The mother has sickle cell anemia; father is normal; chances of children having sickle cell disease and sickle cell trait respectively are:
**Core Concept**
Sickle cell disease is an autosomal recessive genetic disorder caused by a mutation in the HBB gene encoding hemoglobin beta chains. The disease is characterized by the substitution of glutamic acid with valine at position 6 of the beta-globin chain, resulting in abnormal hemoglobin S (HbS) that polymerizes under low oxygen conditions, leading to sickling of red blood cells.
**Why the Correct Answer is Right**
In a normal individual, both HBB alleles are wild-type (normal). In a person with sickle cell disease, both alleles are mutated (HbS/HbS). In a person with sickle cell trait, one allele is mutated and the other is normal (HbS/Hb). When a normal individual (HbHb) mates with a person with sickle cell disease (HbSHbS), the possible genotypes of their offspring are:
- 50% chance of inheriting the mutated allele from the mother and a normal allele from the father (HbS/Hb), resulting in a child with sickle cell trait.
- 50% chance of inheriting two mutated alleles (HbSHbS), resulting in a child with sickle cell disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we'll skip it.
**Option B:** This option is also not provided, so we'll skip it.
**Option C:** This option is not provided, so we'll skip it.
**Option D:** This option is also not provided, so we'll skip it.
**Clinical Pearl / High-Yield Fact**
Sickle cell disease is a classic example of a recessive genetic disorder, where a single copy of the mutated gene (sickle cell trait) does not cause the disease but increases the risk of passing it to offspring.
**Correct Answer:** C. 50% chance of sickle cell disease and 50% chance of sickle cell trait.