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10. Meiosis and Genetic Diversity — Practice Questions 2
This chapter examines how meiosis reduces chromosome number, introduces genetic variation through crossing-over and independent assortment, and how errors like nondisjunction lead to chromosomal abnormalities.
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(Multiple Choice — Click to Reveal Answer)
1. Which best describes the chromosome number in cells produced by meiosis?
(A) Same as the parent cell
(B) Double the parent cell
(C) Half the parent cell
(D) Varies depending on organism
Answer
(C) — Meiosis reduces the chromosome number by half, creating haploid cells.
2. What is a major difference between meiosis I and meiosis II?
(A) Meiosis I separates chromatids
(B) Meiosis II separates homologous chromosomes
(C) DNA replicates between them
(D) Meiosis I separates homologous chromosomes
Answer
(D) — Meiosis I separates homologous chromosomes, while meiosis II separates sister chromatids.
3. Which term refers to the physical exchange of chromosome segments between non-sister chromatids?
(A) Independent assortment
(B) Mutation
(C) Crossing-over
(D) Synapsis
Answer
(C) — Crossing-over creates genetic diversity by exchanging DNA between non-sister chromatids.
4. During which stage of meiosis do tetrads form?
(A) Metaphase I
(B) Prophase I
(C) Anaphase II
(D) Telophase I
Answer
(B) — Tetrads form when homologous chromosomes pair during prophase I.
5. How many chromatids are in a human cell at the start of meiosis I?
(A) 23
(B) 46
(C) 92
(D) 184
Answer
(C) — There are 46 chromosomes, each with two sister chromatids, totaling 92 chromatids.
6. Which of the following occurs in meiosis but not in mitosis?
(A) Cytokinesis
(B) Spindle formation
(C) Homologous chromosome pairing
(D) Chromatid separation
Answer
(C) — Only meiosis involves pairing of homologous chromosomes during prophase I.
7. If an organism has a diploid number of 12, how many chromosomes are in each gamete?
(A) 3
(B) 6
(C) 12
(D) 24
Answer
(B) — Meiosis produces gametes with half the diploid number: 6 in this case.
8. What is the role of meiosis in sexual reproduction?
(A) Produces identical daughter cells
(B) Reduces chromosome number and introduces variation
(C) Repairs damaged DNA
(D) Duplicates the genome for growth
Answer
(B) — Meiosis ensures gametes have half the chromosome number and promotes genetic variation.
9. In which phase do sister chromatids separate during meiosis?
(A) Anaphase I
(B) Anaphase II
(C) Telophase I
(D) Metaphase II
Answer
(B) — Sister chromatids separate during anaphase II.
10. What type of cell division is responsible for genetic recombination?
(A) Meiosis
(B) Binary fission
(C) Mitosis
(D) Budding
Answer
(A) — Meiosis, specifically in prophase I, allows for recombination through crossing-over.
11. Which of the following stages occurs directly after telophase I?
(A) Prophase I
(B) Cytokinesis I
(C) Metaphase II
(D) Interphase II
Answer
(C) — After telophase I and cytokinesis, meiosis II begins with prophase II followed by metaphase II.
12. What is the term for the side-by-side alignment of homologous chromosomes during prophase I?
(A) Crossing-over
(B) Synapsis
(C) Assortment
(D) Replication
Answer
(B) — Synapsis refers to the pairing of homologous chromosomes to form tetrads.
13. What is the ploidy of the cells at the end of meiosis I?
(A) Diploid with duplicated chromosomes
(B) Diploid with unduplicated chromosomes
(C) Haploid with duplicated chromosomes
(D) Haploid with unduplicated chromosomes
Answer
(C) — At the end of meiosis I, cells are haploid, but their chromosomes still consist of sister chromatids.
14. What is the function of the spindle apparatus in meiosis?
(A) To synthesize chromosomes
(B) To separate chromosomes
(C) To replicate DNA
(D) To repair mutations
Answer
(B) — The spindle apparatus pulls chromosomes or chromatids to opposite poles of the cell.
15. Which of the following increases genetic diversity during meiosis?
(A) Cytokinesis
(B) Chromatin condensation
(C) Independent assortment
(D) Spindle formation
Answer
(C) — Independent assortment during metaphase I leads to different chromosome combinations in gametes.
