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Getting SNP’y with DNA

The Legal Genealogist is on the road, so the blog during this extended trip is featuring terms we all need to understand and use as genealogists.

Today’s term, for DNA Sunday, is SNP.

Pronounced “snip.”

Dna-SNPIt’s an acronym, short for Single Nucleotide Polymorphism.

Which, all in all, is such a mouthful that it’s no wonder it got shortened to SNP.

By definition, it’s “a DNA sequence variation occurring when a single nucleotide adenine (A), thymine (T), cytosine (C), or guanine (G]) in the genome (or other shared sequence) differs between members of a species or paired chromosomes in an individual.”1


That helps a lot, doesn’t it? (She says, with tongue in cheek and a huge dose of sarcasm.)

Think of it this way: a SNP is “a change in your DNA code at a specific point.”2 And we look at those changes to “confirm haplogroup assignments, to learn more about … deep ancestry and to rule out false positive matches” with possible cousins.3

So SNPs help us figure out exactly where we belong — on what branch of the human family tree — and who else ought to be hanging out on that branch with us.


Something to get snippy about, for sure.


Image: SNP model by David Eccles, CC BY 4.0

  1. ISOGG Wiki (, “Single-nucleotide polymorphism,” rev. 5 Apr 2015.
  2. “Glossary: Single Nucleotide Polymorphism (SNP),” Learning Center, Family Tree DNA ( : accessed 6 June 2015).
  3. ISOGG Wiki (, “SNP testing,” rev. 8 May 2015.
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