Question

Study the pedigree chart given below.

It demonstrates:

• A. Inheritance of a recessive sex-linked disease.
• B. Inheritance of a sex-linked disease.
• C. Inheritance of an autosomal recessive condition.
• D. The pedigree chart is wrong as this is not possible

Answer 1

The correct option is C

Inheritance of an autosomal recessive condition.

Phenylketonuria is an inherited autosomal recessive disease that causes an increase in the blood of a chemical known as phenylalanine. In the parental generation, none of the parents is affected. So the allele responsible is not dominant. Since all both males and females from healthy parents are affected, the allele has to be autosomal and not sex linked.

This pedigree chart thus shows autosomal recessive disease.