What type of disorder is Sickle cell anemia?

Sickle cell anemia is classified as a recessive autosomal disorder because it is caused by mutations in the HBB gene located on chromosome 11, which encodes the beta-globin subunit of hemoglobin. For a person to exhibit the symptoms of sickle cell anemia, they must inherit two copies of the mutated gene—one from each parent. This characteristic is typical of recessive disorders, where two copies of the recessive allele are necessary for the phenotype to manifest. Carriers, who possess only one copy of the mutated gene (heterozygous), usually do not show symptoms of the disease but can pass the mutation to their offspring.

In contrast, dominant disorders would require only one copy of the mutated allele to express the disorder, which is not the case with sickle cell anemia. X-linked disorders are linked to genes on the X chromosome, affecting males and females differently due to differences in sex chromosome composition, which is also not applicable here. Lastly, polygenic disorders arise from the interaction of multiple genes and typically involve quantitative traits rather than a single gene mutation leading to a specific phenotype like sickle cell anemia.