Question

Assume that a recessive allele (f) is associated with a severe language disorder. An unaffected male wants to determine the genotypes of his wife, his parents, and himself. His mother has the language disorder. Neither he nor his wife has the language disorder, but one of their five children does. What is the genotype for each individual?

Answer 1

His mother has the language disorder but he doesn't have the language disorder. That means the disease must be recessive and he must carry 1 defect gene. So the male would be heterozygous. His father could be heterozygous or homozygous dominant.

A recessive gene only expressed with 2 alleles, 1 from both parents. One of their five children does. His child that has the disease should get it from his gene and his wife gene. So, his wife at least has 1 defect gene. Since his wife is normal, then she must be heterozygous.