GENETICS AND EVOLUTION
GENETIC BASIS OF INHERITANCE
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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No, he cannot be a carrier because he has only one x chromosome.
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No, he cannot be a carrier because he has only one Y chromosome.
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Yes, he can be a carrier because he has both an x and Y chromosome.
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Yes, he can be a carrier because he has two x chromosomes.
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Detailed explanation-1: -There are no genes for clotting factors on the Y chromosome. This means that males only have one allele for factor VIII and one allele for factor IX. Thus, if a male has a hemophilia allele on his only X chromosome, he will have the disorder.
Detailed explanation-2: -If the mother has one altered factor gene and the father does not have hemophilia, each son has a 50% chance of having hemophilia and each daughter has a 50% chance of having one altered factor gene, causing her to be a carrier or have hemophilia.
Detailed explanation-3: -The abnormal gene responsible for hemophilia is carried on the X chromosome. Males have one X chromosome and one Y chromosome. In a male, the presence of the abnormal gene results in the deficiency or absence of factor VIII or factor IX, as there is no protective X to make factor VIII or IX.
Detailed explanation-4: -When a female has one affected X chromosome, she is a “carrier” of hemophilia. Being a female carrier of hemophilia is not the same as having hemophilia, although female carriers may experience symptoms of hemophilia. A female carrier can also pass the affected X chromosome on to her children.
Detailed explanation-5: -Since the Y chromosome does not carry the hemophilia gene, a son born to a man with hemophilia and a woman who is not a carrier will not have hemophilia. If the baby gets the X chromosome from the father it will be a girl. The X chromosome from the father with hemophilia will have the hemophilia gene.