KVPY SX SB Exam 20141 Question Paper

Question : 114 of 120

Marks: +1, -0

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

The mutation reverses spontaneously in the third generation
The mutation occurs on the X chromosome and is both recessive and lethal
The mutation occurs on the X chromosome and is both recessive and dominant
The mutation occurs on an autosome and is dominant

Validate

Solution:

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.
XX

^{\m}

→ carrier (survives)
X

^{\m}

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

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