Question

15 multiple choice 1 point if an affected individual with a recessive autosomal mutation is married to a normal individual, whats the chance for their children to be affected? 0 1/4 1/2 1/1 (100%)

Explanation:

Step1: Recall recessive autosomal mutation genetics

For a recessive autosomal disorder, an affected individual has a genotype of \( aa \) (where \( a \) is the mutant allele, \( A \) is the normal allele). A normal individual is either \( AA \) or \( Aa \). But in typical cases, if we assume the normal individual is homozygous dominant (\( AA \)) (since if they were heterozygous, the problem would likely specify carrier status, and the default for "normal" in basic genetics problems for recessive disorders is homozygous dominant unless stated otherwise).

Step2: Analyze the cross

The cross is \( aa \) (affected) × \( AA \) (normal). Using Punnett square:

• Gametes from \( aa \): all \( a \)
• Gametes from \( AA \): all \( A \)
• Offspring genotypes: all \( Aa \), which are heterozygous and phenotypically normal (since the mutation is recessive, only \( aa \) shows the affected phenotype). So the chance of children being affected is 0.

Answer:

0 (corresponding to the option with "0")