A Re-Examination of Rahn's Data on the Number of Genes in Bacteria

A CCORDING to current cytogenetic theory, each chromosome in every I cell of a living organism comprises a number of genes. Inter alia, these genes have the following properties:(a) They are the carriers and transmitters of hereditary characters; (b) They control the specific enzymatic activity of the cell; (c) They play an important part in the initiation of cell division. This paper is concerned only with the third of these properties, and with the light it can throw on the numbers of genes in a cell. The natural process of cell division must be preceded by duplication of the constituent chromosomes, which in turn requires the duplication of every gene and is the culmination of an elaborate synthetic process. Luria (1950) has pointed out that 'There is something peculiar to homologous replication that sets it aside from other types of synthetic reactions. The replication of specific biological units must involve the building of complex specific molecules or molecular aggregates, the only permissible limitation to identity of model and replica being the production of mutated structures the production, that is, of modified elements replicated in the modified form'. Claude (1949) has emphasized the difficulties in this 'template theory, elaborated to account for the supposedly unique process of gene reproduction', which 'assumes that the gene or the chromosome serves as a mold for the systematic apposition of a new substance'. He goes on to state that 'in the light of biochemical processes already known, it is conceivable that the duplication of essential and characteristic cell substances is the end