‘Twissle Times’, March 2023
As Steve reported in ‘Twissle Times’ of June 2022, standard genealogy research has taken his arm of the Entwis(t)le family back 8 generations to John Entwisle, born in Ringley on 28 November 1736. John married Betty Ryle from Ringley, at Prestwich on 12 August 1755. To break through the ‘brick wall’ beyond John, he visited ‘Family Tree Live’ at Alexandra Palace in 2019, primarily to attend lectures on using DNA in genealogical research, and whilst there he provided a DNA sample to FamilyTreeDNA for testing.
Steve has since enrolled on an online Y-DNA course run by genetic genealogist, Diahan Southard, participating in her detailed DNA ancestry course over the winter. In the following 2 articles he reports back with the additional insight that these courses have undoubtedly provided.
How Y-DNA Helps Your Research
Most genealogists reach a ‘brick wall’ in their research at some point. Whilst the widely available autosomal DNA testing (e.g., that available from Ancestry) can often provide significant help, the nature of autosomal inheritance means that it is only of real value in identifying cousins that share common ancestors up to six generations back from the tester. However, other forms of DNA can provide significant help over much larger timescales.
Humans normally have 23 pairs of chromosomes; 22 pairs are known as autosomal, and 1 pair are the sex chromosomes – female sex chromosomes are denoted as X, and male as Y. Females have two X chromosomes, one each from their father and mother, but no Y chromosomes (XX). Males have the Y chromosome from their father, and an X chromosome from their mother (XY).
Many genes are unique to the Y chromosome and carry information necessary to develop a male foetus and for male fertility. Some genes, however, carry information for normal development in regions known as pseudo-autosomal, and are present on both X and Y chromosomes, so both males and females each have two functional copies.
Y-DNA has two types of markers which provide useful paternal ancestry information:
- STRs (short tandem repeats) markers
- are short sequences of DNA repeated along the chromosome; the number of repeats varies between individuals and is known as the individuals Y-DNA haplotype.
- have a similar (fast) mutation rate as autosomal DNA (approximately one mutation every 20 generations), making them useful for researching recent ancestry, but unlike autosomal, it provides information solely about the male (father-to-son) line.
- SNP (single nucleotide polymorphism) markers
- are single nucleotides (DNA building blocks).
- have an extremely slow mutation rate (approximately one mutation every few thousand years) making them useful to investigate ancient ancestry and determine an individual’s Y-DNA haplogroup.
Males who have the same or very similar STR marker profiles share the same paternal lineage, thereby allowing search for relatives along a paternal line over very many hundreds of years, i.e., for as far as documented records exist.
All that is required to confirm whether an individual is from a particular paternal lineage, is to test Y-STR markers at the lowest (and cheapest) level, known as Y-37.
FTDNA Y-37 results include:
- names of closest Y-STR matches to tester
- the predicted genetic distance of tester from closest matches
- family trees for matches (if uploaded)
- email address for matches
- testers standard Y-STR values (the number of repeats of the marker on the chromosome)
A standard international nomenclature is used for Y-STR markers so whilst Y-STR testing is not limited to one provider, FTDNA (Family Tree DNA) is the only company that provides ‘matches’, and the facility for Y-DNA (One Name) projects. An Entwistle Y-DNA Project has been set up and is open to all spelling variants, as well as those with different surname but share the same Y-STR DNA profile i.e., share the same patrilineal lineage.
Y-STR testing may also reveal that the male genetic line is not that of the current family name. There are several reasons why this may occur, to include the occurrence of a non-paternity event (NPE). The listing of close matches, ideally within a ‘Genetic Distance’ of 3 or less, at Y-37, are matches to ancestors that lived within a timeframe for which documented records could exist. Matches with different surnames may already be members of the appropriate Y-STR (One Name) Project and such projects should be checked. Contact with such matches may also perhaps provide even more valuable information than those of same surname as the tester.
Whilst the identification of Y-STR ‘matches’ may be useful, and review of associated family trees (if provided) may identify a common ancestor, this may often not be the case. But, joining the appropriate FTDNA Y-DNA project, allows comparison of an individual’s Y-STR Marker Profile with those of other anonymised members that may, or may not, be identified as matches, depending on genetic distance from tester.
As Y-STR (One Name) Projects grow in membership, groupings of close matches emerge. For each group a ‘Min’ (lowest Value), ‘Max’ (highest Values) and ‘Mode’ (most frequent Values) profile is automatically generated. The mode is regarded as the likely STR marker profile of the MRCA for members of the group.
In figure 2, simple examples of Y-STR grouping are provided. Two John Entwistles from the same vicinity and baptised in the same month, can often cause confusion and late nights, but Y-STR comparison reveals two distinct groups. Comparison of the two modes (most frequent value for each marker), however, suggests that the two groups share a distant common ancestor, separated by a total of 7 mutations.
By using a few simple rules, a genetic genealogy cladogram can then be created, as in figure 3. This is then translated into the most likely corresponding genetic family tree structure, as in figure 4. This immediately provides a structure which can be used to support genealogical research and resolve any confusion between members in the different John Entwistle groups.
This, however, isn’t the end of the story. The AP for John Entwistle of Stand has 7 marker differences i.e., mutations from that of John Entwistle of Prestwich, but there is sufficient similarity to suggest a distant common ancestor for both. This is when terminal SNP testing comes into play. Unlike STR markers which can undergo back mutations, terminal SNPs only ever occur one-time, making it possible to track back to genetic ‘Adam’. If just one member of each John Entwistle group takes the Big-Y 700 test, this should be sufficient to confirm whether the 2 John Entwistle groups share a common ancestor in a genealogical timeframe. FTDNA present the terminal SNP as a ‘Block Tree’, as shown in figure 5. Terminal SNPs mutate on average every 80 years (range 50-150 years), and the Block Tree indicates the number of mutations that there have been.
Figure 5 is the corresponding Block Tree for the fictional John Entwistles of Prestwich and Stand. The vertical column on the left denotes the number of terminal SNP mutations.
The Block Tree shown in Figure 5 shows that all members within each John Entwistle group share a common ancestor, and that the two John Entwistle groups themselves share a more distant common ancestor, 10 mutations back from current group members i.e., approximately 1220 BCE.
Returning to the individual John Entwistle groups, the STRs and SNPs combined provide irrefutable confirmation, or rejection, of shared common ancestors, the likely relationships within a family tree and the predicted timescale for MRCA’s. Additionally, terminal SNPs have the potential to answer the question about the origins of Entwistles i.e., where they were originally from.
More detailed explanations regarding SNPs, and STR’s, are for other articles!
[Stephen J Entwisle, member 120]