Question

In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males will either have the disease or not (but they won’t ever be carriers)

X H X H = female, normal /  X H Y = male, normal

X H X h = female, carrier

X h X h = female, hemophiliac / X h Y= male, hemophiliac

Show the cross of a man who has hemophilia with a woman who is a carrier. What is the probability that their children will have the disease? __________

7. A woman who is a carrier marries a normal man. Show the cross. What is the probability that their children will have hemophilia? What sex will a child in the family with hemophilia be?

8. A woman who has hemophilia marries a normal man. How many of their children will have hemophilia, and what is their sex?

Answer 1

7.Carrier woman genotype will be XHXh Normal man genotype will be XHY

Cross : XHXh * XHY

Normal Man

Carrier Woman	XH	Y
XH	XHXH normal daughter	XHY normal son
Xh	XHXh carrier daughter	XhY hemophiliac son

There is 25% of chance that daughter will be carrier

There is 25% of chance that son will be hemophiliac

There is 50% of chance that son or daughter will be normal.

The son or male child in the family will be hemophiliac.Hemophilia is a recessive sex linked trait that is found in the X chromosome .As males have only one X chromosome,so a recessive form of the gene when present in the X xhromosome of males/sons will result in hemophilic male /son

8.Woman with hemophilia will have genotype : XhXh Normal man genotype : XHY

Cross : XhXh * XHY

Man

Woman	XH	Y
Xh	XHXh carrier daughter	XhY hemophilic son
Xh	XHXh carrier daughter	XhY hemophilic son

Hemophilia is a recessive sex linked trait that is found in the X chromosome .As males have only one X chromosome,so a recessive form of the gene when present in the X xhromosome of males/sons will result in hemophilic male /son.For a daugheter to be hemophilic, she should possess the recessive form of the genes in both her X chromosomes.She is a carrier for the gene when one X chromosome has recessive gene and the other X chromosome has the dominant gene.Sons will be normal only when the X chromosome has the dominant gene.

So, from the cross above it cab be said that out of 4 children, 2 children will have hemophilia.So,50% of children will be hemophilic.

Their sex will be male child/ sons.