Welcome to this, the third thread to attempt to cover convergent tendencies in DNA and their implications for evolutionary theory and phylogenetics.
In their PLOS paper Vowles and Amos show that small microsatellite repeat regions of DNA can influence local sequences and predispose them to certain mutations (
Vowles and Amos, 2004).
(Vowles and Amos,2004) writes:
Microsatellites are a major component of the human genome, and their evolution has been much studied. However, the evolution of microsatellite flanking sequences has received less attention, with reports of both high and low mutation rates and of a tendency for microsatellites to cluster. From the human genome we generated a database of many thousands of (AC)(n) flanking sequences within which we searched for common characteristics. Sequences flanking microsatellites of similar length show remarkable levels of convergent evolution, indicating shared mutational biases. These biases extend 25-50 bases either side of the microsatellite and may therefore affect more than 30% of the entire genome. To explore the extent and absolute strength of these effects, we quantified the observed convergence. We also compared homologous human and chimpanzee loci to look for evidence of changes in mutation rate around microsatellites. Most models of DNA sequence evolution assume that mutations are independent and occur randomly. Allowances may be made for sites mutating at different rates and for general mutation biases such as the faster rate of transitions over transversions. Our analysis suggests that these models may be inadequate, in that proximity to even very short microsatellites may alter the rate and distribution of mutations that occur. The elevated local mutation rate combined with sequence convergence, both of which we find evidence for, also provide a possible resolution for the apparently contradictory inferences of mutation rates in microsatellite flanking sequences.
I brought this paper to Randman's attention in a previous thread in the context of the question of whether animals subject to similar selective pressures might not only exhibit convergent morphological changes but also convergent genetic changes.
This topic initiated in the
'Is convergent evolution evidence against common descent?' and subsequently invaded the
'Macroevolution: Its all around us...' threads.
There still seems to be quite a lot of ground to cover in terms of the exact implications of the Amos and Vowles paper and also in terms of the wider question of possible sources of convergence in DNA and the implications they might have on reconstructing phylogenies and our understanding of evolution in general.
Could people please try and stay on topic and discuss the literature on genetic or morphological convergence and the relationship between the two, Haeckel already has a thread of his own and any other issues belong in other threads of their own.
TTFN,
WK
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