Pilgrim Trust Lecture - The gene

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Abstract
A review, with 148 references. The exact duplication of mutants from pure lines is explained by the self-multiplying pattern or gene. That genetic material in chromosomes is nucleoprotein is confirmed by the analogous finding in viruses. Mutations in Drosophila are particulate at the level of the single gene with probability of less than one per million of a given gene mutating in a given cell cycle. Most mutations are deleterious, are localized at the ultramicroscopic level, and may be due to thermal agitation, since a rise of 10[degree] C causes a several-fold rise in gene-mutation frequency. Mutation is greatly increased by ionizing radiation (X- or y-), but the sparse radiation in nature accounts for few mutations. The internal structure of the gene is non-repetitive since mutants do not dissociate into a mixture of all-mutant and all-original. A maximum diam. of 0.05 u per gene is based on some dozen breaks in the chromosome under the influence of X-rays falling into just 4 definite positions. Relation of the gene-number, estimated from crossing-over frequencies or mutation frequencies, to the volume of the chromosome indicates the same gene size. Mutations occur more frequently in young than in old individuals. Mustard gas increases the frequency of spontaneous mutation. Cytoplasmic genes, lacking fixed arrangement, lack potentialities for persistence and evolution. Chromosomal genes are increased by the insertion of a small piece of chromosome in a chromosome line and its later mutation. Gene duplication is considered analogous to chromosomal synapsis, based on a vibrational or ionic atmosphere attraction, possibly involving the natural polymerized nucleic acid as a patterning complementary matrix. There is insufficient evidence to support either the enzymic or antigenic theory of primary gene products. Genes may undergo changes in their effects by shifting their position in the chromosome without mutation, restoration of normal position reestablishing the normal effect, so that gene specificity may be related to the particular folding pattern of the relatively simple nucleoprotein. Crossing-over is the key to evolution and distribution of mutations in sexual forms. The evolution and even the maintenance of a species requires a dynamic equilibrium between mutation and selection.

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