Final answer:
Sickle-cell anemia is caused by a mutation in hemoglobin's primary structure, where a single glutamic acid is substituted by valine, leading to abnormally shaped red blood cells that can cause blood vessel blockages and serious health complications.
Step-by-step explanation:
Explaining Sickle-Cell Anemia Through Protein Structures
Sickle-cell anemia is a condition that arises from a mutation affecting the primary structure of hemoglobin, the protein responsible for oxygen transport in red blood cells. The primary structure of a protein, which is a sequence of amino acids, determines its shape and function. In sickle-cell disease, a single glutamic acid is replaced by valine in the sixth position of the two beta chains of hemoglobin, altering its secondary, tertiary, and quaternary structures.
This single amino acid substitution significantly impacts the protein structure and function, leading to the abnormal sickle shape of red blood cells that characterizes the disease. A sickled cell's altered shape can cause blockages in blood vessels, leading to severe health issues such as pain, organ damage, and decreased life expectancy.