Question

Very urgent! Please help me!!


Red-green Color Blindness and Hemophilia A are both sex-linked traits in humans. Both genes are on the X-chromosome and are tightly linked.

Individual 1 is homozygous normal woman married to individual 2 who is both red-green color blind and a hemophiliac.Individual 3 is their daughter who married to a normal man individual 4 and individual 5 is the as yet unborn son of them.



What is the probability that their son, individual 5, will be both color blind and a hemophiliac?

Answer 1

So the mother is normal XX
The father is color blind XiY (the i indicates that the gene is affected)

To be color blind and hemophiliac a woman needs to have XiXi and a man needs XiY
This is both the same for color blindness and hemophilia.
A woman can also be XiX. This would mean she is a carrier of the affected gene but not affected by the disease.

Their daughters will all be carriers because only the X chromosome of the man is affected.
This drawing explains it:


Theire daughter with genotype XXi marries a man with genotype XY
(the daughter is carrier for both color blindness and hemophilia)
If they get children they'll end up according to the next drawing:


So the chance that their son will have both the diseases is 50%

Answer 2

1 out of 4

Answer 3

50%

Answer 4

Hi thomaster and maaxx, Thanks heaps for your great help!!! :)))

Answer 5

Thanks for your clear explanation F1 generation and F2 table was very useful!

Answer 6

thomaster! Thanks for the assistance and direction! Best regards!