1) In humans,hemophilia (a disease that affects the blood clotting process) is x
ID: 187391 • Letter: 1
Question
1) In humans,hemophilia (a disease that affects the blood clotting process) is x-linked. A young man,John, has hemophilia but his parents do not.
a)What are the genotypes of John and his parents?
b)If John’s parents have additional children, what are the probabilities that John’s future sisters and brothers will not have hemophilia?
c) Of John’s 4 grandparents, only his father’s father has hemophilia. What are the possible genotypes of the 4 grandparents? From which of the grandparents could John have inherited hemophilia?
Explanation / Answer
Answer:
Xh=hemophilia allele
X=normal allele
In an X linked recessive inheritance, two copies of a disease allele on the X chromosome are required for an individual with two X chromosomes (a female) to be affected with an X-linked recessive trait.
Genotypes of John and his parents
Father= XY
Mother= XhX
If John’s parents have additional children,what are the probabilities that John’s future sisters and brothers will not have hemophilia?
XY x XhX
XXh, XX, XhY, XY
None of John’s sister's would suffer from hemophilia, whereas 50% of John’s brothers would suffer from it.
Of John’s 4 grandparents, only his father’s father has hemophilia. What are the possible genotypes of the 4 grandparents? From which of the grandparents could John have inherited hemophilia?
John's paternal grandfather’s genotype= XhY
John's paternal grandmother's genotype= XhX
John's maternal grandfather’s genotype= XY
John's maternal grandmother’s genotype= XhX
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