Question

In one of the genetic disorders affecting central nervous system, the homozygous recessive individuals (tt) are affected at an early age. Which of the following statements is correct for a fatal disease to be carried in a population?

• A. If one parent is heterozygous, the offspring have a $25\%$ chance of being heterozygous.
• B. If one parent is heterozygous, the offspring have a $75\%$ chance of being heterozygous.
• C. If one parent is heterozygous, the offspring have a $100\%$ chance of being heterozygous.
• D. If one parent is heterozygous, all offspring have a $25\%$ will be carriers.
• E. If one parent is heterozygous, the offspring have a $50\%$ chance of being heterozygous.

Answer 1

The correct option is E If one parent is heterozygous, the offspring have a $50\%$ chance of being heterozygous.

According to the question, a cross between Tt and tt parent will give homozygous recessive and heterozygous dominant progeny in 1:1 ratio. This makes option E correct answer.

Tt--> tt	T	t
t	Tt heterozygous dominant	tt homozygous recessive