Table 1. Abridged list of different propositions for a definition of the gene in the current era given by different authors.

Essential Content or Character of the Proposition	Classification	Author(s)
These three first operational definitions give criteria, formal, experimental and computational, for identifying genes in the DNA sequences of genomes, annotation of genomes, and for specifying the function of genes	Operational	Snyder and Gerstein (2003)
	Operational	Pesole (2008)
	Operational	Stadler et al. (2009)
In these three following definitions, classified as molecular, the structural and the functional gene are conceptually distinguished and separated	Molecular	Scherrer and Jost (2007)
	Molecular	Keller and Harel (2007)
	Molecular	Burian (2004)
In this definition two gene concepts, “gene-P (preformationist)” and “gene-D (developmental)”, are distinguished	Complex	Moss (2003)
This definition presents three different concepts of the gene: instrumental, nominal and postgenomic	Complex	Griffiths and Stotz (2006)
This definition aims at to define the gene on the basis of its products and separates it from DNA	A new kind of redefinition	Waters (1994)