Answer:
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Step-by-step explanation:
1.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. The HBB gene provides instructions for making beta-globin.
or
Sickle-cell anemia is the result of a change in a single nucleotide, and it represents just one class of mutations called point mutations.