To understand epigenetics, we first need to know some basic genetics.
Genes are made of deoxyribonucleic acid (DNA)*. DNA consists of long strings of four component molecules*, called bases*: A, C, G and T. The order, or sequence, of these bases along the string serves as our genetic code.
Two long strings of DNA coil around each other to form the famous double helix structure. The bases on one strand form connections with the bases on the other strand; these connected pairs are the “rungs” in the twisted ladder-like structure of the helix. A always connects to T, and C always connects to G.
Connections between matching, or “complementary”, bases on opposite strands of DNA - A-T and C-G - hold the structure of the double helix together.