While everyone's DNA uses the same four letters (A, T, C, and G), to make the same genes, there can be differences in our genes, called genetic variants.
Some genetic variants affect how a person looks. For example, one person has a variant that tells their body that they will have blonde hair. Another person will have a different variant that will cause that person to have brown hair. While each person has minor differences in the letters that make up a gene, we all have the gene (basic set of instructions) that determines our hair color.
Types of Genetic Variants: SNPs & CNVs
Genetic variants can also be thought of as typos in the spelling of the genetic code. A change in a single letter may change the codon, or "word" that is spelled out. This change may have no effect or it may change the amino acid and the protein. These single letter changes are called single nucleotide polymorphisms, or SNPs (pronounced "snips").
Some SNPs can increase a person's risk for disease. In this example, the fifth codon (CTT) codes for the amino acid leucine in the "Average Risk Individual." In the" Increased Risk Individual," the A in the fifth codon has been changed to a G. The codon GTT codes for a different amino acid, called valine. This change results in an increased risk for heart disease.
Other times a word can accidently repeat itself. This change is called a copy number variant, or CNV, because it is a variation in the number of times a particular letter or string of letters appears in the genetic code.
Both SNPs and CNVs in the genetic code can change the protein — or amino acid chain — that is made. Any change in the protein can affect how people look, how well medicine works for them, and how likely people are to develop diseases like cancer, diabetes, and heart disease.
Risk Variants and Protective Variants
Some genetic variants, called risk variants, can increase your risk for developing a disease. For example, if a person has a genetic variant called rs1333049, they are at higher risk for developing coronary artery disease than people who do not have this variant. Other genetic variants can decrease your risk for developing a certain disease. These variants are called protective variants. For example, if a person has protective variant called rs9272346, they have a lower risk of type 1 diabetes than people who do not have this protective variant.
In the example below, the change from C to G in the genetic code gives Steven an increased risk for an early heart attack. This is not a diagnosis, nor is it Steven's total genetic risk, but it is one piece of the puzzle and gives him an increased risk for the disease because of his genetics.
Just like a change in the genetic code can affect your disease risk or how you look, some SNPs influence how an individual will respond to prescription medications. Genetics can determine if you will respond to the typical dose of a medication or if you need a higher or lower dose, or even an alternative medication. The practice of using genetic information for clinical care, managing disease and tailoring therapeutics, is called genome-informed or personalized medicine. Personalized medicine is a new approach to medical treatment that uses a person's family history, medical history, and genes to manage their health.