Chapter 2 Mitosis and Meiosis1) If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?A) 8B) 16C) 32D) 64E) 128Answer: CSection: 2.42) In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?A) 13B) 26C) 52D) 104E) 208Answer: BSection: 2.43) In a healthy male, how many sperm cells would be expected to be formed from (a) 400 primary spermatocytes? (b) 400 secondary spermatocytes?A) (a) 800; (b) 800B) (a) 1600; (b) 1600C) (a) 1600; (b) 800D) (a) 400; (b) 400E) (a) 100; (b) 800Answer: CSection: 2.54) In a healthy female, how many secondary oocytes would be expected to form from 100 primary oocytes? How many first polar bodies would be expected from 100 primary oocytes?A) 200; 50B) 100; 50C) 200; 300D) 100; 100E) 50; 50Answer: DSection: 2.51Copyright © 2012 Pearson Education, Inc.5) The ant, Myrmecia pilosula, is found in Australia and is named bulldog because of its aggressive behavior. It is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) Which of the following figures would most likely represent a correct configuration of chromosomes in a metaphase I cell of a female?A) B) C) D) E) Answer: ASection: 2.46) For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmeciapilosula contains 2 picograms of DNA. How much DNA would be expected in a metaphase I cellof a female?A) 16 picogramsB) 32 picogramsC) 8 picogramsD) 4 picogramsE) Not enough information is provided to answer the question.Answer: DSection: 2.42Copyright © 2012 Pearson Education, Inc.7) Myrmecia pilosula actually consists of several virtually identical, closely related species, with females having chromosome numbers of 18, 20, 32, 48, 60, 62, and 64. Assume one crossed a female of species (A) with 32 chromosomes and a male of species (B) with 9 chromosomes (males are haploid, and each gamete contains the n complement). How many chromosomes would one expect in the body (somatic) cells of the female offspring?A) 4.5B) 9C) 25D) 32E) 41Answer: CSection: 2.48) What is the outcome of synapsis, a significant event in meiosis?A) side-by-side alignment of nonhomologous chromosomesB) dyad formationC) monad movement to opposite polesD) side-by-side alignment of homologous chromosomesE) chiasma segregationAnswer: DSection: 2.49) During interphase of the cell cycle, ________.A) DNA recombinesB) sister chromatids move to opposite polesC) the nuclear membrane disappearsD) RNA replicatesE) DNA content essentially doublesAnswer: ESection: 2.310) Assume that the somatic cells of a male contain one pair of homologous chromosomes (e.g., AaAb), and an additional chromosome without a homolog (e.g., W). What chromosomal combinations would be expected in the meiotic products (spermatids) of a single primary spermatocyte? (There may be more than one answer.)Answer: AaW, AaW, Ab, Ab or Aa, Aa, AbW, AbWSection: 2.411) Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome anda normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.Answer: One-half of the offspring would be expected to have Down syndrome because of 2 × 1 segregation of chromosome #21 at anaphase I.Section: 2.43Copyright © 2012 Pearson Education, Inc.12) Normal diploid somatic (body) cells of the mosquito Culex pipiens contain six chromosomes.Assign the symbols AmAp, BmBp, and CmCp to the three homologous chromosomal pairs. The "m" superscript indicates that the homolog is maternally derived; the "p" indicates a paternally derived homolog. Assume that in the genus Culex, the sex chromosomes are morphologically identical.(a) For each of the cell types given below, draw and label (with reference to the symbols defined above) an expected chromosomal configuration.Mitotic metaphaseMetaphase of meiosis IMetaphase of meiosis II(b) The stage at which "sister chromatids go to opposite poles" immediately follows which of thestages listed in (a)?(c) Assuming that all nuclear DNA is restricted to chromosomes and that the amount of nuclear DNA essentially doubles during the S phase of interphase, how much nuclear DNA would be present in each cell listed above? Note: Assume that the G1 nucleus of a mosquito cell contains 3.0 × 10-12 grams of DNA.(d) Given that the sex of Culex is determined by alleles of one gene, males heterozygous, Mm, and females homozygous, mm, illustrate a labeled chromosomal configuration (involving the symbols AmAp, BmBp, and CmCp and the M locus) in a primary spermatocyte at metaphase. Assume that the M locus is on the AmAp chromosome and that crossing over has not occurred between the M locus and the centromere.4Copyright © 2012 Pearson Education, Inc.Answer: (a)(b) Metaphase of meiosis II and mitotic metaphase(c) 6, 6, 3(d)Section: 2.55Copyright © 2012 Pearson Education, Inc.13) Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in thefemale, two chromosomal pairs are metacentric and that two pairs are acrocentric.(a) Draw the chromosomal configurations as you would expect to see them at the stages listed:Mitotic metaphase First polar body (metaphase)Primary oocyte (metaphase) Ootid(G1)Secondary oocyte (metaphase)(b) Given that the above-mentioned cells are from individuals heterozygous for two independently segregating, autosomal loci, plum eyes and curled wings, place appropriate symbols (of your designation) on chromosomes in the drawings you made in part (a) above. Assume no crossing over, and there may be more than one correct answer in some cases.(c) Assuming that a somatic G2 nucleus from the individuals mentioned above contains about 8.0picograms of DNA, how much nuclear DNA would you expect in each of the cells mentioned above?Answer: (a,b)(c) 8, 8, 4, 4, 2Section: 2.56Copyright © 2012 Pearson Education, Inc.14) Down syndrome, or trisomy 21, in humans is caused by an extra copy of the relatively small,acrocentric chromosome #21. Including only chromosome #21, the X chromosome