In genetics, the mutation rate is a measure of the rate at which various types of mutations occur during some unit of time. Mutation rates are typically given for a specific class of mutation, for instance point mutations, small or large scale insertions or deletions. The rate of substitutions can be further subdivided into a mutation spectrum which describes the influence of genetic context on the mutation rate.

There are several natural units of time for each of these rates, with rates being characterized either as mutations per base pair per cell division, per gene per generation, or per genome per generation. The mutation rate of an organisms is an evolved characteristic and is strongly influenced by the genetics of each organisms, in addition to strong influence from the environment. The upper and lower limits to which mutation rates can evolve is the subject of ongoing investigation.

Different genetic variants within a species are referred to as alleles, and so a new mutation is said to create a new allele. In population genetics, each allele is characterized by a selection coefficient, which measures the expected change in an alleles frequency over time. The selection coefficient can either be negative, corresponding to an expected decrease, positive, corresponding to an expected increase, or zero, corresponding to no expected change. The distribution of fitness effects of new mutations is an important parameter in population genetics and has been the subject of extensive investigation Although measurements of this distribution have been inconsistent in the past, it is now generally thought that the majority of mutations are mildly deleterious, that many are have little effect on an organisms fitness, and that a few can be favorable. As a result of natural selection, unfavorable mutations will typically be eliminated from a population while favorable changes are quickly fixed, and neutral changes accumulate at the rate they are created by mutations.

Malcolm John "Mac" Rebennack, Jr. (born November 21, 1940), better known by the stage name Dr. John (also Dr. John Creaux, or Dr. John the Night Tripper), is an American singer-songwriter, pianist and guitarist, whose music combines blues, pop, jazz as well as zydeco, boogie woogie and rock and roll.

Active as a session musician since the late 1950s, he came to wider prominence in the early 1970s with a wildly theatrical stage show inspired by medicine shows, Mardi Gras costumes and voodoo ceremonies. Rebennack has recorded over 20 albums and in 1973 scored a top-20 hit with the jaunty funk-flavored "Right Place Wrong Time", still perhaps his best-known song.

The winner of five Grammy Awards, Rebennack was inducted into the Rock and Roll Hall of Fame by singer John Legend on Monday, March 14, 2011.

Born in New Orleans, Louisiana, United States, Dr. John's Acadian ancestry traces back to the imperial territory of Alsace-Lorraine. He claims that his lineage took root in New Orleans sometime in the early 1800s. Growing up in the Third Ward, Dr. John found early musical inspiration in the minstrel tunes sung by his grandfather and a number of aunts, uncles, and cousins who played piano. He did not take music lessons before his teens, he only endured a short stint in choir before getting kicked out. His father, the owner of an appliance store and record shop, exposed him as a young boy to prominent jazz musicians like King Oliver and Louis Armstrong. Throughout his adolescence his father's connections enabled him access to the recording rooms of burgeoning rock artists such as Little Richard and Guitar Slim. From these exposures he advanced into clubs and onto the stage with varying local artists, most notably, Professor Longhair.