Can someone point me to a recent article on strand asymetry in DNA
damage, repair, or mutations? I'm looking at some genes which have
undergone a lot of mutations at CpG sites. CpG becomes methylated in mammals
then the 5-methyl-C can deaminate to become a T, which is not repaired by
damage-recognition enzymes because it is not damage, it is just a mispairing.
Anyway, if the C on one strand mutaties at the same rate as the
C on the other strand we should see an equal number of CpG -> TpG
mutations and CpG -> CpA mutations. This is not the case. There are
many more CpG -> TpG mutations.
The statistical analysis is a bear because the CpG dinucleotide does
no occur in all reading frames equally. If CpG occurs mainly with the C of
the mRNA-like (noncoding) strand in the third position of the codons this
means that the G is in the first position of a codon and the G -> A will
result in (Val -> Leu, Ala -> Pro and so on) amino acid changes. Thus I
need to take this into account when deciding if I am seeing strand asymetry
of repair, or just selection against amino acid changes.
--
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* Brian Foley * If we knew what we were doing *
* Molecular Genetics Dept. * it wouldn't be called research *
* University of Vermont * *
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