Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 65

When an abnormal organism has three copies of a chromosome and therefore contains three copies of the genes on that chromosome (instead of the normal number of two copies), the alleles for each gene usually segregate so that a gamete will contain one or two copies of the gene. Let's suppose that an abnormal pea plant has three copies of the chromosome that carries the height gene. Its genotype is TTt. The plant is also heterozygous for the seed color gene, Yy , which is found on a different chromosome. With regard to both genes, how many types of gametes can this plant make, and in what proportions (Assume that it is equally likely that a gamete will contain one or two copies of the height gene.)