# The probability of two carrier parents having a child with sickle cell anemia is? a)0.25 b)0.50 c)0.75 d)1.0

## Please explain how you got to the answer. The answer is A, I do not understand how to do this question. Use the following information to answer the next question. Sickle cell anemia is an autosomal recessive genetic disorder. Because individuals affected by sickle cell anemia have defective hemoglobin proteins, their blood cannot transport oxygen properly. There appears to be a relationship between the incidence of malaria and sickle cell anemia. Individuals with sickle cell anemia and carriers of the sickle cell allele have some resistance to malaria. Malaria is caused by the parasite Plasmodium and is transmitted among humans by mosquitoes. The probability of two carrier parents having a child with sickle cell anemia is? a)0.25 b)0.50 c)0.75 d)1.0

May 13, 2017

1/4 or 0.25 which is 25% Let's see if I can explain it well enough for you

#### Explanation:

I will direct you to a wonderful punnet square that shows the crossing of two carrier parents. When you cross two heterozygotes, a heterozygote being a person who expresses both the dominant and recessive allele form of a gene, the offspring will show a 3:1 phenotypic pattern.

$\textcolor{m a \ge n t a}{\underline{\textcolor{b l u e}{\text{Phenotype of offsprings}}}}$

• $3 - \text{normal; (AA, AS, AS)}$

• $1 - \text{carries trait for sickle cell disease (SS)}$

The genotype, however, is clearly different for the 3 offsprings that are phenotypically normal .

$\textcolor{m a \ge n t a}{\underline{\textcolor{b l u e}{\text{Genotype for the 3 Normal offspring}}}}$

• 1 expresses homozygous dominant
$\text{AA}$ and,

• the 2 other express the heterozygous dominant form, $\text{AS}$.

The questions asks you to determine the probability of a certain outcome.

There are four likely events , $\text{AA}$, $\text{AS}$, $\text{AS}$, and $\text{SS}$. Out of those four events, you are to figure out the probability of the carrier parents getting a child that expresses the autosomal recessive trait, which in this example is $\text{SS}$. The probability of that event is occuring is 1 out of 4.

color(orange)(1/4->0.25 or 25%

$\text{Answer: 0.25 or 25%}$