DNA, or deoxyribonucleic acid, is a molecule that encodes genetic information for the development and functioning of living organisms.
DNA is composed of chains of subunits that are called nucleotides (also called “bases”). There are four nucleotides: adenine (A), cytosine (C), thymine (T) and guanine (G). The specific order of these nucleotides in a DNA molecule is the DNA sequence and encodes the genetic information, much how the specific order of letters in a word conveys information to readers.
Inside your cells, two strands of DNA twist into a double helix shape. The nucleotides are paired in a very specific manner: an “A” nucleotide on one strand always pairs with a “T” on the other strand, and a “C” nucleotide on one strand always pairs with a “G” on the other strand. These A/T and G/C combinations are called base pairs. Almost every cell in the human body contains an identical copy of approximately 3 billion base pairs arranged into specific DNA sequences.