Final answer:
A missense mutation is a genetic alteration where a single amino acid in a protein is replaced by another. If the new amino acid is similar in chemical properties to the original, the mutation's impact on the protein may be minor. However, if there's a significant difference, as in sickle cell disease, it can have severe effects.
Step-by-step explanation:
The question refers to a type of genetic mutation known specifically as a missense mutation. A missense mutation occurs when a point mutation in the DNA sequence causes one amino acid to be replaced by a different amino acid in a protein.
When the new amino acid is chemically similar to the original amino acid, the effects on the protein's function might be minimized or negligible. This is an example of the genetic code's degeneracy, a property that can reduce the impact of mutations on an organism. For instance, a missense mutation that substitutes aspartate for glutamate may have less severe consequences because both are negatively charged amino acids.
In contrast, if the missense mutation causes the substitution of an amino acid with significantly different properties, such as what happens in sickle cell disease, it can lead to serious health problems. In the case of sickle cell disease, a mutation substitutes glutamic acid, which is polar, with valine, a nonpolar amino acid, significantly altering the protein's function.