Mutations: Transitions vs Transversions

[Monique]

I am wondering, are there certain statistical probabilities of mutations? Like, which one is more likely a transistion or a transversion (and what do they mean)?

 

[iansmith]

transition is from a purine to purine (G to A or A to G) or from pyrimidine to pyrimidine (T to C or C to T) whereas a transversion is from purine to pyrimidine or pyrimidine to a purine.

Transition is more common because purine and pyrimidine and quite different and it's easier for the repair enzyme to detected a transversion.

 

[LURCH]

Originally posted by Monique
I am wondering, are there certain statistical probabilities of mutations? Like, which one is more likely a transistion or a transversion (and what do they mean)?

Just attempting to apply the principal of natural selection to the question, it would seem that some mutations would necessarily be more likely than others. See if this makes sense; a mutation that improves the survivability of the organism will be perpetuated to future generations. Certain types of mutation bear a stronger statistical probability of being beneficial than others (the ability to digest different food sources comes immediately to mind). Natural selection should ensure that the gene-copying process more likely to produce one of these beneficial types of mutation would be selected by environmental pressures, in the same way that the mutations themselves are selected. The result would be that all life on Earth (everything that has survived this long) should have a built in tendency to favor certain sorts of mutation over others.