Question

A spontaneous mutation results in a couple having only female progeny. When the daughter marries and has ****, none of them are males. However, in the third generation there are few male offspring. What is the most likely explanation of this observation -

(A) The mutation reverses spontaneously in the third generation

(B) The mutation occurs on the X chromosome and is both recessive and lethal

(C) The mutation occurs on the X chromosome and is both recessive and dominant

(D) The mutation occurs on an autosome and is dominant

Answer 1

Correct option (B) The mutation occurs on the X chromosome and is both recessive and lethal

Explanation:

The mutation that occurred is on x-chromosome and is both recessive and lethal since, female is carrier it survives but due to hemizygous condition male is unable to survive.

XXm → carrier (survives)

XmY → ****

While in third generation, the possibility of male child occurs.