Question

Achondroplasia, a condition that causes certain types of dwarfism, is a genetic disorder with dominant inheritance (A). Which of the following represents the gametes an individual heterozygous for achondroplasia would produce?
A) All Aa
B) All A
C) $50\%$ A and $50\%$ a
D) All a
E) None of the above.

Answer 1

Achondroplasia is an autosomal dominant disorder, in which the ossification process is affected. Parents affected with achondroplasia pass on the disorder to the offspring, both males and females are equally affected.

Complete answer: Achondroplasia is a disorder with short-limbed dwarfism. The term achondroplasia means” without cartilage formation.” In achondroplasia, mainly in long bones of arms and legs, cartilage is not converted to bone, which means the process of ossification is defective.
It is an autosomal dominant disease (means one copy of the gene in each cell can cause the disorder), where there is a mutation in the fibroblast growth factor receptor 3 gene (FGFR3). If one of the parents with the defected FGFR3 gene, passes it on to the child, the child will develop the disorder.
Achondroplasia is the most common type of short-limbed dwarfism. One out of 10,000 individuals may be affected by the disorder (has low cases of incidence).
Achondroplasia is an autosomal disease, both the sex with defected genes will be equally affected.
An individual with heterozygous (Aa) for achondroplasia, will produce two types of gametes, ie. $50\%$ A and $50\%$ a.
Therefore, our correct option is C. $50\%$ A and $50\%$ a.

Note: A term similar to achondroplasia is hypochondroplasia. Hypochondroplasia is also an autosomal dominant disorder where a mutation in the triggering factors slows the cell growth and such individuals have fewer height differences.