John has hemophilia,a sex-linked,blood-clotting disorder transmitted by a recessive gene.Neither his mother nor his father has symptoms of this disease.What can we conclude about the genetic makeup of John's parents?

Question

Quizplus · Accepted Answer

Since hemophilia is a recessive sex-linked disorder, it means that the affected gene is located on the X chromosome. John could only have acquired this disorder if he inherited the faulty gene from his mother because for males, they only receive one X chromosome from their mother. Since neither of John's parents have symptoms of hemophilia, his father does not have the faulty gene. Therefore, John's mother must be a carrier of hemophilia, meaning she has one normal X chromosome and one X chromosome with the faulty gene.

John Has Hemophilia,a Sex-Linked,blood-Clotting Disorder Transmitted by a Recessive Gene