Tuesday, August 28, 2007

Mutation rate

Mutation rate

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In genetics, the mutation rate is the chance of a mutation occurring in an organism or gene in each generation. See Luria-Delbrück experiment. The mutation frequency is the number of individuals in a population with a particular mutation. This is important in fields such as evolutionary biology and oncology.

In evolutionary biology, mutations can have a neutral, favorable or unfavorable effect on the organism, with respect to the present environment. The effect of a low mutation rate on a population is that few variations are available to respond to sudden environmental change. This means the species is slower to adapt. A higher mutation rate damages more individuals, but by providing more variation in the population thereby increases the speed at which the population can adapt to changing circumstances.

Mutation rates differ between species and even between different regions of the genome of a single species. For example, mutations in so-called Junk DNA which do not affect organism function tend to accumulate mutations at a faster rate than DNA which is actively in use by in the organism (gene expression). A region which mutates at predictable rate is a candidate for use as a molecular clock.

If the mutation rate of a gene is assumed to be constant (clock like) the degree of difference between the same gene in two different species can be used to estimate how long ago two species diverged (see molecular clock). In fact, the mutation rate of an organism may change in response to environmental stress. For example UV light damages DNA, which may result in error prone attempts by the cell to perform DNA repair.

The human mutation rate is higher in the male germ line (sperm) than the female (egg cells), but estimates of the exact rate have varied by an order of magnitude or more.[1].[2]

More generally, the mutation rate in eukaryotes is in generally 10-4 to 10-6, and for bacteria and phages the rate is 10-5 to 10-7 per gene per generation[3].

[edit] References

  1. ^ Nachman, Michael W. & Crowell, Susan L. 2000. Estimate of the Mutation Rate per Nucleotide in Humans. Genetics 156, 297-304.
  2. ^ Kumar, Sudhir & Subramanian, Sankar. 2002. Mutation rates in mammalian genomes. Proceedings of the National Academy of Sciences of the United States of America. 99, 803-808.
  3. ^ Peter J. Russell, Fundamentals of Genetics, Addison Wesley, ISBN 0-321-04868-7, 412

[edit] See also


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