Understanding Ftdna Y-STRs advanced tests

[keyhook]

I'm new in this and I would like to know what the advanced STR tests offered by Ftdn are for.

Do they help only in case of close Y matches to confirm or there is something else one can learn?

Test Type Marker
Y-STR DYF371X
Y-STR DYS385a/b (K)
Y-STR DYS464X

Thank you and a great weekend to everyone

[DRNewcomb]

Since no one else has said anything, I'll grace you with what little I know on the subject. Two things are tested in Y-DNA: SNPs and STRs. The SNPs are used to determine your Y-haplogroup. There is a standard test for SNPs which should get you into a haplogroup and there are advanced tests that add more SNPs to be more precise.

STRs are handy in Y and mitochondrial DNA because these don't undergo recombination. A change of STR from father to son (Y-DNA) or mother to child (mtDNA) represents a mutation which will be passed on to the next generation unchanged, unless there is another mutation. STRs are tested in standard "panels". Each panel adds some more STRs. The more STRs that are tested, the more precise one can be about the relationship between two individuals, provided they both tested to the same level.

If you don't have any reasonable matches at a lower STR testing level (e.g. 25) adding more (e.g. 111) should not add more matches. There is one exception and that is if the other person limited his matches to a high level (e.g. only matching people who are matches at Y-111). This kind of idiotic behavior will restrict matches to only people who took the highest and most expensive level of Y-DNA test and who also match you.

Generally, you count the differences between your STRs and the other person's STRs to calculate "genetic distance". Then you apply some rule-of-thumb math to guess how many generations or centuries ago you shared a common ancestor.

And if I'm completely out in left field here, I'll be happy if someone provides a little gentle correction.

[Jim Barrett]

mtDNA

From https://isogg.org/wiki/Mitochondrial_DNA_tests

mtDNA by current conventions is divided into three regions. They are the coding region (00577-16023) and two hyper-variable regions (HVR1 [16024-16569], and HVR2 [00001-00576]). All test results are compared to the mtDNA of a European in haplogroup H2a2a. This early sample is known as the Cambridge Reference Sequence (CRS). An updated reference sequence was subsequently published and samples are now compared to the revised Cambridge Reference Sequence (rCRS). A list of single-nucleotide polymorphisms (SNPs) is returned. The relatively few "mutations" or "transitions" that are found are then reported simply as differences from the CRS, such as in the examples just below.

Bolding is mine. mtDNA tests SNPs, not STRs. Please follow the link to see the examples.

[spruithean]

I'm new in this and I would like to know what the advanced STR tests offered by Ftdn are for.

Do they help only in case of close Y matches to confirm or there is something else one can learn?

Test Type Marker
Y-STR DYF371X
Y-STR DYS385a/b (K)
Y-STR DYS464X

Thank you and a great weekend to everyone

Those STRs are really only useful if recommended by a project administrator for various reasons, especially if a certain family group has specific STRs, or extra repeats at DYS464a,b,c,d (adding e,f,g, etc). Or if there is a null value on one of those markers that again, is unique to a family.