[Varda]

About the tomb of the unknown, That is too cool. About DNA, Thanks for offering to answer a question. At my level of learning I try to read the journals as best I can. Its the abbreviations and jargon I find difficult. I try to stay out of the nuts and bolts of the chemistry. Do you think selection studies and/or epigenetics will pose a threat to these mtDNA derived migration theories?

[allmendream]

Not at all. I don't believe the same epigenetic mechanism of methylating DNA to shut it down is active in mitochondria (would have to look it up); but even if it did it wouldn't change how it was inherited or its inherent mutation rate. Epigenetics is just another level of control, it packages DNA that is not actively being used into histone coils; the interesting thing about epigentics (to me)is how moms and dads change the methylation pattern of the DNA they pass down to enhance their own particular reproductive strategies.

[allmendream]

I looked it up. It does seem that vertebrates do methylate their mitochondrial DNA and this would increase its mutation rate. Invertebrate and plants and fungi do not methylate their mitochondrial or chloroplast (in plants)DNA.

http://www.ncbi.nlm.nih.gov/pubmed/3252156?dopt=Abstract

From nucleotide sequences of mitochondrial and chloroplast genes the probable frequency of the CpG——TpG + CpA substitutions was determined. These substitutions may indicate the level of prior DNA methylation. It was found that the level of this methylation is significantly lower in mitochondrial DNA (mtDNA) and chloroplast DNA (chDNA) than in nuclear DNA (nDNA) of the same species. The species (taxon) specificity of mtDNA and chDNA methylation was revealed. A correlation was found between the level of CpG methylation in nDNA, and mtDNA and chDNA in different organisms. It is shown that cytosine residues in CpG were not subjected to significant methylation in the fungi and invertebrate mtDNA and also in the algae chDNA. In contrast, the vertebrate mtDNA bears the impress of CpG-supression, which is confirmed by direct data on methylation of these DNA. Here the first data on the possible enzymatic methylation of the plant mtDNA and chDNA were obtained. It was shown that the degree of CpG-suppression in the 5S rRNA nuclear genes of lower and higher plants is significantly higher in the chloroplast genes of 4,5S and 5S rRNA. From data on pea chDNA hydrolysis with MspI and HpaII it was established that in CCGG sequences this DNA is not methylated. The role of DNA methylation in increasing the mutation rate and in accelerating the evolutionary rates of vertebrate mtDNA is discussed.