One of two major forms of neurofibromatosis results from inheriting a dominant allele of a gene with affected individuals having phenotypes that range from mild to very severe. Which of the following is the best explanation for why a young child is the first in her family to be diagnosed with a severe form of the condition?
A) The mother carries the gene but does not express it.
B) One of the parents has a mild expression of the gene.
C) The condition skipped a generation in the family.
D) The child has one more chromosome than either of the parents.

Question

Quizplus · Accepted Answer

Neurofibromatosis exhibits variable expressivity, meaning the severity of the condition can vary widely among individuals carrying the dominant allele. If one parent has a mild expression of the gene, they can pass it on to their child, who might then exhibit a more severe form of the condition.

One of Two Major Forms of Neurofibromatosis Results from Inheriting