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Asked by henryjones to Clare, Mariana, Pedro, Robert, Susanne on 19 Nov 2012.
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Robert Insall answered on 19 Nov 2012:
No, they’re accidents. However nature does USE those accidents to try things out.
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Clare Taylor answered on 19 Nov 2012:
Most mutations are completely by accident and as you know, the beneficial mutations sometimes survive in the population to give rise to new genetic traits. In bacteria though, complex mechanisms have evolved to allow the bacteria to mutate under different circumstances! Certain bacteria have evolved to have ‘slippy DNA’ which means that when the DNA is replicated, it is easy for mistakes to be made; although it happens randomly these mistakes are almost deliberate because they are there to turn certain genes on and off. When the gene is on at the right time, these bacteria have an advantage!
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Susanne Muekusch answered on 19 Nov 2012:
HIV is a virus which does mutate a lot, too. The mutations are random and are achieved by a particularly sloppy genome-copy-machine. It is a great strategy for the virus as a population to display a lot of variation. Clones with a good adaption (for example drug resistance) are more likely to be present. The high mutation rate is also the reason why vaccination does not work.
But there are examples of “controlled genetic variation”, which is recombination: In all sexually reproducing organisms there is homologous recombination occuring before the gametes come into existence. Thus maternal and paternal genes are mixed independent of their chromosomes, giving rise to new genotypes.
Another example is from the immune system: Recombination is the trick here to get a huge library of antibodies which all recognise different things. If you are interested, look here:
http://en.wikipedia.org/wiki/V%28D%29J_recombination -
Mariana Campos answered on 21 Nov 2012:
Robert’s point is very good! Mutations are just mistakes and the cells try to fix them. There are many mechanisms in the cell to try to fix those accidents. Sometimes is impossible and they are not correct. Then nature uses them to try things out and sometimes good things come out of those mistakes.
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