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