  A different image emerges from viewing genetics as an investigative science involving an interplay of methodological and explanatory reasoning (Waters 2004a). This image is not of a two-tiered science, one (classical genetics) aimed at investigating and explaining transmission phenomena and another (molecular genetics) aimed at investigating and explaining developmental phenomena. Instead, there is one science that retains much of the investigative and explanatory reasoning of classical genetics by re-conceptualizing its theoretical basis in molecular terms and by retooling its basic investigative approach by integrating methodologies of classical genetics with physically-based methods of biochemistry and new methods based on recombinant DNA and RNA interference technologies.