Question

the following pedigree shows the inheritance of an autosomal recessive condition. the yellow female that introduces the gene into the family is a carrier. what are the chances that the female in generation ii labeled with the asterisk is a carrier for this condition?

Explanation:

Step1: Determine the genotypes of parents

Let the recessive allele be \(a\) and the dominant allele be \(A\). The male in generation I (normal) has genotype \(AA\) (since autosomal recessive, and no family history of the recessive condition before the introduced female). The female in generation I (introducing the gene) has genotype \(Aa\) (carrier, as she is the one bringing the recessive gene into the family).

Step2: Analyze the cross \(AA\times Aa\)

Using the Punnett - square for \(AA\times Aa\):

Gametes of male (\(A\))	Gametes of female (\(A\))	Gametes of female (\(a\))

The possible genotypes of offspring (generation II) are \(AA:Aa = 1:1\)

Answer:

The probability that the female in generation II (labeled with asterisk) is a carrier (\(Aa\)) is \(\frac{1}{2}\)