Question

a woman has severe neurofibromatosis type 1. she has brown spots on her skin and several large tumors beneath her skin. a gene test shows that her son has inherited the disease-causing autosomal dominant allele, but he has no symptoms

Answer 1

Neurofibromatosis type 1 is an autosomal dominant disorder where inheriting only one mutated gene can lead to the disease. A heterozygous parent with the disease (Nn) has a 50% chance to pass the mutated gene to their offspring. Symptoms may vary due to variable expressivity.

Step-by-step explanation:

Understanding Autosomal Dominant Inheritance with Neurofibromatosis Type 1

Neurofibromatosis type 1 is an example of an autosomal dominant genetic disorder, which means that it is enough for a child to inherit one copy of the mutated gene from a parent to express the disease. In this specific case, a woman with severe neurofibromatosis type 1 has a son who has inherited the disease-causing dominant allele but is yet to show symptoms. This scenario illustrates variable expressivity, where individuals carrying the dominant allele might have different degrees of manifestation of the genetic condition.

Looking at the genetic inheritance, if one parent is heterozygous for neurofibromatosis (Nn) and the other parent is homozygous normal (nn), there is a 50% chance of their children inheriting the condition. This is because the offspring might receive either the mutated gene (N) from the affected parent or the normal gene (n) from the unaffected parent. A Punnett square could be used to predict this inheritance pattern, showing that the genotypes Nn, Nn, nn, and nn are all possible, each with a 25% probability. The presence of symptoms depends on factors such as age of onset and variability in genetic expressivity.