Which situation is an example of modifier gene action?
A)A mother and father both have type O blood, and their son is born with type B blood.
B)Two children in the same family both have sickle cell disease, but one child has more severe symptoms than the other.
C)Monozygotic twins separated at birth and raised in two different countries are of different heights (3 inches) and different weights (25 pounds).
D)A woman who has a gene mutation for diabetes mellitus type 2 delays the onset of the disease by exercising and maintaining a normal weight.

Question

Quizplus · Accepted Answer

A gene's degree of expression (disease severity) and timing of expression can be affected by modifier genes and other conditions. Although the gene abnormality that causes sickle cell disease is exactly the same for everyone with the disorder, how severely it is expressed can be changed by modifier genes (which are not always known).

Which Situation Is an Example of Modifier Gene Action