Final answer:
The accumulation of genes for sickle cell disease is explained by the heterozygote advantage, where individuals carrying one copy of the mutated gene have increased resistance to malaria, a benefit that maintains the presence of the gene in the population.
Step-by-step explanation:
Accumulations of gene forms for genetic diseases like sickle cell disease are best explained by understanding the genetics and evolutionary dynamics behind the condition. Sickle cell anemia is an autosomal recessive disease caused by a mutation in the hemoglobin gene, resulting in erythrocytes taking on a sickle shape.
These sickled cells can clog blood vessels and lead to complications like severe pain, tissue damage, and anemia. Notably, the persistence of the sickle cell gene among people of African descent is linked to the fact that being heterozygous for the trait confers a protective advantage against malaria, a deadly disease prevalent in Africa.
Individuals who are heterozygous for the sickle cell gene carry one normal hemoglobin gene and one sickle cell gene, resulting in sickle cell trait. These individuals usually do not suffer from the severe symptoms of sickle cell anemia, but crucially, they are less susceptible to the severe effects of malaria. This is an example of a phenomenon known as heterozygote advantage, which has maintained the allele in the population despite its potentially harmful effects in homozygous individuals who inherit two copies of the mutated gene.