Why is sickle cell anemia in discontinous variation?

Sickle cell anemia is an example of discontinuous variation because it is determined by a single gene with two distinct alleles: the normal hemoglobin allele (A) and the sickle cell allele (S). Individuals can have one of three possible genotypes: AA (normal), AS (carrier), or SS (sickle cell disease), leading to discrete phenotypic categories rather than a continuous range of traits. This clear distinction results in individuals either exhibiting sickle cell symptoms or not, aligning with the concept of discontinuous variation.