Definition of YDNA terms

[dbeezley]

I'm working on some basic genealogical DNA information (YDNA) with examples specific to our surname study. I want to be sure I'm using terms and concepts correctly.

The definition of Haplotype in the FTDNA glossary is:

Haplotype - A haplotype is the set of values for a set of DNA values. For example, the results of the Y-DNA12 test for one person is their haplotype. Two individuals that match exactly on all markers have the same haplotype.

I have been saying that two men are of the same Haplotype if the STR match is in the appropriate range (e.g. no more than GD7 of 67 markers). It is true that I consider GD3 a better range. If lineages are considered to be the "same haplotype" if a perfect match, what do we call those lineages that are -1, -2, -3, or more? Most YDNA Projects list participants in Lineage Groups often referred to as "Group 1", "Group 2", etc. Using the term "Groups" can get people confused with Haplogroups. In the Beasley Study, I have been referring to them as "Clans" using color names matching the color headers in the FTDNA chart. I know that is non-standard. Is there a term for profiles that are near but not perfect?

[JSW]

For my surname projects I use the term "family" as they all have the same surname. I can see the term group or clan as on could use for a Haplotype or a SNP project.

[Jim Barrett]

Two men have the same Haplotype ONLY when they are a genetic distance of zero. An exact match is required before you can say they have the same Haplotype. You can say they have SIMILAR Haplotypes if they have a low genetic distance.

[clintonslayton76]

Addendum

Men can be grouped into separate Haplogroups. I group by the oldest ancestor if known or suspected, or the region where the family is first found if this is unclear. This can be confusing if you do not remember that terminal SNPS from Big Y can artificially make a man look different from his fellow group members. EXAMPLE: I am I-F1997, but that is a refinement, I am still within I-M253.

I would add that the genetic distances are misleading with any markers less than 67, and my cousin with 111 markers shows a distance from me of 3 even though we cannot share a male common ancestor less than 7 gens back. If the YDNA is very stable, the distances are underestimated, no matter how high the markers. There is no such thing as an "average" mutation rate, that is a fiction.
See the Slaton YDNA Project for the "Carolina" group, men whose ancestors lived 1771-1830, but the descendants look more like 1st and 2nd cousins.