Like Hurler syndrome Fabry disease involves an abnormal accu

Like Hurler syndrome, Fabry disease involves an abnormal accumulation of substances within lysosomes. However, the lysosomes of individuals with Fabry disease show an abnormal accumulation of lipids. The defective enzyme is -galactosidase A, which is a lysosomal enzyme that functions in lipid metabolism. This defect causes cell damage, especially to the kidneys, heart, and eyes. The gene that encodes -galactosidase A is found on the X chromosome. Let\'s suppose a phenotypically unaffected couple produces two sons with Fabry disease and one phenotypically unaffected daughter. What is the probability that the daughter will have an affected son?

Solution

Answer: The probability that the daughter will have an affected son= 50% or 1/2

Explanation:

Unaffected couple means that female is normal but heterozygous(X^FX^f) and the male is normal (X^FY).

F= Normal allele; f= diseased allele.

X^FX^f    x X^fY------Parents

All females are normal (phenotypically) 50% : Normal male, 25% : Diseased male, 25%

Genetically normal female (50%) : heterozygous female (50%)

The daughter is phenotypically unaffected means that she would have e heterozygous normal. If the daughter consists of a son,the probability of affected son is 50%. Because sons will get X chromosome from the mother.

X^FX^f = 50% X^F & 50% X^f