Test Bank for Genetics, A Conceptual Approach, Update Seventh Edition by Benjamin A. Pierce

Test Bank for Genetics, A Conceptual Approach, Update Seventh Edition by Benjamin A. Pierce 17. Pea plants have seven different types of chromosomes. A chromosome with a centromere at the very end is called a. submetacentric. b. metacentric. c. acrocentric. d. acentric. e. telocentric. Answer: e Section 2.2 Comprehension 18. A dividing eukaryotic cell is treated with a drug that inhibits the molecular motors associated with kinetochores. At which cell cycle stage would it stop? a. G1 b. S c. G2 d. M (metaphase) e. M (telophase) Answer: d Section 2.2 Application 19. Pea plants have seven different types of chromosomes. The nucleus of a megaspore in a pea ovary would contain how many chromosomes? a. 3 ½ b. 7 c. 14 d. 21 e. 30 Answer: b Section 2.3 Comprehension (2) Crossing over. In meiosis I—prophase—portions of homologous chromosomes exchange, changing combinations of alleles of genes on a single chromosome, so not even sister chromatids are identical after crossing over. Each gamete has only one copy of each homolog, and each homolog now has a unique combination of alleles. Section 2.3 Comprehension 46. List two differences and two similarities between mitosis and meiosis. Answer: Differences: (1) Mitosis occurs in somatic (nonsex) cells; meiosis occurs in sex cells to produce gametes. (2) Meiosis involves chromosome pairing (of homologous chromosomes); mitosis does not. (3) Mitosis produces nonsex cells; meiosis produces gametes. (4) Mitosis produces cells of the same ploidy; meiosis produces haploid cells from diploid cells. (5) Meiosis has two consecutive divisions; mitosis has one. (6) Mitosis produces two daughter cells; meiosis produces four daughter cells. (7) Mitosis produces identical daughter cells; meiosis produces four different daughter cells. Similarities: (1) Both involve the separation of replicated chromosomes during cell division. (2) Both are processes to ensure that daughter cells in cell division receive a complete set of chromosomes. (3) DNA replication must occur first. (4) Cytokinesis usually occurs at the end of each. Section 2.2-2.3 Application 47. Describe the difference between homologous chromosomes and sister chromatids. Answer: Homologous chromosomes can have different alleles. Sister chromatids are duplicates and (except for errors in replication) are identical in sequence. Section 2.3 Application 48. Describe the difference between meiosis I and meiosis II. Answer: Homologs pair and segregate in meiosis I. Sister chromatids are paired and segregate in meiosis II. Crossing over occurs in meiosis I but not in meiosis II. Section 2.3 Application 49. Describe the difference between the sporophyte and gametophyte. Answer: The sporophyte is the diploid phase of a plant life cycle. The gametophyte is the haploid stage.