AP BIOLOGY

Detailed explanation-1: -Sickle cell disease (SCD) is a genetic disorder caused by a mutation in both copies of a person’s HBB gene. This gene encodes a component of hemoglobin, the oxygen-carrying protein in red blood cells. The mutation causes hemoglobin molecules to stick together, creating sickle-shaped red blood cells.

Detailed explanation-2: -Base substitutions are the simplest type of gene-level mutation, and they involve the swapping of one nucleotide for another during DNA replication. For example, during replication, a thymine nucleotide might be inserted in place of a guanine nucleotide.

Detailed explanation-3: -The mutation causing this disease occurs in the 6th codon of the HBB gene encoding the hemoglobin subunit (-globin), a protein, serving as an integral part of the adult hemoglobin A (HbA), which is a heterotetramer of 2 chains and 2 chains that is responsible for binding to the oxygen in the blood.

Detailed explanation-4: -Mutations in the HBB gene cause sickle cell disease. The HBB gene provides instructions for making one part of hemoglobin. Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin.