If the cross described in Problem 18 were made, and if Sb and cu are 8.2 map units apart on chromosome III, and if 1000 offspring were recovered, what would be the outcome of the cross, assuming that equal numbers of males and females were observed?

Alleles A and a are on one pair of autosomes, and alleles B and b are on a separate pair of autosomes. Does crossover between one pair of homologs affect the expected proportions of gamete genotypes? Why or why not? Does crossover between both pairs of chromosomes affect the expected gamete proportions? Why or why not?

You have isolated (1) a streptomycin-resistant mutant (strᴿ) of Chlamydomonas that maps to the chloroplast genome and (2) a hygromycin-resistant mutant (hygᴿ) of Chlamydomonas that maps to the mitochondrial genome. What types of progeny do you expect from the following reciprocal crosses?

mt⁺ strᴿ hygˢ× mt⁻ strˢ hygᴿ
mt⁺ strˢ hygᴿ× mt⁻ strᴿ hygSˢ

Gene R and gene T are genetically linked. Answer the following questions concerning a dihybrid organism with the genotype Rt/rT:

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

Gene R and gene T are genetically linked. Answer the following questions concerning a dihybrid organism with the genotype Rt/rT:

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 5.10.)