Question

Two copies of an abnormal gene must be present in order for the disease or trait to develop in

• A. Autosomal recessive disorder
• B. Autosomal dominant disorder
• C. Sex-linked disorders
• D. Y-linked disorders

Answer 1

The correct option is A

Autosomal recessive disorder

An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.

If both parents are heterozygous, each of their children has a 25% chance of expressing the trait of the recessive allele. If both parents are homozygous recessive, all of the children will express the trait.

Examples: Cystic fibrosis, sickle cell anaemia etc