Questions & explanations
1. Which of the following is a significance of meiosis?
- Maintains constant chromosome number across generations
- Produces genetically identical cells
- Increases chromosome number in offspring
- Reduces genetic variation
Answer: Maintains constant chromosome number across generations
Meiosis reduces the chromosome number by half, ensuring that when gametes fuse during fertilization, the diploid number is restored, maintaining chromosome number across generations. It also generates genetic variation through crossing over and independent assortment.
2. In meiosis, the reduction in chromosome number occurs during:
- Meiosis I only
- Meiosis II only
- Both meiosis I and II
- Neither meiosis I nor II
Answer: Meiosis I only
Meiosis I is the reductional division where homologous chromosomes separate, reducing the chromosome number from diploid to haploid. Meiosis II is equational, similar to mitosis, separating sister chromatids without further reduction.
3. During anaphase I of meiosis, which structures separate?
- Sister chromatids
- Homologous chromosomes
- Non-homologous chromosomes
- Centrioles
Answer: Homologous chromosomes
In anaphase I, homologous chromosomes are pulled apart by spindle fibers and move to opposite poles, reducing the chromosome number. Sister chromatids remain attached.
4. Meiosis II is most similar to which process?
- Mitosis
- Meiosis I
- Cytokinesis
- DNA replication
Answer: Mitosis
Meiosis II is equational, like mitosis, where sister chromatids separate, resulting in four haploid cells. It does not involve further reduction in chromosome number.
5. The structure that holds homologous chromosomes together during synapsis is called:
- Chiasmata
- Synaptonemal complex
- Centromere
- Spindle fibers
Answer: Synaptonemal complex
The synaptonemal complex is a protein structure that forms between homologous chromosomes during synapsis in zygotene, facilitating pairing and recombination.
6. During which stage of prophase I does crossing over occur?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
Answer: Pachytene
Crossing over, the exchange of genetic material between non-sister chromatids of homologous chromosomes, occurs during the pachytene stage of prophase I.
7. Mitosis is often referred to as equational division because:
- The chromosome number is halved
- The daughter cells have the same number of chromosomes as the parent cell
- The daughter cells are genetically different from the parent cell
- The division results in four daughter cells
Answer: The daughter cells have the same number of chromosomes as the parent cell
Mitosis produces two daughter cells with identical chromosome number and genetic content as the parent cell, hence it is called equational division.
8. Which of the following is a significance of mitosis?
- Production of gametes
- Growth and repair of tissues
- Introduction of genetic variation
- Reduction of chromosome number
Answer: Growth and repair of tissues
Mitosis is responsible for growth, repair, and maintenance of chromosome number; it does not produce gametes or introduce variation.
9. Cytokinesis in plant cells differs from animal cells because plant cells form:
- A cleavage furrow
- A cell plate
- A contractile ring
- A spindle apparatus
Answer: A cell plate
Plant cells form a cell plate from Golgi vesicles that develops into a new cell wall, whereas animal cells form a cleavage furrow.
10. Which of the following best describes the outcome of meiosis?
- Two diploid cells from one diploid cell
- Four haploid cells from one diploid cell
- Two haploid cells from one diploid cell
- Four diploid cells from one haploid cell
Answer: Four haploid cells from one diploid cell
Meiosis is a reductional division that reduces the chromosome number by half, producing four haploid cells from one diploid cell.
11. In metaphase of mitosis, chromosomes:
- Move to opposite poles
- Decondense into chromatin
- Align at the equatorial plate
- Replicate their DNA
Answer: Align at the equatorial plate
During metaphase, chromosomes line up at the metaphase plate (equatorial plate) with kinetochores attached to spindle fibers.