DNA (deoxyribonucleic acid)
The chemical "blueprint" for life. Genes are made of DNA and gene mutations can cause diseases.
DNA is a long chain of building-blocks (called nucleotide bases) that carries the genetic instructions (genes) for making living organisms. Each DNA building-block can be thought of as a "letter." When there's a gene mutation (or "spelling mistake" for even one letter), it can potentially create a non-functioning protein that causes disease. Each gene makes a messenger called RNA, which then is the template for making proteins, the actual work-horses of the cell. DNA is found in the nucleus of a cell where it is packaged into highly specific, long chains called chromosomes (there are 23 chromosome pairs in humans).