Chapter 14, Problem 15
Two mothers give birth to sons at the same time in a busy hospital. The son of couple 1 is afflicted with hemophilia A, which is a recessive X-linked disease. Neither parent has the disease. Couple 2 has a normal son even though the father has hemophilia A. The two couples sue the hospital in court, claiming that a careless staff member swapped their babies at birth. You appear in court as an expert witness. What do you tell the jury? Make a diagram that you can submit to the jury.
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Suppose you are heterozygous for two genes that are located on different chromosomes. You carry alleles A and a for one gene and alleles B and b for the other. Be sure to list all the genetically different gametes that could form and indicate how frequently each type should be observed.
Suppose you are heterozygous for two genes that are located on different chromosomes. You carry alleles A and a for one gene and alleles B and b for the other. On the diagram, identify the events responsible for the principle of segregation and the principle of independent assortment.
The blending inheritance hypothesis proposed that the genetic material from parents is mixed in the offspring. As a result, traits of offspring and later descendants should lie between the phenotypes of parents. Mendel, in contrast, proposed that genes are discrete and that their integrity is maintained in the offspring and in subsequent generations. Suppose the year is 1890. You are a horse breeder who has just read Mendel's paper. You don't believe his results, however, because you often work with cremello (very light-colored) and chestnut (reddish-brown) horses. You know that when you breed a cremello individual from a pure-breeding line with a chestnut individual from a pure-breeding line, the offspring are palomino—meaning they have an intermediate (golden-yellow) body color. What additional cross would you do to test whether Mendel's model is valid in the case of genes for horse color? According to his model, what offspring phenotype frequencies would you get from your experimental cross? Explain why your cross would test Mendel's model versus blending inheritance.
You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows According to these data, is the curved-wing allele autosomal recessive, autosomal dominant, sex-linked recessive, or sex-linked dominant?
You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows. Is the lozenge-eyed allele autosomal recessive, autosomal dominant, sex-linked recessive, or sex-linked dominant?
You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows: What is the genotype of the female parent?