wild-type crossed with black, vestigial-winged flies
F1 dihybrids, all of which appear wild-type.
A testcross of F1 females with black, vestigial-winged males
produced 2,300 F2 offspring.
- If the 2 genes were on different chromosomes, independent assortment should yield equal
numbers of the 4 types of F2.
- If the 2 genes were on the same chromosome, each allele combination
(B+ vg+ and b vg) should stay together
and only yield parental phenotypes in the F2.
- The high percentage of parental phenotypes in the F2, with some non-parental
(recombinant) phenotypes imply the 2 genes are physically close
to each other on the same chromosome.