1. DNA (deoxyribonucleic acid) is a chemical found in the nuclei of living cells that controls cellular functions and determines traits by containing the genetic instructions for development. 2. DNA is a long chain molecule composed of nucleotides, each containing a sugar, phosphate group, and organic base. The bases bond with each other in specific pairs to form the signature double helix structure. 3. DNA replicates itself before cell division so that each new cell contains an identical copy of the original DNA sequence of genes and genetic instructions. This ensures traits are passed down from parents to offspring.