Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 3

You again want to map the positions of three genes ( L , M , and N ) in Drosophila. Each gene has one dominant allele and one recessive allele. You perform the three different two-factor crosses (Cross 1: LM and lm, Cross 2: MN and mn, and Cross 3: LN and ln ). Assume all crosses are between diploid flies homozygous for the alleles of these genes. You observe 5% recombinants in the first cross, 50% recombinants in the second cross, and 50% recombinants in the third cross. Based on the data given, what can you determine for the gene order and distance between the genes?