sequence divergence puzzle
James McInerney, Zoology
jamm at nhm.ac.uk
Sun Jan 31 12:05:40 EST 1999
Is it possible that the nucleotide sequences are extremely biased in
their base composition? If you have two random DNA sequences composed of
25% As 25% Ts etc. Then you will have sequences of 25% similarity,simply by
chance. If the sequences are biased towards GC or AT, then the sequences
will be closer to 50% similar, simply by chance. This might be part of
your problem. Of course, this situation might be exacerbated by the fact
that the sequences are not random, but they are related to each other at
Of course, this is simply a guess.
James O. McInerney,
Dept. of Zoology,
The Natural History Museum,
London SW7 5BD.
> I am not an evolutionary biologist but I am in the middle of writing
> my thesis and have a problem understanding this information. I have
> two sialidase genes from streptococcus pneumoniae which are more
> conserved at the nucleotide level (60%) than the amino acid level
> (53%). I thought this was usually the other way round.
> Ive checked the synonymous/nonsynonymous values using jukes-cantor
> theyare 1.2+-0.25/0.46+-0.046.
> Does anyone have any ideas? or other examples like this?
> Sam king
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