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A Y-STR is a short tandem repeat (STR) on the Y chromosome. Y-STRs are usually designated by DYS numbers. The standard Y-chromosome (Y-DNA) test used for genealogical purposes looks at differing numbers of Y-STRs, collloquially known as markers. The combination of Y-STRs tested is known as a haplotype.

Y-STR allele nomenclatures

Y-DYS conversions ca. 2011, Boed Marres

DNA testing companies or labs in certain cases use different nomenclatures to designate the same Y-STR allele. Thus, a conversion must be applied in these cases to accurately compare Y-STR results obtained from different companies. The most common nomenclature is based on guidance provided by NIST for Y-STR markers historically reported differently by various companies. The NIST standard is the proposal of ISOGG for genetic genealogy companies. [1][2]

  • from FTDNA to NIST: In FTDNA Projects the Haplotypes (STR Values) are formatted in the FTDNA lab standard (v1 until 2008, v2 since 2009?). For conversion from FTDNA v2 to NIST (ISOGG) standard used in scientific studies the following conversion apply:
    DYS441 +1, DYS442 +5, YGATAA10 +2, GATA H4.1 +1.
  • from NIST to FTDNA: DYS441 -1, DYS442 -5, YGATAA10 -2, GATA H4.1 -1. Sometimes DYS389II-I is listed; both values need to be summed.
  • from ISFG to FTDNA: same as for NIST except for GATA H4.1 -10 (-9-1)

For further details see the table of marker standards compiled by the Sorenson Molecular Genealogy Foundation (now preserved in the Wayback Machine)

See also the article by Diana Gale Matthiesen on Converting Y-DNA STR Test Results between SMGF, AncestryDNA, and FamilyTreeDNA

Y-DNA STR frequencies

NIST resources

Further reading

See also