Final answer:
The Beta^S allele in sickle cell anemia results in a single amino acid substitution in the Beta-globin polypeptide, leading to changes in the protein structure and function.
Step-by-step explanation:
In sickle cell anemia, the Beta^S allele leads to a change in the Beta-globin polypeptide. Specifically, it results in a single amino acid substitution in the Beta chain of hemoglobin.
Glutamic acid, which is a hydrophilic amino acid, is replaced by valine, a hydrophobic amino acid, in the sixth position of the Beta chain.
This change in the primary structure of the protein alters its function significantly, causing the red blood cells to change from a rounded shape to a sickle shape, leading to serious complications and a medical condition called sickle cell anemia.