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Hi Smitty,?

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Exact duplications of normally single-copy Y-STRs will generally not show up in the Family Tree DNA system due to the methods of testing. They must initially occur, and then mutate to different alleles (values). Any Y-STR can potentially be duplicated in this manner, and the Y chromosome as a whole is prone to repeats and duplications, some of which become embedded in the genome over the course of millennia.

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DYS19 is located just before the centromere on the shorter Yp arm of the Y chromosome (hg38 co-ordinates chrY:9,684,325..9,684,519). This region is largely unique, meaning it's easily extracted in tests, but it does contain some duplications of other parts of the Y chromosome (inverted repeats). DYS19 is not on one of these repeats, which is why it normally takes a single value. DYS19 is not often null, so it is generally more stable against large scale deletions than some nearby STRs. However, it is not often duplicated either. What you are seeing in this test is a fairly rare occurrence in this particular region of the genetic code, but it does look like a segment of his Y chromosome has been duplicated, and the DYS19 STR in either the original or duplication has mutated to gain an extra three repeats.

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Depending on the size of the duplicated region, he may have duplications of other nearby Y-STRs, e.g. DYS487, DYS616, DYF403S1a (two duplications of this already bracket DYS19), DYS521 and DYS615. These duplications may be invisible if they retain the same alleles as each other.

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Cheers,

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Iain.