Glucose-6-phosphate dehydrogenase deficiency (G6PD)is inherited as a recessive allele of an X-linked gene in humans.A woman whose father suffered from G6PD marries a normal man.(a)What proportion of their sons is expected to be G6PD? (b)If the husband was not normal but was G6PD deficient,would you change your answer in part (a)?

Question

Quizplus · Accepted Answer

(a) The woman is a carrier of the G6PD allele because she inherited it from her father, who had the disease. This means she has one normal X chromosome and one with the G6PD allele. When she has a son, the son has a 50% chance of inheriting the normal X chromosome from his mother and a 50% chance of inheriting the X chromosome with the G6PD allele. If he inherits the latter, he will have G6PD. Therefore, the proportion of their sons expected to be G6PD is 1/2 or 50%. 
(b) If the husband is also G6PD deficient, then he will have the G6PD allele on his X chromosome, and all of their sons will inherit this allele from him. This means that all of their sons will be G6PD deficient. Therefore, the proportion of their sons expected to be G6PD is still 1/2 or 50%.

Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD)is Inherited as a Recessive Allele of an X-Linked