Do Mobile Genetic Elements Accelerate Mutation Events?

[jimmydasaint]

Just a thought - if DNA based transposable elements exist in high enough numbers then should they not cause an increase to the number of mutation events in evolution history, causing a larger variety of genetic mutations than point mutations which are neutral (or even those point mutations which may be deleterious)?

 

So are transposable elements Nature's acceleration pedal for mutation prior to selection?

 

Any views?

 

http://en.wikipedia.org/wiki/Transposon

[Psycho]

Indeed, they do cause nearly random mutation within organisms and they are used for this function in gene mapping as well as finding out the function of genes by studying the phenotype of organisms with transposon insertion mutations.

 

However most organisms have methods of removing transposons or stopping transposition as to stop it occurring within essential genes this is also thought to be one of the reasons why multiple gene copies of certain proteins occur to help stop this process effecting the phenotype.

[jimmydasaint]

Thanks for the reply but it seems a bit confusing. From the viewpoint of the organisms, it seems that they have been selected to STOP these mobile elements from moving around the genome.

 

I have also heard of gene duplications taking place in order to resist the actions of anti-tumour chemicals during step-wise treatment ( increasing dosages of anti-tumour agents being administered to tumour cells in vitro and gene duplication events taking place at each treatment until the numbers increased with increasing dosage).

 

I would appreciate references. Thanks.

[Psycho]

Thanks for the reply but it seems a bit confusing. From the viewpoint of the organisms, it seems that they have been selected to STOP these mobile elements from moving around the genome.

RNA interference is one of the key ideas thought to be behind stopping transposition due to transposition being able to cause lethal insertion mutations. Mutation in terms of an individual organism is a very bad thing as normally mutations will end with a "worse" phenotype for the current environment, it is rare for a positive mutation to occur as many of the enzymes are close to their optimal activity. In any case placing a transposon in definitely won't help the most likely chance of a positive mutation is a single point mutation with a similar amino acid such as a phenylalanine for a tyrosine.

 

Transposon silencing

I have also heard of gene duplications taking place in order to resist the actions of anti-tumour chemicals during step-wise treatment ( increasing dosages of anti-tumour agents being administered to tumour cells in vitro and gene duplication events taking place at each treatment until the numbers increased with increasing dosage).

Gene duplication is thought to happen for many reasons, some of course just by accident but this copy is usually suppressed and therefore has the chance of being able to mutate freely without selection pressures into different types of enzymes, this is thought to be a way that enzyme families evolved.

 

Other reason why it occurs is so protein expression can be faster and in higher quantities due to multiple transcription sites being able to produce mRNA faster.

 

The idea that gene duplications that stop anti-tumour chemicals is a logical assertion as the main selection pressure on the tumour cell is the chemical.

Edited April 12, 2009 by Psycho