This paper investigates what molecular biology has done for our understanding of the gene. I base a new account of the gene concept of classical genetics on the classical dogma that gene differences cause phenotypic differences. Although contemporary biologists often think of genes in terms of this concept, molecular biology provides a second way to understand genes. I clarify this second way by articulating a molecular gene concept. This concept unifies our understanding of the molecular basis of a wide variety (...) of phenomena, including the phenomena that classical genetics explains in terms of gene differences causing phenotypic differences. (shrink)

In a reply to Marga Vicedo the philosophical inconsistency of Morgan is emphasized. It is argued that even if a strict classification of scientists according to their philosophical position is not possible, their science may still be influenced by their philosophical ideas. Finally it is suggested that philosophical ideas influence science less by a direct effect on the scientists than indirectly through science policy and administration.

The classical view of the gene prevailing during the 1910s and 1930s comprehended the gene as the indivisible unit of genetic transmission, genetic recombination, gene mutation and gene function. The discovery of intragenic recombination in the early 1940s led to the neoclassical concept of the gene, which prevailed until the 1970s. In this view the gene or cistron, as it was now called, was divided into its constituent parts, the mutons and recons, materially identified as nucleotides. Each cistron was believed (...) to be responsible for the synthesis of one single mRNA and concurrently for one single polypeptide. The discoveries of DNA technology, beginning in the early 1970s, have led to the second revolution in the concept of the gene in which none of the classical or neoclassical criteria for the definition of the gene hold strictly true. These are the discoveries concerning gene repetition and overlapping, movable genes, complex promoters, multiple polyadenylation sites, polyprotein genes, editing of the primary transcript, pseudogenes and gene nesting. Thus, despite the fact that our comprehension of the structure and organization of the genetic material has greatly increased, we are left with a rather , open and general concept of the gene. This article discusses past and present contemplations of genes, genomes, genotypes and phenotypes as well as the most recent advances of the study of the organization of genomes. (shrink)

Definitions of the term gene typically superimpose molecular genetics onto Mendelism. What emerges are persistent attempts to regard the gene as a unit of structure and/or function, language that creates multiple meanings for the term and fails to acknowledge the diversity of gene architecture. I argue that coherence at the molecular level requires abandonment of the classical unit concept and recognition that a gene is constructed from an assemblage of domains. Hence, a domain set (1) conforms more closely to empirical (...) evidence for genetic organization of DNA regions capable of transcription and (2) has ontological properties lacking in the traditional unit definition. (shrink)

Genetics was established on a strict particulate conception of heredity. Genetic linkage, the deviation from independent segregation of Mendelian factors, was conceived as a function of the material allocation of the factors to the chromosomes, rather than to the multiple effects (pleiotropy) of discrete factors. Although linkage maps were abstractions they provided strong support for the chromosomal theory of inheritance. Direct Cytogenetic evidence was scarce until X-ray induced major chromosomal rearrangements allowed direct correlation of genetic and cytological rearrangements. Only with (...) the discovery of the polytenic giant chromosomes in Drosophila larvae in the 1930s were the virtual maps backed up by physical maps of the genetic loci. Genetic linkage became a pivotal experimental tool for the examination of the integration of genetic functions in development and in evolution. Genetic mapping has remained a hallmark of genetic analysis. The location of genes in DNA is a modern extension of the notion of genetic linkage. (shrink)