Decoding Our DNA: The Basics of DNA and Genetic Testing

The Basics

At the heart of genetics lies DNA, or deoxyribonucleic acid, a molecule that serves as the instruction manual for building and maintaining our bodies. Think of our entire genome as a library that contains all our genetic material. In this library, chromosomes are the books, and DNA is the text inside these books. The DNA is divided into chapters called genes which carry a specific set of instructions for the body. Just as the same 26 letters can be used to write different kinds of books, our DNA uses four “letters”, or nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C).[ref 1,2] These nucleotides are arranged in specific sequences, similar to words in a book, and their order dictates the instructions for building proteins. Proteins, in turn, perform essential functions in the body, from building muscles to aiding digestion and determining how medications are processed.[ref 3] So, to break it down, nucleotides form DNA, which are organized into genes and neatly stored as chromosomes. The instructions in these genes tell our bodies how to make proteins, which carry out necessary tasks in our bodies.  

Although we all have unique DNA, more than 99.9% of our DNA is the same for everyone. [ref 4] This is because our bodies need to follow the same general instructions to function properly.  However, it's that small percentage that makes us different. Some of this is as easy to see as the color of our hair and eyes, but it is also why some people can eat certain foods without problems, while others may have allergies or sensitivities and why a medication may work for one person, but not for another. [ref 3,4]  

SNPs

Single Nucleotide Polymorphisms, or SNPs, are the most common type of genetic variation among people. They occur when a single nucleotide (one of the four building blocks of DNA: A, T, C, or G) is replaced with another nucleotide in a DNA sequence. [ref 5] Think of SNPs as a tiny spelling change in a word, where one letter is swapped for another - they usually don't change the meaning by much, but sometimes they can. For example, a SNP might slightly change the shape of a protein, affecting how it works. When you do genetic testing, we look at common and impactful SNPs and use research on these SNPs to help you understand how they influence your traits and health. [ref 6,7] 

A few facts about SNPs:  

• For a change in a DNA sequence to be classified as a SNP, it must be present in at least 1% of the general population. [ref 8] 

• SNPs are not the same as disease-causing mutations, which are much rarer and often have more serious consequences. [ref 8]  

• SNPs occur roughly every 300 nucleotide base pairs throughout the human genome, resulting in about 10 million SNPs in a person's DNA! [ref 4] 

Lastly, while the sequence of your DNA doesn’t change throughout your life, how your body uses the information can change. You might hear people talk about turning genes "on" or "off." This means that certain environmental factors—like your diet, exercise, or exposure to stress—can affect which parts of your DNA are active, without changing the DNA sequence itself. This field of study is called epigenetics, and it helps explain how lifestyle choices or environmental factors can impact your health by influencing gene expression. [ref 9] Certain SNPs can further influence how our environment impacts gene expression. The connection between genetic predispositions (SNPs) and environmental influences (epigenetics) adds another layer of complexity to personalized medicine and lifestyle recommendations.  

Interested in learning how your SNPs influence your lifestyle or medications? Contact us so we can discuss which of our affordable panel(s) meets your needs! 

For a better understanding of the scientific lingo surrounding genetics- check out our Glossary.

References

1. Centers for Disease Control and Prevention. Genomics and Health: About. Available from: https://www.cdc.gov/genomics-and-health/about/index.html.  

2. Sadee W, Wang D, Hartmann K, Toland AE. Pharmacogenomics: Driving Personalized Medicine. Pharmacol Rev. 2023;75(4):789-814. doi:10.1124/pharmrev.122.000810 

3. National Human Genome Research Institute. Genetics vs Genomics Fact Sheet. National Human Genome Research Institute. Updated July 14, 2023. Accessed October 3, 2024. https://www.genome.gov/about-genomics/fact-sheets/Genetics-vs-Genomics 

4. Nelson MR, Marnellos G, Kammerer S, et al. Large-scale validation of single nucleotide polymorphisms in gene regions. Genome Res. 2004;14(8):1664-1668. doi:10.1101/gr.2421604 

5. National Center for Biotechnology Information. Understanding Human Genetic Variation. Biological Sciences Curriculum Study. National Institutes of Health; 2008. Available from: https://www.ncbi.nlm.nih.gov/books/NBK20363/. 

6. Shastry, B.S. SNPs in disease gene mapping, medicinal drug development and evolution. J Hum Genet 52, 871–880 (2007). https://doi.org/10.1007/s10038-007-0200-z 

7. Shatoff E, Bundschuh R. Single nucleotide polymorphisms affect RNA-protein interactions at a distance through modulation of RNA secondary structures. PLoS Comput Biol. 2020;16(5):e1007852. Published 2020 May 7. doi:10.1371/journal.pcbi.1007852 

8. Karki R, Pandya D, Elston RC, Ferlini C. Defining "mutation" and "polymorphism" in the era of personal genomics. BMC Med Genomics. 2015;8:37. Published 2015 Jul 15. doi:10.1186/s12920-015-0115-z 

9. Zaina S, Pérez-Luque EL, Lund G. Genetics talks to epigenetics? The interplay between sequence variants and chromatin structure. Curr Genomics. 2010;11(5):359-367. doi:10.2174/138920210791616662