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10. Meiosis and Genetic Diversity — Practice Questions
This chapter explores the phases of meiosis and how they generate genetic variation, including crossing-over, independent assortment, and errors like nondisjunction that contribute to chromosomal abnormalities.
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(Multiple Choice — Click to Reveal Answer)
1. What is the final result of meiosis in terms of chromosome number and genetic content?
(A) Two diploid identical cells
(B) Two haploid different cells
(C) Four haploid identical cells
(D) Four haploid genetically unique cells
Answer
(D) — Meiosis creates four genetically unique haploid gametes.
2. During which phase of meiosis do homologous chromosomes separate?
(A) Prophase I
(B) Anaphase I
(C) Anaphase II
(D) Telophase II
Answer
(B) — Homologous chromosomes separate in anaphase I.
3. How many chromosomes are in each gamete produced by a diploid organism with 8 chromosomes?
(A) 2
(B) 4
(C) 8
(D) 16
Answer
(B) — Gametes have half the number of chromosomes: 4 in this case.
4. What stage of meiosis involves crossing-over?
(A) Prophase I
(B) Metaphase I
(C) Anaphase II
(D) Telophase II
Answer
(A) — Crossing-over occurs during prophase I when homologous chromosomes pair up.
5. What ensures genetic variation during metaphase I of meiosis?
(A) Chromosome condensation
(B) Crossing-over
(C) Independent assortment
(D) Cytokinesis
Answer
(C) — Independent assortment during metaphase I results in varied chromosome combinations.
6. What term describes chromosomes failing to separate during meiosis?
(A) Synapsis
(B) Recombination
(C) Segregation
(D) Nondisjunction
Answer
(D) — Nondisjunction is the failure of chromosomes to separate, leading to abnormal numbers.
7. Which of the following is true about meiosis but not mitosis?
(A) Involves sister chromatid separation
(B) Occurs in somatic cells
(C) Results in diploid cells
(D) Involves homologous chromosome pairing
Answer
(D) — Homologous chromosomes pair up during meiosis, not mitosis.
8. How many cell divisions occur in meiosis?
(A) 0
(B) 1
(C) 2
(D) 4
Answer
(C) — Meiosis consists of two cell divisions: meiosis I and meiosis II.
9. What best describes a gamete?
(A) A diploid body cell
(B) A haploid sex cell
(C) A fertilized egg
(D) A cell in G0 phase
Answer
(B) — Gametes are haploid reproductive cells like sperm and egg.
10. What results from recombination during meiosis?
(A) Genetically identical chromatids
(B) Chromosome duplication
(C) New allele combinations
(D) Deletion of DNA
Answer
(C) — Recombination creates new combinations of alleles on chromatids.
11. Which of the following occurs during metaphase I of meiosis?
(A) Sister chromatids separate
(B) Homologous chromosomes line up in pairs
(C) Chromosomes decondense
(D) DNA replicates
Answer
(B) — In metaphase I, homologous chromosome pairs align at the metaphase plate.
12. Which process helps maintain the diploid chromosome number across generations?
(A) DNA replication
(B) Fertilization and meiosis
(C) Cell differentiation
(D) Mitosis
Answer
(B) — Meiosis creates haploid gametes, and fertilization restores diploidy.
13. Which type of cell undergoes meiosis?
(A) Liver cell
(B) Skin cell
(C) Germ cell
(D) Muscle cell
Answer
(C) — Germ cells undergo meiosis to form gametes.
14. What is synapsis?
(A) Separation of chromatids
(B) Alignment of centromeres
(C) Pairing of homologous chromosomes
(D) Formation of spindle fibers
Answer
(C) — Synapsis is the pairing of homologous chromosomes during prophase I.
15. Which structure forms after homologous chromosomes pair during meiosis I?
(A) Chromatid
(B) Tetrad
(C) Nucleosome
(D) Chiasma
Answer
(B) — A tetrad consists of four chromatids from two homologous chromosomes.
16. Which event occurs in anaphase II of meiosis?
(A) Homologous chromosomes separate
(B) Sister chromatids separate
(C) Tetrads form
(D) Synapsis occurs
Answer
(B) — In anaphase II, sister chromatids are pulled to opposite poles.
