A three-point mapping cross involving the yellow (y) body color, white (w) eye color, and echinus (ec) eye shape genes in Drosophila.

In the F1, females are heterozygous at all three loci and males are hemizygous for the mutant alleles.

Most of the F2 show parental (NCO) phenotypes, with DCOs the least common among the recombinants.