The vocal, claw and hair genes of H. flebotomos all are on the same chromosome. The vocal gene is 15 cM to the left of the claw gene and the hair gene is 30 cM to the right of the claw gene. Based on the three-factor data shown below, how much cross-over interference is present in the vocal-claw-hair region of this chromosome?
gene genotype phenotype
VV roar
vocal Vv roar
vv meow
CC sharp
claw Cc sharp
cc dull
HH spotted
hair Hh spotted
hh striped
cross v c h x v c h
V C H v c h-
progeny Roar Sharp Spotted 570
Meow Dull Striped 570
Roar Sharp Striped 280
Meow Dull Spotted 280
Roar Dull Striped 130
Meow Sharp Spotted 130
Roar Dull Spotted 20
Meow Sharp Striped 20
