%possessing one or more alleles of tach sach mutation

[Asclepius1]

a married couple is screened to assess the tay sach dis. in their children.the activity of hexoaminidase A in the sera of mother and father are 45% and 55% resp.of the referance value.the couple has one child,what is the probability of the child possessing one or more alleles of tay sach mutation?

0

0.25

0.5

0.75

1.0

[quachtinh]

My answer is 0.25 . Here is my calculation:

.45 x .55 = .2475


This is an AND statement so you have to multiply

This question is probably not going to be on the USMLE

[Asclepius1]

for this question you do not need to calculate, you can always figure it out from the disease!

this type of question will be on the exam but won't be the same format!
everything will be on the exam, don't underestimate!

[Asclepius1]

Hi,

The mom and dad both have approximately 50% levels of hexosaminase. So they have one normal allele and one defective allele.

Lets say both have Tt. Consider T to be normal and t to be defective.

So Tt x Tt could be TT, Tt, Tt or tt

And hence the child getting atleast one defective allele(chance of disease + carrier state) is 75% or 0.75