Answer:
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
