In article <zxiong.47.000BF7DF at arizvm1.ccit.arizona.edu>,
zxiong at arizvm1.ccit.arizona.edu (Zhongguo Xiong) wrote:
> Let me try to explain it a little better. We have found 16 nucleotide
> substitutions in about 1500 nucleotide of overlapping sequences. There are 11
> C to T or T to C substitutions and 5 G to A or A to G substitutions. We have
> not found any other possible substituions.
>> Is there a theory describing the rule of nucleotide substitution during
> evolution? I feel very ignorant and hope someone can give me a pointer to how
> to explain my observation.
What you describe is the oft observed excess of transitions (A-G or C-T
substitutions) over transversions (i.e. A-T, A-C, others). The pattern
depends upon the type of DNA sequence (coding, non-coding) and other
factors. A good place to start in getting some background and a basic
introduction to molecular evolution is in: Fundamentals of Molecular
Evolution by Wen-Hsiung Li and Dan Graur.
mezwick at ucdavis.edu
Department of Ecology and Evolution
Center for Population Biology