 Philosophers responded to these genetic discoveries in different ways—by proposing multiple gene concepts, or by trying to unify the disparate phenomena under a single gene concept. Lenny Moss’s distinction between Gene-P and Gene-D is a classic example of the multiple gene concepts approach (Moss 2002). Gene-P embraced an instrumental preformationism; it was defined by its relationship to a phenotype. In contrast, Gene-D referred to a developmental resource; it was defined by its molecular sequence. An example will help to distinguish the two: When one talked about “the gene for cystic fibrosis”, the Gene-P concept was being utilized; the concept referred to the ability to track the transmission of this gene from generation to generation as an instrumental predictor of cystic fibrosis, without being contingent on knowing the causal pathway between the particular sequence of DNA and the ultimate phenotypic disease. The Gene-D concept, in contrast, referred instead to just one developmental resource (i.e., the molecular sequence) involved in the complex development of the disease, which interacted with a host of other such resources (proteins, RNA, a variety of enzymes, etc.) (entry:  gene).  (For other examples of multiple gene concepts, see Fox Keller 2002; Baetu 2011; Griffiths and Stotz 2013).