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Practice problem

Substitution (DNA Mutation) — Definition & Examples

By Sylvia Freeman

Sickle cell anemia is caused by a single base change in the gene coding for beta-hemoglobin. Beta-hemoglobin makes up part of hemoglobin, an important protein in red blood cells that binds to oxygen. The mutated beta-hemoglobin can't bind oxygen as well, decreasing blood cells' ability to transport oxygen around the body. The blood cells also have a sickle-like shape, causing them to clump together and get stuck in smaller capillary blood vessels.

An amino acid chart. Non-polar amino acids include alanine, valine, methionine, leucine, isoleucine, proline, tryptophan, and phenylalanine. Basic amino acids include lysine, arginine, and histidine. Acidic amino acids include glutamic acid and aspartic acid. Polar amino acids include tyrosine, threonine, glutamine, glycine, serine, cysteine, and asparagine.

Image by Gabi Slizewska.

The point mutation responsible for sickle cell anemia changes a single amino acid from Glutamine (Glutamic acid) to Valine. Why might this one amino acid change cause the negative symptoms of sickle cell disease?

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