Question

Study the pedigree chart given below. What does it show?

• A. inheritance of a condition like phenylketonuria as an autosomal recessive trait
• B. the pedigree chart is wrong as this is not possible
• C. inheritance of a recessive sex-linked disease like haemophilia
• D. inheritance of a sex-linked inborn error of metabolism like phenylketonuria

Answer 1

Answer: (A)

This chart shows inheritance of an autosomal recessive trait like phenylketonuria. An autosomal recessive trait may skip a generation. It appears in case of marriage between two heterozygous individuals (Aa x Aa = 3 Aa + 1 aa), a recessive individual with hybrid (Aa x aa = 2 Aa + 2 aa) and two recessive (aa x aa = all aa). Phenylketonuria is an inborn, autosomal, recessive metabolic disorder in which homozygous recessive individual lacks the enzyme phenylalanine hydroxylase. The heterozygous individuals are normal but carriers.