PHENYLKETONURIA:
Cause: This inborn error of metabolism is also inherited as the autosomal recessive trait. The affected individual lacks a liver enzyme called phenylalanine hydroxylase that converts the amino acid phenylalanine into tyrosine. The genes for the disease are located on chromosome no. 12.
SICKLE-CELL ANAEMIA:
Cause: As it is an autosomal recessive disease therefore it can be transmitted from parents to the offspring when both male and female individuals are carriers (heterozygous) for the gene. The genes are located on chromosome number 11.
Thalassemia:
Cause: Thalassaemia is a recessive autosomal genetic defect. The genes for it are present in chromosome no. 11 (Beta-thalassemia) or chromosome no. 16 (Alpha thalassemia).
HEMOPHILIA: (Bleeder’s disease/Royal disease):
Cause: It is an X-linked recessive trait, therefore, showing its transmission from normal carrier female (heterozygous) to male progeny. Due to the presence of a defective form of blood clotting factor (protein), exposed blood of affected individuals fails to coagulate.