Question

A girl of normal stature is born to two parents with achondroplasia who have very short stature, especially disproportionately short arms and legs. What is the probability (by Punnett square analysis) that any pregnancy this girl eventually has will result in the birth of an infant with achondroplasia if her partner also has normal stature?

Answer 1

Answer:

0%

Explanation:

Achondroplasia is an autosomal dominant disorder that is expressed in both homozygous and heterozygous dominant genotypes. Since two affected parents have a normal girl child, both the parents should be heterozygous carrier for the disease.  Let's assume that the dominant allele "A" is responsible for the disease. Genotype of both the parents of the girl would be "Aa". The genotype of girl with normal stature is "aa". Genotype of her normal partner is "aa".

A cross betwee aa X aa would get all the progeny with "aa" genotype. Therefore, all of their children would have normal stature and there is 0% probability for them to have a child with achondroplasia.