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 parent genotypes

Let the normal allele be \(A\) and the recessive allele be \(a\). The female who introduces the gene (generation I - yellow - female) is a carrier, so her genotype is \(Aa\). The male in generation I is normal, so his genotype is \(AA\).

Step2: Analyze offspring genotypes

When \(AA\times Aa\), the possible genotypes of their offspring (generation II) are obtained from the Punnett - square analysis. The cross \(AA\times Aa\) gives genotypes \(AA:Aa = 1:1\).

Step3: Calculate carrier probability

Since the female in generation II (asterisk - labeled) does not show the recessive condition, she cannot be \(aa\). The possible genotypes for her are \(AA\) or \(Aa\). The probability of being \(Aa\) (a carrier) out of the non - \(aa\) genotypes is \(\frac{1}{2}\).

Answer:

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