Question

In a species of fly, smooth wings (W) are dominant to wrinkled wings (w) and red bodies (R) are dominant to yellow bodies (r).

A WwRr and wwrr fly mate and produce the following offspring:

• Smooth, red: 778
• Smooth, yellow: 162
• Wrinkled, red: 158
• Wrinkled, yellow: 785

What is the genetic distance between both genes?

Group of answer choices

12 cM

24 cM

20 cM

17 cM

Answer 1

The distance between two genes can be calculated using the equation

Total number of recombinant/ Total number of progenies X 100

In the given question parents are Smooth Red and Yellow wrinkled. There are four types of offsprings and whose numbers are,

1. Smooth Red - 778

2. Smooth yellow - 162

3. Wrinkled red - 158

$. Wrinkled yellow - 785

The total number of progenies is 1883. In this, the 1 and 4 groups of progenies are similar to their parents and 2 and 3 are recombinants as compared to the parent. Then total number of recombinants is 320. As per the equation, the distance between two genes =Total number of recombinant/ Total number of progenies X 100

= 320/1883 X 100 = 16.99= 17 cM.

Hence in the given options option 4 is correct