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Single Nucleotide Polymorphism (SNP)

What is a single nucleotide polymorphism (SNP)? 

Single nucleotide polymorphisms (SNPs) are changes at one nucleotide subunit of DNA. To be considered an SNP, the change must be present among at least 1% of people in at least one population. Nucleotides include the base pairs adenine (A), thymine (T), cytosine (C), and guanine (G). If at a given DNA location, there is a difference in base pairs among at least 1% of the population (for example a C (cytosine) replaces a T (thymine) this change at this specific location would be considered a SNP. The SNP that is more common among a given group of people is called the major allele and the one that is less common is called the minor allele.

What is the function of a single nucleotide polymorphism (SNP)? 

Single nucleotide polymorphisms are the basis of uniqueness among individuals. Just a simple exchange of one nucleotide for another can result in a big change metabolically. More specifically, a single nucleotide polymorphism can change the amino acid structure of the encoded protein. Changing the amino acid structure can disrupt the folding of a protein leading to a dysfunction in the protein product. For example, the VDR gene codes for a vitamin D receptor in our cells which helps us absorb vitamin D. If an individual has a SNP in the VDR gene, it could lead to impaired absorption of vitamin D. This would warrant specific nutrition intervention such as increasing consumption of foods high in vitamin D or initiation of a high dose vitamin D supplement. 

How are SNPs detected? 

Thanks to advances in technology, an individual’s DNA can be easily collected and analyzed for SNPs. Each of our cells have a nucleus, which contains a full complement of an individual’s genetic material. This contains all the information needed to analyze DNA. Therefore, DNA can be collected with a simple swab of the cheek to collect cells in the form of secretions. In a laboratory, the genetic information in the nucleus of the cells collected can be extracted and amplified. Usually, specific probe sequences with fluorescent dye attached are used to identify whether the DNA sample contains a particular SNP.


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