DNA and genealogy

 DNA can help solve genealogical puzzles, but there are many subtleties. Thus a child generally acquires 50% of its DNA from each parent, thus in effect discarding 50% of each parent's DNA. After a few generations it becomes increasingly likely that all of a parents' DNA will have been discarded in that family line. That is, eventually, even though one knows of a direct ancestor, none of that ancestors' DNA may appear in one's own DNA! This observation does not of course apply in the case of mitochondrial DNA which is transmitted through the female line, and Y-chromosome DNA which is transmitted through the male line.

Julian Land has had his autosomal DNA measured and the 'assigned kit number' from ancestry.com is TF4905650; his initial reaction to the ethnicity revealed by ancestry.com may be found here. Close Land and Truscott relatives became immediately apparent. When the data was uploaded to Family Tree DNA the kit number given there was B558301. There was an immediate reaction to this upload - Geoff Congdon got in touch - he is a 2nd cousin and descends from Edmund Truscott #1479, youngest brother of Mary Truscott, Julian Land's maternal grandmother (ref 307). Julian Land's Y-haplogroup is I-M253, the distribution of which shows a Danish origin some 5,000 years ago, but whether it came to England in the Land case in earlier (Saxon) or in later (Viking) times is currently unknown, and is a topic of current interest for his genetic matches! Julian Land's mitochondrial haplogroup is H69, which appears to have originated in the Caucasus some 25,000 years ago, and is one of the 7 common European haplotypes. How it got to Cornwall to produce the Truscott/Best/Trewthewey line is unknown, but there are surprisingly few genetic matches and it may be possible to find out more of this story.

Notwithstanding many complications, DNA and its implications for genealogy is an active field of enquiry, and interesting findings have been made. In a recent study a promising genetic signature of Sephardic Jews is examined (ref 305). An earlier result is cited - from which it emerges that the Ashkenasim, which comprise the largest Jewish population worldwide, shows a prominent founder effect with only 4 mitochondrial haplotypes comprising 40% of the modern population and with the most frequent haplotype found in 19% of individuals. Sephardim, descendents from Spanish and Portuguese Jews who were the largest Jewish population until the 18th century, instead show a large variation in maternal founders of the communities of the Ottoman Empire. This was especially apparent in their results for Turkey, with the 4 most frequent haplotypes found in only 17% of the present day descendent population and the most frequent haplotype found in not quite 6% (for Bulgaria, the numbers are 27 and 8.5%, respectively). The Ottoman Empire, including Turkey and Bulgaria, received many of the Jewish people who were exiled from Spain and Portugal in the late 15th century. The contrasting findings for the two prominent Jewish populations suggest a greater genetic diversity in mitochondrial DNA in Sephardim than in Ashkenasim. However it is noted that the seemingly higher genetic variability in the present-day Sephardic population does not preclude uncovering Sephardic signatures, the object of the study.

Our notes on DNA as it relates to Barrow Lousada genealogy may be found here.