Three-point Cross


This time we are looking at the A, B, and C genes (alleles A and a, B and b, C and c). Again, complete dominance for all. Here's our mating:
AaBbCc x aabbcc

If the genes are independent, we should get eight classes of offspring, all pretty much equal in number. However, here's what we get:
ABC: 95 aBC: 50
ABc: 5 aBc: 700
AbC: 700 abC: 5
Abc: 50 abc: 95

Obviously, not all phenotypic classes are equal, so we definitely have linkage.