombination during meiosis?
- It always results in gene conversion without exchange
- It can produce crossovers and noncrossovers, altering allele combinations
- It requires mitotic spindle formation
- It prevents formation of chiasmata
Correct Answer: It can produce crossovers and noncrossovers, altering allele combinations
Q27. Which of the following best describes a polar body produced in oogenesis?
- A functional gamete destined to fertilize
- A small haploid cell that typically degenerates
- A diploid precursor cell
- An accessory cell forming the placenta
Correct Answer: A small haploid cell that typically degenerates
Q28. In genetic counseling, why is understanding meiotic nondisjunction important for pharmacists?
- It determines drug absorption rates
- It underlies congenital aneuploidies that affect medication dosing and safety
- It directly alters drug metabolism enzymes in adults
- It predicts patient adherence to therapy
Correct Answer: It underlies congenital aneuploidies that affect medication dosing and safety
Q29. Which observation distinguishes metaphase I from metaphase II microscopically?
- Homologous pairs lined up at the metaphase plate in metaphase I; single chromosomes in metaphase II
- DNA replication occurs in metaphase II only
- Sister chromatids are already separated in metaphase I
- Spindle fibers are absent in metaphase I
Correct Answer: Homologous pairs lined up at the metaphase plate in metaphase I; single chromosomes in metaphase II
Q30. Which molecular consequence of recombination can affect drug response across individuals?
- Recombination eliminates all polymorphisms in drug metabolizing genes
- Recombination can create new combinations of alleles for pharmacogenes, altering drug metabolism and efficacy
- Recombination only affects noncoding DNA with no clinical consequence
- Recombination causes immediate dominant drug resistance in somatic cells
Correct Answer: Recombination can create new combinations of alleles for pharmacogenes, altering drug metabolism and efficacy
