The Trezise DNA Project started in 2008 with sixteen (16) subjects who underwent cheek swabbing as well as a family tree analysis. All persons had surname spellings Trezise, Tresise, Tresize, Trezies and had family trees with data springing from the 1600s that had been compiled using Parish records, wills, the census and latterly certificates.

A 67-marker Y-STR BATWING test1 indicated they were possibly all related so basic Y-SNP testing of the Y chromosome was undertaken. All samples were part of the R1b-Z16943 branch of the world-wide Y DNA haplogroup tree and remarkably it appeared that more than half of the STR profiles could be mapped to an area within Cornwall. It was hypothesised that deeper SNP profiles would be an even better way to map back to Cornwall.

The advent of the Big Y-700 from Family Tree DNA in 2019 gave an opportunity to test the hypothesis so twenty five (25) subjects with the Trezise surname or one of its variants was chosen for the study. This testing revealed that the Trezise family derived from a single male who moved into Cornwall probably from Devon and that SNPs can be used to document family lines for males living outside Cornwall.

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