In the the fruit fly Drosophila, there is a dominant gene for normal wings and its recessive allele for vestigial wings. At another gene locus on the same chromosome, there is a dominant gene for red eyes and its recessive allele for purple eyes. A male that was heterozygous at both gene loci was mated with a female that was homozygous for both recessive alleles and the following results were observed among the offspring:

Normal wings and red eyes - 420
Vestigial wings and red eyes - 80
Normal wings and purple eyes - 70
Vestigial wings and purple eyes - 430

According to these data, what is the distance, in centimorgans, between these 2 gene loci? (Enter the number only without the units. For example, 100 cM would be entered as 100)

According to linkage theory, two genes present on the same chromosome tend to get inherited together. So the gametes produced are not equal in number and parental type offspring are observed more in number than the new recombinant types.

Here, normal wings, red eyes (420) and vestigial wings, purple eyes (430) are most in number hence they are the parental type offspring.

Vestigial wings, red eyes = 80 : recombinant

Normal wings, purple eyes = 70 : recombinant

Distance between two genes in cM = recombination frequency = (total number of recombinants / total progeny)*100

= [(80+70)/(420+80+70+430)]*100

= (150/1000)*100

= 0.15*100 = 15cM