The Subdivision of the Chromosomes and their Multiplication in Non-Dividing Tissues: Possible Interpretations in Terms of Gene Structure and Gene Action

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Abstract
Evidence is presented that polysomaty and polyteny characterize differentiated tissues of Rhoeo and barley roots. The concept that all cells of an organism have the same chromosome and gene content is shown to be both inadequate and misleading. Four other concepts of chromosome structure and behavior are also criticized. The chromatid is a single "gene-string" in transmission genetics but cytologically it is often multi-stranded. This and many genetic data indicate that the gene has a structure which is unitary at one "level" but multiple at others. The lamellar concept of protein structure when applied to the gene offers a means of harmonizing many diverse data. Together with the total data on polysomaty in plants, insects and mammals, it makes possible new working hypotheses on the nature of gene action in differentiation and development. Various tests are suggested.