A stock homozygous for three recessive autosomal genes, a, b,and c, not necessarily linked on the same chromosome, ismated to a stock homozygous for their dominant wild-typealleles. F1 females are then backcrossed to males of thehomozygous recessive parental stock and the following cross results are observed:

Phenotype Number Phenotype Number

a bc 42 a b+ 6

+ ++ 48 + +c 4

a ++ 46 a +c 5

+ bc 44 + b+ 5

1. Which of these genes are linked?

2. What is the recombination frequency between the linkedgenes?