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.

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]. Not all scientists agree with the common 'molecular clock'. The review in Science’s ‘Research News’ goes still further about Eve’s date, saying that ‘using the new clock, she would be a mere 6000 years old.’ The article says about one of the teams of scientists (the Parsons team) that ‘evolutionary studies led them to expect about one mutation in 600 generations ... they were “stunned” to find 10 base-pair changes, which gave them a rate of one mutation every 40 generations.’ This means the mutation rate is still not clear to scholars.

[edit] References

^ Nachman, Michael W. & Crowell, Susan L. 2000. Estimate of the Mutation Rate per Nucleotide in Humans. Genetics 156, 297-304.
^ 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.
^ Peter J. Russell, Fundamentals of Genetics, Addison Wesley, ISBN 0-321-04868-7, 412