  Perhaps the reason gene skeptics overlooked the molecular gene concept is that they were searching for the wrong kind of concept. The concept is not a purely physicochemical concept, and it does not provide a single partition of DNA into separate genes.  Instead, it is a functional concept that provides a uniform way to think about genes that can be applied to pick out different DNA segments in different investigative or explanatory contexts. The basic molecular concept, according to this analysis, is the concept of a gene for a linear sequence in a product of DNA expression: