What Is DNA?
DNA is a polymer (or chain) of individual monomers (or units) called nucleotides. Each nucleotide contains a "base" that identifies it; there are four bases: cytosine (abbreviated C), adenine (A), thymine (T), and guanine (G). Multiple nucleotides (millions, even) can be strung together into chains, and two chains cling together with hydrogen bonds to form a double helix. This double helix constitutes a molecule of DNA:
Thus, your DNA is responsible for making you (although the exact influence of genes versus environment in your development and behavior is a topic of hot debate).
Changes in DNA also affect people directly. Mistakes, or mutations, from radiation, errors in copying, and other sources can cause developmental disorders, like Down Syndrome, and cancer. Much research is trying to prevent and fix detrimental mistakes. Most importantly of all, mutations in DNA underlie the process of evolution by natural selection, but that's another story for another day!
And that, my friends, is DNA in a bathroom break.