Those of you who do not know who Bill Nye the Science Guy! is will especially enjoy this video. In this streaming episode, Bill Nye the Science Guy explores the science behind genes (part 2). Basically, you can thank your parents for all those nice pairs of genes. Chromosomes are made up of sequences of genes, which are themselves made up of strands of DNA. The mutations in DNA during replication cause resulting changes within genes, which is the basis of evolution. The third and last part appears tomorrow morning. [6:17].