Question

8.7. interpret a human pedigree to determine whether a given condition is recessive, dominant, or sex - linked. 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? generation i ii iii normal female normal male unaffected male female introducing gene into family click or tap a choice to answer the question. 0% 33% 50% 75% 100%

Explanation:

Step1: Define alleles

Let the normal allele be $A$ and the recessive disease - causing allele be $a$. The female in generation I who is a carrier has the genotype $Aa$, and the male in generation I is assumed to be $AA$ (since there is no indication of the trait in him).

Step2: Perform Punnett - square analysis

When $AA$ (male) and $Aa$ (female) have offspring, the possible genotypes of their offspring (generation II) are obtained from the Punnett - square. The cross is $AA\times Aa$. The possible genotypes of the offspring are $AA:Aa = 1:1$.

Step3: Calculate the probability

The probability that a female in generation II is a carrier ($Aa$) is $\frac{1}{2}=50\%$.

Answer:

$50\%$