FAQ
Please let me know if you have any other questions!
1. SNPs versus STRs
These are two different ways of analysing the DNA in the Y Chromosome
- - SNPs - this is a mutation at a specific place in the DNA. Once mutated, it is passed to all male descendants. These mutations occur at a slower rate than STRs. The BigY test looks at millions of locations for SNPs so can give very accurate information on how closely two men are relatedY-SNP Testing – Help | FamilyTreeDNA
- - STRs - areas where a DNA sequence is repeated multiple times. STR tests count the number of repeats. The larger the difference in number of repeats between two tests, the more time has passed since the two men shared an ancestor. These diverge more quickly than individual SNP mutations, so are useful in showing how closely related two men are in the relatively near past. The more STRs tested the more accurate the result.
2. What is the Y37 test?
The Y37 test looks at 37 STRs and calculates the 'Genetic Distance' - the overall difference between the STR scores on the test. So if all 37 STRs are the same, the GD is 0. If there is one mutation, it is 1 etc (it gets more complicated but I don't fully understand that yet!)
As an indication, for the Y37 test, the following Genetic Distances imply rough relationships as follows:
- GD=0 - c1800 CE (1600 - 1950) (i.e. about 1800 AD but could be between 1600 and 1950)
- GD=1 - c1750 CE (1450 - 1900)
- GD=2 - c1650 CE (1250 - 1850)
- GD=3 - c1500 CE (1000 - 1800)
- GD=4 - c1300 CE (650 - 1750)
3. When will I get my results?
(Sept 2023) - Current processing times after receipt of sample are 5-7 weeks.
4. What do my results mean?
The FamilyTreeDNA helpsite has loads of helpful materials to help you on this, and please ask here as well!
5. Where do we go for more information?
Interpreting the test results can get very scientific - I am learning fast but am certainly no expert.
- There are lots of helpful tools on FamilyTreeDNA's website
- There are helpful and active communities of Y-DNA specialists on Facebook and FamilyTreeDNA - consider joining other projects too, such as a wider project for your earlier haplogroups.
- Ask me if you have any questions and I will help you get the answers!
6. What if I don't match the other testers?
There are a few reasons why this might be:
- Our branches of the Girdlestone family aren't in fact related, and/or
- There has been a 'NonPaternity Event' in one of our ancestry lines - where the Y-DNA has split from the 'Girdlestone' surname - for example the surname was passed from mother (or step-father) to son at one point, or there was an adoption, etc. You can see a full list here: https://isogg.org/wiki/Non-paternity_event#NPE_scenarios_in_the_context_of_genetic_genealogy
The YDNA tests show how your direct male ancestors migrated around the world many thousands of years ago, all the way back to 'Y-Adam' - the man from whom all men alive today are descended in the direct male line. He was not the only male alive at that time but is the only male whose line has still survived to the present day. He is currently estimated to have lived between 237,000 and 581,000 years ago. After your upgrade to BigY you'll get even more detailed information about the path of your male ancestors.
8. What do we know about the Girdlestone family?
Four main branches of the family have been documented, with many other branches which can't be attached to those with certainty so may form their own branches. The main ones I know of are:
- Kelling - founded by the father of three brothers, who were born around 1570
- Wramplingham - founded by Willemus Girdlestone, born around 1616 and lived in Great Walsingham
- Walsingham - headed by John Girdlestone (1755 - 1838) - his parentage is uncertain
- Burnham Westgate - founded by Zurishaddai Girdlestone (bc 1750) Married in Little Walsingham.