Question

Jack’s parents both have achondroplasia (a autosomal dominant disorder) as well as his 2 siblings. He does not have the condition, yet his fiancé’s parents are advising their daughter to not marry and have children with Jack because they had heard that dwarfism runs in families and they are concerned that their grandchildren would be born with this genetic disease. Note that Jack’s fiance is normal height.1. How could you allay the fears of Jack’s fiance and ‘future’ in-laws about the possible condition?

Answer 1

Answer:

Jack is totally free from the disorder and there is zero chance that any of Jack and his normal height fiance's children will have this disease. However, the probability will definitely change if Jack marries someone with the disorder.

Explanation:

The fears of Jack's fiance and future in-laws can be allayed as follows:

Since achondroplasia (a condition characterized by dwarfism and other physical disorders) is an autosomal dominant disorder, it takes only one mutant allele of the gene for the disease to manifest. Consequently, individuals is either affected for the disorder or free from it, there is zero chance of being a carrier.

Jack is free from the disorder because he must have inherited normal alleles from his parents, meaning that each of the parents had one mutant allele and one normal allele for the gene. The 2 siblings of Jack must have inherited the mutant alleles in his stead.

If A represents the allele for the disorder, Jack's parents must have been Aa

Aa   x   Aa = AA (affected), Aa (affected), Aa (affected), aa (not affected)

Jack is the child with aa.

Hence, Jack is totally free from the disorder and there is zero chance that any of Jack and his normal height fiance's children will have this disease. However, the probability will definitely change if Jack marries a dwarf or someone with the disorder.