what are the odds that two carriers for cystic fibrosis, an autosomal recessive disorder, would have an…

what are the odds that two carriers for cystic fibrosis, an autosomal recessive disorder, would have an offspring with the cystic fibrosis disorder? 0/4 1/4 1/2 3/4

what are the odds that two carriers for cystic fibrosis, an autosomal recessive disorder, would have an offspring with the cystic fibrosis disorder? 0/4 1/4 1/2 3/4

Answer

Explanation:

Step1: Define alleles

Let the normal allele be $A$ and the mutant allele be $a$. Carriers have the genotype $Aa$.

Step2: Set up Punnett - square

When two carriers ($Aa\times Aa$) have offspring, the possible gametes from each parent are $A$ and $a$. The Punnett - square has 4 possible combinations: $AA$, $Aa$, $aA$, and $aa$.

Step3: Determine affected genotype

The genotype for an individual with cystic fibrosis (autosomal recessive) is $aa$. Out of the 4 possible genotypes from the Punnett - square ($AA:Aa:aA:aa = 1:2:1$), the proportion of $aa$ is $\frac{1}{4}$.

Answer:

1/4