Single nucleotide polymorphisms (SNPs) are the most common types of genetic variation among people.
Deoxyribonucleic acid (DNA) is the chemical compound that contains the instructions needed to develop and direct the activities of nearly all living organisms. DNA molecules are made of two twisting, paired strands, often referred to as a double helix.
The three billion letters of the human genome are written using the four-letter alphabet of DNA. The DNA is divided among 23 pairs of chromosomes that are found in each of the trillions of cells in our bodies.
DNA basics: What it is, what it does, and where it's found