Vitamin-D resistant rickets is a sex-linked dominant trait,which leads to softening of the bones which can cause fractures and deformities.Rickets is often due to a deficiency of vitamin D,however,with vitamin-D resistant rickets,ingestion of vitamin D is ineffective.Maria's mother is normal and does not display any symptoms of this disease; however,Maria's father has the disease.Maria marries a man that does not have the disease.What is the probability that they will have a daughter that has the disease?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Question

Quizplus · Accepted Answer

Since vitamin-D resistant rickets is a sex-linked dominant trait and Maria's father has the disease, Maria must have inherited the affected X chromosome from her father. Therefore, Maria is a carrier of the disease. When Maria, who is heterozygous for the trait (X^DX^d), marries a man without the disease (X^dY), there is a 50% chance that their daughter will inherit the affected X chromosome (X^DX^d) and have the disease.

Vitamin-D Resistant Rickets Is a Sex-Linked Dominant Trait,which Leads to Softening