Question

If a woman and her husband, who are both carriers, have three children, what is the probability that all three children have the normal phenotype? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16)

Answer 1

Answer: 1/64 would be normal

Step-by-step explanation:

Let the woman phenotype be Yy, since a carrier is usually heterozygous;

Also let the husband phenotype be Yy

Then Yy seperate to yield two alleles "Y" and "y"

So, the cross of the two alleles:

"Y", "y" X "Y", "y"

F1 will be YY, Yy, Yy and yy

From the crossing,

- the normal phenotype are YY,

-the carriers are Yy, Yy

- while yy is recessive.

Since, the probability that one of their offspring is normal is 1/4; for three children, then 1/4 x 1/4 x 1/4 = 1/64

Thus, probability that all three children are normal is 1/64