Mendelian Disorders

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.

the female parent is heterozygous

Thalassemia differs from sickle-cell anaemia in that
the former is a quantitative problem of synthesising too few globin molecules while the latter is a qualitative problem of synthesising an incorrectly functioning globin.