Mutations

An example of a spontaneous mutation is sickle-cell anemia, which is the result of a single "base pair substitution" which places valine as the sixth amino acid in the hemoglobin chain instead of glutamate.

This animation (Audio - Important) describes base pair substitution.

In a "frameshift mutation," there may be an insertion or deletion of several base pairs causing a misreading of the mRNA during translation.

This animation (Audio - Important) describes frameshift mutation.

A rather dramatic mutation is that of transposable elements, which are regions of DNA that "jump" to new locations in DNA. When they insert into a gene region, they usually inactivate that gene.

Many gene mutations are spontaneous. Others are caused by mutagens such as UV (ultraviolet) light, ionizing radiation, and alkylating agents. Each gene has a characteristic mutation rate. Average rate for eukaryotes is between 10^-4 and 10^-6 per gene per generation.

Spontaneous mutations are rare and will not endure unless they occur in gametes. A protein that is specified by a heritable mutation may have harmful, neutral, or beneficial effects on an individual's ability to function in the prevailing environment.

REVIEW: The difference between normal hemoglobin and sickle-cell hemoglobin is in the
Answer substitution of a specific amino acid for another specific amino acid.