What in the world is a SNP??

A SNP (pronounced “snip”) is a single nucleotide polymorphism to be exact. Ok, that doesn’t help at all, right? A basic overview on genetics is necessary to really understand SNPs. For simplicity, these are the key pieces:

  • Your genetic code is built with DNA.
  • The smallest building blocks of DNA are called nucleotides.
  • A nucleotide contains a base attached to a sugar molecule and a phosphate molecule.
  • There are four bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
  • These bases come together as pairs:
  • Adenine and guanine, AG
  • Cytosine and Thymine, CT
  • The order of the bases what is referred to as the sequence. The sequence is like our genetic alphabet.
  • The nucleotides run along two strands, that come together to form the familiar double helix of DNA.


As humans, about 99% of our genetic code is the same. The most common variation that makes all of us different is a SNP. This is where one nucleotide is replaced with another like adenine (A) is replaced with guanine (G). Usually the SNPs occur along a sequence of DNA, between sections that code for a gene, and this is not thought to have any health consequences. It is when the SNP occurs in a gene that we may see impacts on human health.


The most commonly known SNP you may have heard of are the SNPs that occur in the MTHFR (methyltetrahydrofolate reductase)gene which affect the activity of the enzyme. These SNPs determine how well folic acid is converted to methylfolate. People will take L-5-MTHF (L-5-methyltetrahydrofolate) in supplement form as a result and there are even prescription medications.

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