# If both parents are carriers for thalessemia, which is an autosomal recessive disorder, what are chances of pregnancy resulting in an affected child?a) 100%b) no chancec) 50%d) 25%

AA-Normal
Aa-Carrier
aa-Disease

$\text {Affected}=\frac{1}{4}=25 \%$

An autosomal recessive disorder like thalassemia is caused by abnormalities in both members of a pair of genes. Both parents may carry a single dose of the gene on one chromosome but have a normal gene on the other chromosome, which prevents the appearance of the disease in the carrier parent. A child must get one abnormal gene from each parent in order to be affected by the disease. Parents who are both carriers of an autosomal recessive disorder have a 25% risk of producing an offspring affected by the disease and a 50% risk of producing normal-appearing carriers.

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