Question

This pedigree shows inheritance of which condition?

• A. Colour blindness
• B. Phenylketonuria
• C. Hemophilia
• D. Down's syndrome

Answer 1

The correct option is B Phenylketonuria

Since, both a son and a daugther are affected in F${}_1$, the disorder is not sex-linked. So, it has to be autosomal. If the trait was dominant, then, the parents also would have been affected. Hence, the trait has to be controlled by a recessive gene. So, this pedigree is of autosomal recessive disorder, like phenylketonuria (PKU) and thalassemia.

Colour blindness and hemophilia are X-linked disorders.
Down's syndrome is chromosomal aneuploidy.