In the general population, what is the probability that an individual will have the birth defect, assuming that maternal and paternal genes

0.0625

Step-by-step explanation:

The prevalence of gene a = 25 %, P (a) = 0.25

birth defect occurs when both parents have prevalence of gene a.

P (Defect) = P (Both parents have gene a)

If both parents inherit the gene a independently, the the individual will have a birth defect when both parents have gene a.

P (Father having gene a) = 0.25

P (Mother having gene a) = 0.25

Hence,

P (Birth Defect) = P (Both parents have gene a) = 0.25 * 0.25 = 0.0625