Question

Analyze the pedigree chart of families A and B given below and select the correct option.

• A. In family A, both the parents are homozygous recessive
• B. In family B, both the parents are homozygous dominant
• C. In family B, both the parents are heterozygous dominant for recessive disorder
• D. In family A, both the parents are heterozygous dominant for recessive disorder

Answer 1

Answer: (D)

STEPS FOR IDENTIFYING THE TYPE OF TRAITS:

• In the case of recessive trait, characteristic condition can appear in the progeny of apparently unaffected parents. Moreover, two affected individuals cannot have unaffected child i.e. either parents or child don’t show the characteristics/disorder.
• If both parents and progeny are affected then the trait is of dominant type.
• If equal no. of males and females are affected in a generation then the trait is of autosomal type.
• If either of the sex is only affected in a generation i.e. only male or female is affected in a generation then the trait is X-linked.
• If only males are affected in a family then the trait is Y-linked. It is also called as holandric inheritance. The genes are called as holandric genes.

Since in family A, both the parents are not affected, but son and daughter are affected equally, the disease has to be autosomal recessive and the parents have to be heterozygous for the character.