Individuals who are homozygous for sickle cell have what condition?

Individuals who are homozygous for sickle cell have sickle cell disease. This condition arises when both alleles for the beta-globin gene, which encodes a part of hemoglobin, carry the mutation that causes the production of abnormal hemoglobin (hemoglobin S). When a person inherits the sickle cell gene from both parents, the resulting hemoglobin cannot effectively carry oxygen, leading to the deformation of red blood cells into a sickle shape. This shape causes various complications, including vaso-occlusive crises, anemia, infections, and damage to organs due to impaired blood flow.

In contrast, individuals with sickle cell trait have one normal allele and one sickle cell allele, resulting in a milder form of the disease where they are typically asymptomatic and have a normal life expectancy. Normal hemoglobin refers to the genotype where both alleles are unaffected and produce standard hemoglobin (hemoglobin A). Carriers of thalassemia would have a different genetic disorder involving a different mutation affecting the production of hemoglobin, and they do not exhibit symptoms of sickle cell disease.

Thus, being homozygous for sickle cell specifically leads to sickle cell disease, characterized by the presence of two mutated copies of the hemoglobin