Essential Genetics 6th Edition by Daniel Hartl

Exercise 12

A Drosophila cross is carried out with a female that is heterozygous for both the y (yellow body) and bb (bobbed bristles) mutations. Both genes are located in the X chromosome. Among 200 male progeny, there were 49 wildtype for both traits, 51 with yellow body, 41 with bobbed bristles, and 59 mutant for both genes. Do these genes show evidence for linkage? [Note: The appropriate chi-square test is a test for a 1 : 1 ratio of parental : recombinant gametes.]