  This article begins by providing a quick review of the basic theory associated with molecular genetics. Since this theory incorporates ideas from the Morgan school of classical genetics, it is useful to sketch its development from Morgan's genetics. After reviewing the basic theory, I examine four questions driving philosophical investigations of molecular genetics. The first question asks whether classical genetics has been or will be reduced to molecular genetics. The second question concerns the gene concept and whether it has outlived its usefulness. The third question regards the tenability of the fundamental theory. The fourth question, which hasn't yet attracted much philosophical attention, asks why so much biological research is centered on genes and DNA. 