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What are the factors that cause mutation?

by scilover89
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scilover89
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Dec3-04, 02:36 AM
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Mutation is one of the important factors to cause evolution, but besides radiation, what cause mutation to happen? Is it happen naturally?
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iansmith
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Dec3-04, 05:34 AM
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The main source of mutation is the DNA polymerase, the enzyme involved in DNA replication. Althought, the process of replication is a high-fidelity one, misparing of nucleotides occurs. The rate is in the range of 1 error every billion base pair to 1 error every trillion base pair.

There is also a long list of mutagenic chemical and some are refered to as cancerigenic. Chemicals and radiation are usually not a source of mutation that give rise to evolution. However, chemicals and radiation can increase the odd of cancer.
loseyourname
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Dec3-04, 12:46 PM
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In organisms that reproduce sexually, recombination and crossing over during meiosis are the largest contributors to genetic diversity. It isn't technically a mutation, but can create new genes (heck, sometimes even new chromosomes) and is an important element of evolution as well.

LURCH
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Dec3-04, 03:24 PM
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What are the factors that cause mutation?

I have read of some experiments in the lab where starvation of single cell organisms was found to be a cause of mutation. I believe the explanation given was that malnutrition weekend the DNA polymerase causing flaws in replication. These flaws were, of course, random but in laboratory experiments they would occasionally produce beneficial results. The specific experiment I read about was some bacteria only capable of metabolizing sucrose being placed in an environment with very little sucrose, but plentiful fructose. Apparently, as starvation began to set in, the rate of mutation among new generations of bacteria increased sharply. Eventually, one of these mutations resulted in individual capable of metabolizing fructose. This individual then reproduced prolifically to the very rich growth medium.

I do not know how well-verified this experiment is but, if it proves true, then it would certainly hint at the possibility that other environmental pressures may contribute to mutation as well.
iansmith
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Dec3-04, 04:13 PM
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Quote Quote by LURCH
I have read of some experiments in the lab where starvation of single cell organisms was found to be a cause of mutation. I believe the explanation given was that malnutrition weekend the DNA polymerase causing flaws in replication. These flaws were, of course, random but in laboratory experiments they would occasionally produce beneficial results. The specific experiment I read about was some bacteria only capable of metabolizing sucrose being placed in an environment with very little sucrose, but plentiful fructose. Apparently, as starvation began to set in, the rate of mutation among new generations of bacteria increased sharply. Eventually, one of these mutations resulted in individual capable of metabolizing fructose. This individual then reproduced prolifically to the very rich growth medium.

I do not know how well-verified this experiment is but, if it proves true, then it would certainly hint at the possibility that other environmental pressures may contribute to mutation as well.
Here the experiment you are talking about but is lactose rather than fructose:

The origin of mutants. Cairns J, Overbaugh J, Miller S.
http://www.ncbi.nlm.nih.gov/entrez/q...t_uids=3045565

There now mechanism that have been proposed
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15207867

It appears that stress (glucose starvation) induce the SOS repair system. In this repair system, DNA polymerase IV synthesise DNA. DNA pol. IV is more prone to create error than the DNA polymerases that replicate DNA under normal conditions.
scilover89
#6
Dec4-04, 12:09 AM
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Since virus can alter the DNA in a cell, is it possible that virus is another element of evolution?
iansmith
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Dec4-04, 07:42 AM
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Quote Quote by scilover89
Since virus can alter the DNA in a cell, is it possible that virus is another element of evolution?
Virus can affect the evolution of one organims if they pick up DNA from another organism, transmit it and integrate in the genome. Plasmid and transposon are mobile genetic elements that also modify the genome. The whole process is known as Horizontal gene transfer (HGT) and it has been sugested as a major and powerfull evolutionnary force.

One of the prime example is virulence of Escherichia coli/Shigella and Vibrio cholera. These organisms have had viruses to integrate into their genome and these viral parts are called pathogenicity island (PAI). PAI are the element responsible for the virulence of E. coli, Shigella and V. cholera. Without these viruses, E. coli is a bacteria lives in your intestine and does give trouble, (Shigella is techenicall an virulent E. coli strain and it has a different name for medical reason) and Vibrio lives happely in the water and symbiotic relation with other animals.


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