16. Which term refers to the failure of homologous chromosomes or sister chromatids to separate properly?
(A) Translocation
(B) Inversion
(C) Nondisjunction
(D) Duplication
Answer
(C) — Nondisjunction leads to an abnormal number of chromosomes in daughter cells.
17. Which of the following statements is true about meiosis but not mitosis?
(A) It results in identical cells
(B) It involves two nuclear divisions
(C) It occurs in somatic cells
(D) It increases chromosome number
Answer
(B) — Meiosis includes two rounds of nuclear division, reducing chromosome number.
18. What term describes one version of a gene located on a chromosome?
(A) Locus
(B) Allele
(C) Tetrad
(D) Codon
Answer
(B) — An allele is a version of a gene found at a specific locus on a chromosome.
19. What is the product of meiosis in male animals?
(A) Two gametes
(B) Four sperm cells
(C) One functional gamete
(D) Eight daughter cells
Answer
(B) — Meiosis in males results in four functional sperm cells.
20. When does the nuclear envelope reform in meiosis II?
(A) Prophase I
(B) Telophase II
(C) Anaphase I
(D) Metaphase II
Answer
(B) — Nuclear envelopes reform during telophase II, completing the meiotic process.
21. What does each chromosome consist of after DNA replication and before meiosis I begins?
(A) One chromatid
(B) Two non-homologous chromatids
(C) Two sister chromatids
(D) Four chromatids
Answer
(C) — After replication, each chromosome has two identical sister chromatids.
22. Which of the following does NOT occur during meiosis I?
(A) Synapsis
(B) Crossing-over
(C) Separation of homologous chromosomes
(D) Separation of sister chromatids
Answer
(D) — Sister chromatids separate during meiosis II, not meiosis I.
23. What causes a zygote to have a trisomy condition such as Down syndrome?
(A) Crossing-over
(B) Polyploidy
(C) Nondisjunction during meiosis
(D) Independent assortment
Answer
(C) — Nondisjunction leads to an abnormal number of chromosomes in gametes, such as trisomy 21.
24. What structure is formed by synapsis of homologous chromosomes?
(A) Chromatid
(B) Chromosome
(C) Tetrad
(D) Centrosome
Answer
(C) — A tetrad forms during prophase I when homologous chromosomes pair up.
25. How does sexual reproduction differ from asexual reproduction in terms of genetic outcomes?
(A) Offspring are genetically identical in both
(B) Sexual reproduction increases variation
(C) Asexual reproduction creates gametes
(D) Sexual reproduction creates diploid spores
Answer
(B) — Sexual reproduction leads to genetically varied offspring due to meiosis and fertilization.
26. What is the significance of chiasmata during meiosis?
(A) They prevent crossing-over
(B) They indicate where sister chromatids attach
(C) They are the sites where non-sister chromatids exchange DNA
(D) They hold together spindle fibers
Answer
(C) — Chiasmata are physical sites where crossing-over occurs between homologous chromosomes during prophase I.
27. What would likely occur if synapsis failed during meiosis?
(A) Crossing-over would increase
(B) Homologous chromosomes would not pair, preventing tetrad formation
(C) Sister chromatids would separate too early
(D) Mitosis would begin
Answer
(B) — Without synapsis, homologs wouldn’t pair or undergo crossing-over, disrupting meiosis I.
28. A gene is located near the centromere. How would this affect recombination frequency?
(A) It would increase dramatically
(B) It would remain constant
(C) It would be lower than genes near chromosome ends
(D) It would not affect recombination
Answer
(C) — Recombination is less likely near centromeres due to tight chromatin packing.
29. In organisms with a 2n = 16, how many chromosome combinations are possible in gametes just from independent assortment?
(A) 8
(B) 16
(C) 128
(D) 256
Answer
(D) — Independent assortment allows for 2ⁿ combinations; 2⁸ = 256.
30. Which of the following errors during meiosis could result in a zygote with monosomy?
(A) Early crossing-over
(B) Delayed cytokinesis
(C) Nondisjunction in either meiosis I or II
(D) Telophase II skipping
Answer
(C) — Nondisjunction causes gametes to have missing or extra chromosomes, leading to monosomy or trisomy.
