Re: DNA testing

In article <L-mdnX0gc9Why7bVnZ2dneKdnZydnZ2d@xxxxxxxxx>,
Ian Goddard <goddai01@xxxxxxxxxxxxx> wrote:
I'm afraid I have a bit of a problem with mtDNA and it's this:

The Y chromosome exists in only a single copy per cell (OK, zero copies
in females). The mtDNA chromosome exists in multiple copies. What's
more we eukaryotes have been carrying mitochondria round in our
cytoplasm since the precambrian. Given the amount of mutation that must
have occurred in that time one might reasonable expect that any host
cell line would carry a number of distinctly different mitochondrial
lines.

Interesting speculation. I'm sure that cannot be so - or the tests wouldn't
work - but I don't know why.

If this were the case, however, ISTM that mtDNA typing would be
far less practical than Y-DNA typing as one would always be looking at a
mixture of different chromosomes. As mtDNA typing is practical,
however, there must be some mechanism constraining the mitochondria of
host cell lines to a single mitochondrian line. What is this mechanism
and what is its possible impact on the restricted diversity seen in
host-to-host mtDNA comparisons?

Good question, and you have succeeded in annoying me because I didn't think of
that question! ;-) I don't know. Must ask.

Actually I have 2 problems. The other is the one I posed in my previous
post. John says the few (whatever the number) ancestor argument is a
"claim", you say it's a "well accepted idea". Nobody seems to be saying
it's a "hypothesis" and offering testable predictions. Can anyone give
me a reasonable heads-up, say a recent review article, in a refereed
journal that I might find in my local University library; Nature or
Science would be ideal?

You'll need to search back a touch. Try starting with:

The Human Y Chromosome: An Evolutionary Marker Comes of Age
Jobling & Tyler-Smith, Nature, August 2003 p598ff

Find the diagrams showing the T and mt DNA distribution maps by J D McDonald

The genetic Legacy of Palaeolithic Homo sapiens sapiens in Extant Europeans: a
Y Chromosome Perspective
Ornella Semino, et al, Science, 10 november 2000 (www.sciencemag.org)

A Y Chromosome Census of the British Isles
Capelli, et al, Current Biology, May 27 2003

Mitochondrial genome variation and the Origin of Modern humans
Ingman et al, (letter) Nature, 7 Dec 2000

Origin, Diffusion, and Differentiation of Y-Chromosome Haplogroups E and J:
Inferences on the Neolithization of Europe and Later Migratory Events in the
Mediterranean Area
Semino, et al American Journal of Human Genetics, 2004 74:1023-1034

Population Structure in the Mediterranean Basin: a Y Chromosome Perspective
Capelli, et al Annals of Human Genetics 2005

High-resolution Phylogenetic Analysis of Southeastern Europe Traces Major
Episodes of Paternal Gene Flow Among Slav Populations
Pericic & Lauc, et al OUP for Society for Molecular Biology and Evolution

I have taken the above sample from papers that I know have been available
on-line over the past 2 or 3 years. They may not answer your question directly
but their references should give a clue for further investigation.

The formal academic papers show investigations that lag behind those conducted
by amateurs. Data available to informal groups - see links at Family Tree DNA
as one possible starting point - is of higher quality (more markers though
there is a health warning over its non-random nature) than that available to
professional researchers. This is because development in testing techniques is
moving so fast. Small areas of research - looking at just one or two
haplogroups - is going on all over the place and most people are simply
waiting for more research data to come in. One that I know of is looking for
information about J2e1 and E3b haplogroup data as the distribution across the
UK may conform with the hypothesis that those groups originated with the
Sarmatians imported by the Romans in the second century. More data may
differentiate between competing hypotheses but I'm waiting for DNA from a body
in Ribchester buried with a dragon standard - and matching my profile!! ;-))

There is much good work going on - don't stick to the formal papers - and
perhaps have a look at the genealogy DNA list. Send an e-mail to
GENEALOGY-DNA-request@xxxxxxxxxxxx with subscribe in the subject line and body
of the message.

--
John
.

Relevant Pages

  • Re: Dating with DNA? Problems and Current Approaches
    ... First is the use of STR variances. ... For the Y chromosome and some autosomal markers the ... sites (on the DNA that is, not places on the planet.) Some ... except possibly for human mtDNA, ...
    (sci.archaeology)
  • Re: Why dont mitochondria have junk DNA?
    ... DNA being passed exclusively down the female line. ... So the Y chromosome should have no junk? ... It is fairly well established that mitochondria are ...
    (talk.origins)
  • Re: DNA testing
    ... As mtDNA typing is practical, however, there must be some mechanism constraining the mitochondria of host cell lines to a single mitochondrian line. ... All this theory depends on a set of assumptions - the nature of mtDNA genetics, assumptions about constancy of rates of genetic change and their use as dating mechanisms, ... The Human Y Chromosome: An Evolutionary Marker Comes of Age ...
    (soc.genealogy.britain)
  • Re: Asians have hijacked Japanese study
    ... > pair up with the 23 chromosome in Mommy's egg. ... and each of those mitochondria has its own DNA. ... Based on the DNA in the original ones. ...
    (sci.lang.japan)
  • Re: Mitochondrial degeneration?
    ... "The rate of mutation in mtDNA is calculated to be about ten times ... greater than that of nuclear DNA, possibly due to a paucity of DNA ... functional Mitochondria, ...
    (talk.origins)
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