Hi all, Some time ago, I had wondered how much genetic info from our ancestors were still with us today. I had guessed that "not much" was left of them in our genes. Now, it would seem that we have an answer from taf. See below John Carmi Parsons wrote: > > On 27 Jan 1999, DavidBotts wrote: > > > Here is an issue we Bottsfolk have that ties right into this whole issue of DNA > > testing. > > [snip] > > > 3) The Botts I am most concerned about making the list is elderly, and has > > outlived her brother and nephew, leaving no male representative in her line. > > > > 4) If we drew samples of DNA from the living, would have any shot of > > proving/disproving a proposed lineage between our female Botts and her > > suspected 1550-1620 male ancestor? > > It would be difficult to say the least, because women do not inherit the > paternal Y chromosome which is the necessary link in establishing father to > son descent (or son to father ascent). This is simply not a reasonable possibility. We are talking about something in the neighborhood of 10 generations, so the chance of any particular autosomal (non-X, -Y, or mtDNA) marker being inherited by both descendants is less than 1/1000. Since this is less than the distribution of most markers in the population, it is impossible to distiguish which shared markers derive from common descent, vs. which ones are simply coincidence. Since you need to perform analysis on several shared markers to reach statistically relevant results, you would have to look at well over 5000 markers to find 5 or so that are relevant. Needle - haystack. (That being said, if you want to pony up several hundred thousand dollars, I could give it a go.) > If she had surviving brothers or > fraternal nephews, their Y chromosomes could be compared with those of other > male Botts whom you know to be related; but since her brother and nephew are > deceased, that route is forever blocked (unless she has locks of their hair > --or her father's--that could supply the needed DNA). Even hair is problematic. The Y-chromosome screening methods I have seen used so far (Southern blot based RFLP analysis) require much more DNA than you would get from a hair. Most hair analysis has looked at mtDNA, for which there are as many as 1000 copies copies per cell, compared to one Y-chromosome. Likewise, most have used sequencing of PCR products to do the typing, and PCR can use sample sizes several thousand fold lower than RFLP studies. PCR of old tissue samples, such as hair, works best to determine the maternal lineage of a particular stiff when you know the type of the prospective mother. If you get lucky, you may be able to do a couple of RFLP tests to either disprove or support (but I doubt you could do enough tests to prove) the parents of an individual, but only if you have equally well preserved samples for both potential parents. The statistics on the Y chromosome are enough more stringent that I don't think you could get valid results. taf