31. What is a major difference in the way male and female animals complete meiosis?
(A) Females produce four equal gametes; males produce one
(B) Males stop at prophase I; females do not
(C) Males produce four sperm; females produce one ovum and polar bodies
(D) Females undergo mitosis instead of meiosis
Answer
(C) — Oogenesis results in one functional ovum and three polar bodies, while spermatogenesis produces four sperm.
32. Which mechanism explains why linked genes may be inherited together?
(A) They are transcribed together
(B) They are on different chromosomes
(C) They are located far apart
(D) They are physically close on the same chromosome
Answer
(D) — Genes that are close together on the same chromosome are less likely to be separated by crossing-over.
33. A nondisjunction event occurs during meiosis II in a female. How many of the resulting gametes are expected to be abnormal?
(A) All 4
(B) 1
(C) 2
(D) None
Answer
(C) — If nondisjunction occurs in one meiosis II division, 2 out of 4 gametes are abnormal.
34. What is the functional significance of polar bodies in female meiosis?
(A) They store extra chromosomes
(B) They ensure that most cytoplasm remains in the ovum
(C) They become additional gametes
(D) They aid in recombination
Answer
(B) — Polar bodies allow the oocyte to retain most cytoplasm, which supports embryo development if fertilized.
35. Which genetic concept is supported by the random orientation of chromosomes in metaphase I?
(A) Law of dominance
(B) Law of segregation
(C) Law of independent assortment
(D) Central dogma of biology
Answer
(C) — The law of independent assortment is demonstrated by the random alignment of homologs in metaphase I.
36. Explain how independent assortment contributes to genetic variation.
Answer
Independent assortment occurs during metaphase I when homologous chromosomes align randomly. This creates different combinations of maternal and paternal chromosomes in gametes, increasing genetic diversity.
37. What is the biological purpose of meiosis in sexually reproducing organisms?
Answer
Meiosis reduces the chromosome number by half to produce haploid gametes, ensuring the zygote has the correct diploid number after fertilization.
38. How does crossing-over differ from mutation in generating genetic diversity?
Answer
Crossing-over is a natural, reciprocal exchange of DNA between homologous chromosomes, while mutation is a random change in DNA sequence. Both increase diversity, but crossing-over is planned and recombinational.
39. Why are cells genetically different after meiosis but not after mitosis?
Answer
Meiosis includes crossing-over and independent assortment, which shuffle genetic material. Mitosis does not, so it produces identical daughter cells.
40. What happens if a gamete with an extra chromosome is involved in fertilization?
Answer
The resulting zygote will have three copies of that chromosome (trisomy), which can lead to disorders like Down syndrome (trisomy 21).
41. Why is prophase I of meiosis longer and more complex than prophase in mitosis?
Answer
Prophase I includes pairing of homologs (synapsis), crossing-over, and formation of tetrads, all of which are absent in mitotic prophase.
42. What does it mean when a gene is said to be “linked” to another gene?
Answer
Linked genes are located close together on the same chromosome and tend to be inherited together unless separated by crossing-over.
43. Describe what happens during telophase I of meiosis.
Answer
In telophase I, homologous chromosomes reach opposite poles, the nuclear envelope reforms, and the cell undergoes cytokinesis, forming two haploid cells.
44. What is the difference in DNA content between cells at the beginning and end of meiosis?
Answer
The starting cell is diploid with duplicated chromosomes; the final cells are haploid with unduplicated chromosomes.
45. Why do polar bodies form during oogenesis?
Answer
Polar bodies form to discard extra chromosomes while preserving cytoplasm in the single functional ovum.
46. How does recombination frequency help map the distance between genes?
Answer
The higher the recombination frequency between two genes, the farther apart they are on the chromosome. This helps establish relative gene order.
47. What distinguishes homologous chromosomes from sister chromatids?
Answer
Homologous chromosomes are similar but not identical chromosomes from each parent. Sister chromatids are identical copies of the same chromosome.
48. What would you expect to observe in a cell during metaphase II?
Answer
Single chromosomes (with sister chromatids) aligned along the metaphase plate in haploid cells.
49. Why does meiosis II resemble mitosis more than meiosis I?
Answer
Both meiosis II and mitosis involve the separation of sister chromatids, unlike meiosis I which separates homologous chromosomes.
50. In what two key ways does meiosis generate genetic diversity?
Answer
Genetic diversity is generated through crossing-over during prophase I and independent assortment of homologous chromosomes during metaphase I.