homework 8
8.01 Nondisjunction may happen in either division I or division II of meiosis.
8.01 Nondisjunction may happen in either division I or division II of meiosis.
(a) Assuming nondisjunction occurs in meiosis I for the sex chromosomes in a male, what sperm genotypes would be possible?
(a) Assuming nondisjunction occurs in meiosis I for the sex chromosomes in a male, what sperm genotypes would be possible?
(b) If each of these possible sperm were to fertilize a normal egg, what are the possible results?
(b) If each of these possible sperm were to fertilize a normal egg, what are the possible results?
(c) Answer questions a and b again but assume that the nondisjunction happens in meiosis II.
(c) Answer questions a and b again but assume that the nondisjunction happens in meiosis II.
8.02 In humans, there are several well known conditions that result from nondisjunction and thus have incorrect numbers of chromosomes. For each of the following, how many autosomes, X chromosomes, and Y chromosomes would be present in each cell?
8.02 In humans, there are several well known conditions that result from nondisjunction and thus have incorrect numbers of chromosomes. For each of the following, how many autosomes, X chromosomes, and Y chromosomes would be present in each cell?
(a) An male who is trisomic for chromosome number 21 (Down Syndrome)
(a) An male who is trisomic for chromosome number 21 (Down Syndrome)
(b) An female who is trisomic for chromosome number 21 (Down Syndrome)
(b) An female who is trisomic for chromosome number 21 (Down Syndrome)
(c) A female who is monosomic for the sex chromosomes (Turner Syndrome)
(c) A female who is monosomic for the sex chromosomes (Turner Syndrome)
(d) A male who is trisomic for the sex chromosomes (Kleinfelter Syndrome)
(d) A male who is trisomic for the sex chromosomes (Kleinfelter Syndrome)
8.03 Chromosome abnormalities such as duplications, deletions, and inversions can happen by breakage and rejoining of chromosomes.
8.03 Chromosome abnormalities such as duplications, deletions, and inversions can happen by breakage and rejoining of chromosomes.
(a) Using diagrams similar to those in the text, show how a reverse duplication might be generated.
(a) Using diagrams similar to those in the text, show how a reverse duplication might be generated.
(b) Show how a displaced duplication might be generated.
(b) Show how a displaced duplication might be generated.
8.04 Polyploids can result in greater numbers of phenotypes and genotypes for a single gene when compared with the same gene in a diploid. Consider the following questions:
8.04 Polyploids can result in greater numbers of phenotypes and genotypes for a single gene when compared with the same gene in a diploid. Consider the following questions:
(a) How many copies of a gene does an autotetraploid have?
(a) How many copies of a gene does an autotetraploid have?
(b) Assuming that there are two kinds of alleles possible at a particular locus, A and a, there would be five possible genotypes. What are they?
(b) Assuming that there are two kinds of alleles possible at a particular locus, A and a, there would be five possible genotypes. What are they?
(c) If A is dominant to a, how many possible phenotypes would you expect?
(c) If A is dominant to a, how many possible phenotypes would you expect?
8.05 Polyploids have various degrees of fertility.
8.05 Polyploids have various degrees of fertility.
(a) Why are autopolyploids almost always sterile while allopolyploids are frequently fertile?
(a) Why are autopolyploids almost always sterile while allopolyploids are frequently fertile?
(b) If an allopolyploid is formed by fertilization of a haploid egg of one species by a haploid sperm of a different species, would you expect the resulting hybrid to be fertile? If not, what event might cause it to become fertile at some later time?
(b) If an allopolyploid is formed by fertilization of a haploid egg of one species by a haploid sperm of a different species, would you expect the resulting hybrid to be fertile? If not, what event might cause it to become fertile at some later time?