In fruit flies, black body (b) is recessive to gray body (b+), purple eyes (pr) is recessive to red
eyes (pr+), and vestigial wings (vg) are recessive to normal wings (vg+). The loci coding for
these traits are linked, with the following map distances:
The interference among these genes is 0.2. A fly with black body, purple eyes and vestigial
wings is crossed with a fly homozygous for gray body, red eyes and normal wings. The female
progeny are then crossed with males that have black bodies, purple eyes, and vestigial wings. If
1000 progeny are produced from the testcross, what will be the phenotypes and proportions of
Gene map data along with interference can be used for estimation of phenotypes. Interference data helps in calculation of coefficient of coincidence. Coefficient of coincidence, on other hand, is the ratio of observed double cross over frequency and expected double crossover frequency. With the help of these data parental type, single cross over and double cross over progenies are estimated.