Question

Duchenne muscular dystrophy is a lethal X-linked recessive disease which affects 1 in 3,500 boys.
What is the frequency of carriers of this gene mutation in females?

• A. 1/3,500
  
• B. 1/1,750
• C. 1/59
  
• D. 3/50
  

Answer 1

The correct option is B 1/1,750

In this case, the frequency of the recessive lethal gene or q is 1/3,500.

p+q=1

So, q = 1-1/3500
which is approximately 3499/3500, which approximately 1.

Frequency of carrier or hetrozygote is 2pq.
which is 2 × 1 × 1/3,500 = approximately 2/3,500 or 1/1,750.