Question

All of the following is usually true about an autosomal recessive disease except

• A. Most people with the disease have parents who do not have the disease.
• B. An equal number of males and females get the disease.
• C. If both parents have the disease, 50% of their offspring will have the disease.
• D. If both parents are heterozygous, 75% of their children will not get the disease.
• E. The genes for the disease are not located on the sex chromosomes.

Answer 1

Answer: (C)

If both parents have the disease, 50% of their offspring will have the disease.

The autosomal recessive disease occurs when both the parents have the mutated genes. Out of both the genes, if only one parent passes the gene, then individuakl is called carrier. This means no signs and symptoms of the disease will occur in the individual because the other gene is normal. But if both the parents have the mutated gene then there are 25% chances that the child would have the disease. Recessive diseases occur due to the genes present on autosomes and not the sex chromosome (that decide your sex/gender).

Example: sickle cell anaemia, cystic fibrosis, etc

So, the correct option is 'If both parents have the disease, 50% of their offspring will have the disease'.