Sets of genes encode cellular programs, also called cellular activities. Genes are made of DNA. DNA is the abbreviation for the chemical deoxyribonucleic acid. DNA is a very long molecule. It looks like two strands wrapped around each other, resembling a twisted ladder or double helix. DNA is coiled into chromosomes, found in the nucleus of every cell. There is also a little bit of DNA in another part of cells, organelles called mitochondria.