Genetic testing has found that Gary, Ben, Tara, and Matt all carry a copy of a gene for hemophilia. However, Tara, who is the only female out of the four, does not show any signs of the disease, whereas Gary, Ben, and Matt have developed the disease. In this scenario, it can be inferred that hemophilia is most likely a(n)
A) X-linked disease.
B) sex-linked chromosomal abnormality.
C) gene-linked abnormality.
D) autosomal dominant disorder.

Question

Quizplus · Accepted Answer

Hemophilia is most commonly inherited as an X-linked recessive trait, meaning that it is caused by an abnormality on the X chromosome. Females have two X chromosomes, whereas males only have one. If a male inherits the abnormal X chromosome, he will develop the disease because he does not have a backup healthy X chromosome. However, females will only develop the disease if they inherit the abnormal X chromosome from both parents, which is less likely to occur. In this scenario, Tara must have inherited the abnormal X chromosome from one parent, but her other healthy X chromosome is able to compensate for the abnormality and prevent the development of the disease. Gary, Ben, and Matt, who are all male, only have one X chromosome which makes them more vulnerable to the disease.

Genetic Testing Has Found That Gary, Ben, Tara, and Matt