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What is a SNP?

Before we can answer this important question, let’s take a step back and look at DNA. DNA, or deoxyribonucleic acid, is the genetic code that determines all the characteristics of a living thing. On average, humans share at least 99.5% of their genome sequence, but we are all genetically unique.

The information in DNA is stored as a linear code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. Sequences of bases along the DNA molecule comprise genes, and these genes in turn provide directions to make proteins. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

SNPs, or Single Nucleotide Polymorphisms (pronounced snips), are single base changes within genes, akin to single letter spelling variations. (Think analyse vs analyze.) It is important to emphasize that these are variations, NOT mutations. SNPs represent 90+% of the total variation amongst individuals, meaning that nearly every genetic difference you encounter on a daily basis is caused by single nucleotide changes in various genes. These tiny variations (SNPs) may slightly change the function of the protein encoded by the corresponding gene.

As DNA is structured as a double helix molecule, we have two versions of each gene - one received from our mother and one received from our father. Hence we also have 2 versions of each SNP. If they are the same letter, you are homozygous for that SNP and are likely to see a greater effect of that particular genetic trait. If you have two different letters, you are heterozygous and likely to see a smaller effect of the SNP.

Depending on the SNP, there might be a benefit, a neutral effect, or a higher risk of a disease state or reaction to a drug or toxin in the environment. Most SNPs came about to offer adaptive benefits. Some may protect from certain environmental conditions but at the same time increase the risk of specific health concerns in other environments.

In some cases, we do not know which SNP is the ancestral (original) version and which are changed versions. SNPs are passed on from one generation to the next, and rarely change. Your reported SNPs will look something like this, CYP1A2-rs762551 (A;A), indicating the name of the gene, the SNP or rs number, and what versions you inherited. This person has two A’s at this SNP (one from mom and one from dad). Incidentally, if you have two copies of A at this SNP, you are a fast caffeine metabolizer.

This is an exciting time in Nutrigenomics research with new studies revealing the benefits and risks of these genetic variations. Many SNPs related to nutrition and fitness have been identified and new evidence continues to emerge. Nutrigenetics Specialists offers testing and counseling to help you determine the best diet and activity plan based on your unique individual SNPs. We use tools that look at the most researched and valuable SNPs, and as dietitians can help you translate the science into everyday action to get results!

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