17. What is the chromosome number in human gametes?
(A) 23 pairs
(B) 46 total
(C) 23 total
(D) 46 pairs
Answer
(C) — Human gametes contain 23 single (haploid) chromosomes.
18. Why are the cells produced by meiosis genetically different?
(A) Cytokinesis occurs twice
(B) DNA does not replicate
(C) Crossing-over and independent assortment
(D) Telophase is skipped
Answer
(C) — Crossing-over and independent assortment ensure variation in gametes.
19. Which of the following correctly matches the process with its outcome?
(A) Meiosis — diploid gametes
(B) Mitosis — haploid cells
(C) Meiosis — haploid gametes
(D) Fertilization — haploid zygote
Answer
(C) — Meiosis results in haploid gametes.
20. What term refers to the exchange of genetic material between homologous chromosomes?
(A) Replication
(B) Translation
(C) Recombination
(D) Mutation
Answer
(C) — Recombination or crossing-over creates genetic variation during meiosis.
21. What is one difference between meiosis I and meiosis II?
(A) Meiosis I separates sister chromatids
(B) Meiosis II creates diploid cells
(C) Meiosis I reduces chromosome number
(D) Meiosis II includes synapsis
Answer
(C) — Meiosis I is the reduction division that halves the chromosome number.
22. What happens during telophase II?
(A) Chromosomes replicate
(B) Nuclear membranes reform
(C) Tetrads are formed
(D) Crossing-over begins
Answer
(B) — Telophase II involves reformation of nuclear membranes around chromosomes.
23. What would be the chromosome number of a cell after meiosis II if the diploid number is 12?
(A) 6
(B) 12
(C) 24
(D) 0
Answer
(A) — Meiosis results in haploid cells, so half of 12 is 6.
24. What stage of meiosis ensures the separation of genetic alleles?
(A) Prophase I
(B) Metaphase II
(C) Anaphase I
(D) Telophase I
Answer
(C) — In anaphase I, homologous chromosomes separate, segregating alleles.
25. What kind of error leads to trisomy conditions like Down syndrome?
(A) Synapsis
(B) Nondisjunction
(C) Mutation
(D) Independent assortment
Answer
(B) — Nondisjunction results in gametes with abnormal numbers of chromosomes.
26. Which statement best explains why meiosis increases genetic variation among offspring?
(A) It allows the cell to skip cytokinesis.
(B) It produces diploid cells with different alleles.
(C) It introduces variation through recombination and independent assortment.
(D) It prevents mutations from being inherited.
Answer
(C) — Genetic recombination and independent assortment create new allele combinations in gametes.
27. What is the primary outcome of a nondisjunction event during anaphase II?
(A) Gametes with missing or extra chromosomes
(B) All gametes are identical
(C) DNA replication fails
(D) Crossing-over is prevented
Answer
(A) — Nondisjunction causes unequal chromosome separation, leading to abnormal gametes.
28. Why is there no additional round of DNA replication before meiosis II?
(A) The cell must conserve energy
(B) Chromosomes are already duplicated before meiosis I
(C) DNA would become damaged
(D) Centrosomes do not reform
Answer
(B) — DNA is replicated once before meiosis I; no further replication occurs before meiosis II.
29. Which of the following describes a key feature of recombination frequency?
(A) It is unrelated to gene location
(B) It is higher between genes located close together
(C) It helps determine gene order on chromosomes
(D) It only occurs in mitosis
Answer
(C) — Recombination frequency is used to map genes based on their physical distance on chromosomes.
30. What is the expected genetic outcome of crossing-over between linked genes?
(A) Reduced variation
(B) Identical gametes
(C) New allele combinations
(D) Homologous chromosome loss
Answer
(C) — Crossing-over breaks linkage and creates new allele combinations.
31. What would you expect to observe in a karyotype with a trisomy 21?
(A) One copy of chromosome 21
(B) No chromosomes
(C) Three copies of chromosome 21
(D) Missing sex chromosomes
Answer
(C) — Trisomy 21 means there are three copies of chromosome 21 (Down syndrome).
