Question

if a girl with sickle cell anemia is born to parents who are healthy, and a parent with sickle cell anemia, what are the genotypes of the girl and the parents? use the punnett square to show the cross and the offspring. probabilities genotypes % phenotypes % punnett square parents a b a a

Explanation:

Step1: Determine the mode of inheritance

Sickle - cell anemia is an autosomal recessive disorder. Let the normal allele be \(A\) and the mutant allele be \(a\). Since the girl has sickle - cell anemia, her genotype is \(aa\).

Step2: Determine the parents' genotypes

The parents are healthy. But they have a child with sickle - cell anemia (\(aa\)). Each parent must have contributed one \(a\) allele. So, the parents' genotypes are \(Aa\) (carriers).

Step3: Create the Punnett square

	\(A\)	\(a\)
\(a\)	\(Aa\)	\(aa\)

Step4: Calculate probabilities

• Genotype probabilities: \(AA: 25\%\), \(Aa: 50\%\), \(aa: 25\%\)
• Phenotype probabilities: Healthy (\(AA + Aa\)): \(75\%\), Sickle - cell anemia (\(aa\)): \(25\%\)

Answer:

• Girl's genotype: \(aa\)
• Parents' genotypes: \(Aa\) and \(Aa\)
• Genotype \(\%\): \(AA: 25\%\), \(Aa: 50\%\), \(aa: 25\%\)
• Phenotype \(\%\): Healthy: \(75\%\), Sickle - cell anemia: \(25\%\)