snip
We do indeed inherit exactly 50% of our DNA from each parent, because we inherit one of each chromosome pair from each. And that inevitably means that we inherit half of each of their DNA.
The only exception to this is the 23rd chromosome, which determines gender. The X chromosome, which both genders have is larger than the Y chromosome which only men have, so a man inherits a longer length of DNA in the 23rd chromosome from his mother than his father. But that fact isn't significant to what we are discussing here.
Eric you seem to know more than Rolf Kohl, Dr.rer.nat. (Ph.D) Ecology & Biology, Ludwig Maximilian University of Munich, for instance, who states-
“child inherits EXACTLY 50% of the chromosomes from each of both parents. All mitochondrial genes are inherited only from the mother.
Thus a child receives only close to half of the genes from the father and a little bit more than half of the genes from the mother.”
We inherit approximately (but not exactly) 25% from each of our 4 grandparents (i.e. 2 generations back), approx 12.5% from 3 generations back, approx 6.25% from 4 generations back, approx 3.12% from 5 generations back, etc. The further back we go, the smaller the percentage and the greater the potential for variation.
Which is what I was saying due to DNA dropout (this is where the DNA of a particular ancestor is not passed down to a child, that particular DNA may be passed on to a sibling but the child’s descendants will never carry the “missing” DNA.
I can only conclude that you have taken an unnecessarily sceptical and not fully accurate view of DNA testing. I hope you find the links I have given helpful in building your understanding, as they have helped me. Thanks.
Far from “taking an unnecessarily sceptical and not fully accurate view of DNA testing” I have carried out in depth study of many hundreds of scientific evaluations of DNA over the last 17 or so years. I approached the subject hoping it could prove to be a very useful genealogical tool, but my conclusions are the current offerings contain more hype and miss information than useful data.
The Ancestry offerings are at present going to produce hundreds if not thousands more inaccurate Ancestry trees due to the many false positives that the naive are going to cling onto to “prove” their inaccurate trees.
As I have said in the past when the science develops it may prove to be of use in genealogy but at present it is far too inaccurate and too expensive to be of any use to the bulk of genealogists.
That is not to say it cannot be used as an additional tool by careful researchers who have a well researched lineage but for the customer base the adverts are targeting it is as useful as a pin and a telephone directory
Cheers
Guy