2. Familial incontinentia pigmenti (IP) is an X-linked dominant disorder that ca

Question

2. Familial incontinentia pigmenti (IP) is an X-linked dominant disorder that causes a disturbance of skin pigmentation and can be associated with malformations of the eyes, teeth. and skeleton. The disorder is most often lethal prenatally in males.

a. If a woman who exhibits IP marries a man with no family history of the disease, what is the probability that they will have a child with the disease? Please explain how you determine this probability (3 points)

b. Continuing with the previous problem, the couple's first child is a girl who does not exhibit this disorder. Given that the mother has the disorder, the couple is quite informed about the disorder. After the ultrasound of their second child, they are told that they are expecting a boy. The couple is quite concerned that the woman will not be able to carry the baby to term. However, she is able to give birth to a baby boy. After a week, the couple starts to notice symptoms of IP on the skin of their baby boy. The couple is concerned that their son might die soon. This does not happen. The child is currently two years of age and does not suffer from the disorder. How is this possible? Please explain in 3-4 sentences based upon topics being covered for this exam. (3 points)

Explanation / Answer

Familial incontinentia pigmenti (IP) is an X-linked dominant disorder.

If the women contains the disease, there is possibility that either she had the one X chromosome affected with the gene, as this is X-linked dominant disorder. Presence of the diseased gene in one of the X chromosome is sufficient to got the disease.

lets assume that the female is XaX ( where a= Familial incontinentia pigmenti (IP))

the male if XY

XaX X XY

Xa

X

X

XaX

XX

Y

XaY

XY

50% of daughter can get the disorder, 50% of son can also have the disorder or 50% cases their chikdren can have the disease.

Xa

Xa

X

XaX

Xa X

Y

XaY

XaY

lets assume that the female carries the gene in her bolth X chromosome

Xa

Xa

X

XaX

Xa X

Y

XaY

XaY

If the female carries the gene on both chromosome, then all the children will carry the disrder.

b) The son might escape the Familial incontinentia pigmenti (IP) syndrome either if he has 47, XXY

It is possible that the son has two X chromosome , one of which is normal.

Xa

X

X

XaX

XX

Y

XaY

XY

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