Question

Genetic Inheritance: Calculate probability of two children having the same genotype for achrondoplasia Achondroplasia is a common form of dwarfism caused by autosomal dominant mutation in the fibroblast growth factor receptor 3 (Fgfr3) gene. If a person with achondroplasia (Aa) married and had children with a person of normal height, what is the probability that both their first child and second child would have achondroplasia?

Answer 1

The correct answer is - 1/2 or 50% for first and second child to be affected.

Explanation:

Achondroplasia is an autosomal dominant disorder. Autosomal dominant disorder refers to the presence of a single copy of the defective gene that is enough to lead to dwarfness.

A cross of achondroplasia (Aa) parent to a person of normal height (aa) result in half of their children will be affected with dwarfism and the other half will be normal.

a cross between affected or dwarf and normal parent

Aa X aa

Punnett square:

a a

A Aa Aa

a aa aa

Aa- dwarfness

aa- normal height

The probability that both their first child and second child would have achondroplasia is

2/4 =1/2 or 50%.