Study the given pedigree chart showing the inheritance of a genetic disorder in a family. What is the probability that the first child (III-1) born to the couple II-2 and II-3 will be affected by the disorder?

Step-by-step solution

From the pedigree, unaffected parents I-1 and I-2 have an affected daughter II-1. This indicates that the trait is autosomal recessive. Let the recessive allele be ' a ' and the dominant allele be ' A '. Since I-1 and I-2 are unaffected but have an affected child ( aa ), both must be heterozygous ( Aa ). Individual II-2 is an unaffected child of I-1 and I-2. The probability that II-2 is a carrier ( Aa ) is 2 3 (since the possible genotypes for an unaffected child are AA and Aa in a 1:2 ratio). Individual I-3 is aff