A female is married to a haemophilic male. They are having a normal son.
a) Find out the genotype of the mother.
b) This normal son is married to a carrier female. Find out the genotype & phenotype
of the probable offsprings with relative percentage.
Answers
Answer:
No sons of a man with hemophilia will have hemophilia.
All daughters of a man with hemophilia will be carriers (called obligate carriers).
If a carrier has a son, the son has a 50% chance of having hemophilia.
If a carrier has a daughter, the daughter has a 50% chance of being a carrier.
Explanation:
A daughter gets an X chromosome from her mother and an X chromosome from her father. Suppose the X chromosome from her mother has the gene for normal blood clotting. Suppose the X chromosome from her father has the gene for hemophilia.
The daughter will not have hemophilia since the normal blood clotting gene from her mother is dominant. It won't allow the instructions from the hemophilia gene to be sent.
The daughter is called a carrier for hemophilia. She has the gene on one of her X chromosomes and could pass it on to her children. Does this mean that the mother alone is the one responsible for having a child with hemophilia?
Not really. The mother is the one who passes the hemophilia gene. However, it is the father's sperm that determines if the child will be a boy or a girl. It is not the "fault" of one parent since both parents contribute to the outcome.
All of us have dozens of abnormal genes. We are unaware of most of them. It is purely by chance that a hemophilia gene is passed on to produce a child with hemophilia.
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