Chapter 5, Problem 21P

Gene $\text{R}$ and gene $\text{T}$ are genetically linked. Answer the following questions concerning a dihybrid with the genotype $\text{Rt/rT}$:

a. If $\text{r = 0}\text{.20}$, give the expected frequencies of gametes produced by the dihybrid.

b. If two crossover events occurred between these two genes, what are the genotypes of recombinant chromosomes?

c. Can you make a general statement about how the occurrence of two crossover events between a given pair of linked genes affects the estimate of recombination frequency? (Hint: Think about this problem for a gene pair with a small recombination frequency versus a gene pair with a much higher recombination frequency. See also Figure $\text{5}\text{.10}$.)