A couple,neither of whom has sickle cell anem | vedclass

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(B) Sickle cell anemia is an autosomal recessive disorder.Since the parents do not have the disease but have an affected child,both parents must be ca

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(B) Sickle cell anemia is an autosomal recessive disorder.Since the parents do not have the disease but have an affected child,both parents must be carriers (heterozygous) for the trait.Let the normal allele be $A$ and the sickle cell allele be $a$.The genotype of both parents is $Aa$.When crossing $Aa 	imes Aa$,the possible genotypes of the offspring are $AA$ (normal),$Aa$ (carrier),$Aa$ (carrier),and $aa$ (affected).The probability of having an affected child $(aa)$ in each pregnancy is $1/4$ or $25\, \%$.

$A$ couple,neither of whom has sickle cell anemia,has a first child who is affected by sickle cell anemia. What is the probability that their second child will have sickle cell anemia (in $, \%$)?

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