Question

Dentinogenesis imperfecta is a rare, autosomal, dominantly inherited disease of the teeth that occurs in about one in 8000 people (Witkop, 1957). The teeth are somewhat brown in color, and the crowns wear down rapidly. Assume that a male with dentinogenesis imperfecta and no family history of the disease marries a woman with normal teeth. What is the probability that: a.their first child will be a girl with dentinogenesis imperfecta?

Answer 1

The answer is 25%.

Step-by-step explanation:

Let's say that x represents the gene for the disease. Dentinogenesis Imperfecta is an autosomal dominant disease which means one must possess either a genotype of Xx, one dominant and one recessive, or XX, two dominant genes for the disease to be observed.

Since the individual has no history of the said disease, we can say that his genotype regarding the disease must be Xx which means it has a 50% chance of affecting the child.

The probability of their first child being a girl is 50% and the probability of the child inheriting the disease is also 50% so we can calculate that the probability of both of these conditions being true at the same time is 25%.

I hope this answer helps.