Genetics: Analysis and Principles 4th Edition by Robert Brooker

Exercise 9

A researcher has two highly inbred strains of mice. One strain is susceptible to infection by a mouse leukemia virus, whereas the other strain is resistant. Susceptibility/resistance is a polygenic trait. The two strains were crossed together, and all of the F 1 mice were resistant. The F 1 mice were then allowed to interbreed, and 120 F 2 mice were obtained. Among these 120 mice, 118 were resistant to the viral pathogen, and 2 were sensitive. Discuss how many different genes may be involved in this trait. How would your answer differ if none of the F 2 mice had been susceptible to the leukemia virus Hint: You should assume that the inheritance of one viral-resistance allele is sufficient to confer resistance.