It took 150 years to progress from Mendel's experiments with peas to the complete sequencing of the human genome. Host Bill Nye explores why certain traits are passed through families and species. He discusses the process by which scientists came to understand that inherited information is passed according to rules. Featuring discoveries related to DNA and its breakthrough as the chemical basis of genetic information, as well as a set of instructions for making the essential proteins of life. Nye also explains that RNA is the messenger that carries the instructions from living cells to enable protein production. Nye visits FBI headquarters in Washington, D.C., where DNA becomes personal. The discovery that DNA sequences are unique to each individual ushered in the era of criminal forensics, playing an important role in courtrooms ever since.