Image Based Question – 66330

The chances of having an unaffected baby, when both the parents are suffering from the condition as shown in the picture below is ?

A. 0%.

B. 25%.

C. 50%.

D. 100%.

Show Answer

Correct Answer » B Explanation

In the picture above, both the parents are suffering from achondroplasia.

In accordance with an autosomal dominant inheritance pattern the chances of having an unaffected baby are 25%.

Achondroplasia is an autosomal dominant condition.

• Let ‘a’ represent the normal allele and A represent the achondroplasic allele.

Given that both parents have achondroplasia, the most favourable inheritance would be :

• 3 out of 4 children would be affected or 75% of children will be affected

• 1 out of 4 i.e. 25% children will be unaffected.

Note: We have chosen only a heterozygous state in both parents as the question is asking about the most favourable outcome possible. If both parents are homozygous 0% children will be unaffected.