32. How does meiosis help maintain chromosome number stability in sexually reproducing organisms?
(A) It reduces chromosome number in gametes to half
(B) It increases mutations in zygotes
(C) It prevents fertilization
(D) It eliminates sex-linked traits
Answer
(A) — Meiosis halves the chromosome number so that fertilization restores the diploid state.
33. A gene recombination frequency between gene A and gene C is 30%. Between A and B is 45%, and B and C is 15%. Which is the correct gene order?
(A) A-C-B
(B) B-A-C
(C) A-B-C
(D) C-B-A
Answer
(A) — The lowest recombination frequency (B-C) indicates the closest genes; A is farthest from B.
34. Why might a recombination frequency exceed 50% between two genes?
(A) They are on different chromosomes
(B) Crossing-over is suppressed
(C) They are extremely close together
(D) They are located in the nucleus
Answer
(A) — Genes on different chromosomes assort independently, resulting in a 50% recombination frequency.
35. Which process during meiosis explains Mendel’s law of independent assortment?
(A) Synapsis during prophase II
(B) Separation of sister chromatids
(C) Random orientation of homologous pairs in metaphase I
(D) Fertilization of the zygote
Answer
(C) — In metaphase I, homologous pairs align randomly, causing independent assortment of genes.
36. Explain how crossing-over during meiosis contributes to genetic diversity.
Answer
Crossing-over occurs during prophase I when homologous chromosomes exchange genetic segments. This creates new combinations of alleles on chromatids, increasing genetic variation in offspring.
37. What is the purpose of producing haploid cells through meiosis?
Answer
Haploid gametes ensure that when fertilization occurs, the resulting zygote has the correct diploid chromosome number.
38. Describe the difference in chromosome alignment between metaphase I and metaphase II.
Answer
In metaphase I, homologous chromosome pairs align at the metaphase plate. In metaphase II, individual chromosomes line up single file, similar to mitosis.
39. How does independent assortment occur and what is its genetic significance?
Answer
During metaphase I, homologous pairs align randomly. This means each gamete receives a different combination of maternal and paternal chromosomes, enhancing genetic diversity.
40. What is the role of the chiasma in meiosis?
Answer
The chiasma is the point where homologous chromosomes physically exchange genetic material during crossing-over in prophase I.
41. Why does meiosis involve two cell divisions but only one round of DNA replication?
Answer
DNA is replicated once before meiosis I, but the two divisions separate homologous chromosomes (meiosis I) and sister chromatids (meiosis II), reducing chromosome number to haploid without further replication.
42. How can nondisjunction in meiosis lead to conditions such as Down syndrome?
Answer
Nondisjunction is the failure of chromosomes to separate properly. If this occurs with chromosome 21, a gamete may carry two copies. After fertilization, the resulting zygote has three copies (trisomy 21).
43. Compare the genetic content of the four cells produced by meiosis.
Answer
All four cells are haploid and genetically unique due to crossing-over and independent assortment.
44. What is a tetrad and during which phase does it form?
Answer
A tetrad is a group of four chromatids formed by the pairing of homologous chromosomes. It forms during prophase I.
45. What happens to the centromere during anaphase II?
Answer
The centromeres split, allowing sister chromatids to separate and move to opposite poles of the cell.
46. How does meiosis ensure chromosome number remains stable across generations?
Answer
Meiosis produces haploid gametes, and when two gametes fuse during fertilization, the diploid number is restored.
47. Why do linked genes often get inherited together?
Answer
Linked genes are located close together on the same chromosome, reducing the likelihood of being separated by crossing-over.
48. What is the significance of recombination frequency in genetic mapping?
Answer
Recombination frequency reflects the distance between genes; a higher frequency indicates that genes are farther apart on the chromosome.
49. Define aneuploidy and provide one example.
Answer
Aneuploidy is the presence of an abnormal number of chromosomes in a cell. An example is trisomy 21 (Down syndrome).
50. What happens to homologous chromosomes during anaphase I, and how is this different from anaphase II?
Answer
In anaphase I, homologous chromosomes are separated. In anaphase II, sister chromatids are separated.