Question

6. Phenylketonuria (PKU) is an inherited disease determined by a recessive allele. If

a woman and her husband are both carriers, what is the probability of their
offspring having phenylketonuria?

Answer 1

25%

Step-by-step explanation:

Phenylketonuria is inherited as autosomal recessive trait . Since both the woman and her husband are the carrier of the disease their genotype would be Aa , where A is the dominant allele and a is recessive.

We can make a Punnet square as ,

`\boxed{\begin{array}c \sf{ } & \sf A &\sf a \\\\ \sf A & \sf AA &\sf Aa \\\\ \sf a & \sf Aa &\sf aa \end{array}}`

From this , we can see that only one offspring would receive both the recessive allele and would be affected from the disease.

Hence the probability of their offspring of having PKU will be ,

`\longrightarrow\sf (1)/(4)* 100 =\boxed{\bf 25\% }`