If the first child is heterozygous and the wife is homozygous for an autosomal-recessive gene, what will be the outcome?: (A) 75% children affected, (B) No child affected, but all are carriers, (C) 50% children affected, rest are carriers, (D) 25% children affected, rest are carriers
Answer is C. If the husband is heterozygous and the wife is homozygous for an autosomal recessive gene, 50% of the children will be affected; the rest will be carriers. This is pseudo-dominant inheritance, which refers to the observation of apparent dominant (parent to child) transmission of a known autosomal-recessive disorder, or it can also mean the inheritance of a recessive trait mimics a dominant pattern. This occurs when a homozygous affected individual has a paner who is a heterozygous carrier, and their children have 1 in 2 chance to get affected (50%) Ref: Nelson textbook of pediatrics 21st edition Pgno: 645