D. L. Nanney,
Biology Department, University of Michigan, Ann Arbor, MI USA
Conclusion:
This discussion is based on the idea of two types of cellular regulatory systems, both capable of maintaining persistent cellular characteristics but achieving homeostasis by different means. The current concept of a primary genetic material (DNA), replicating by a template mechanism, is opposed to a homeostatic system operating by, perhaps, self-regulating metabolic patterns. 11 The details of operation in neither type of system can be precisely determined at the present time, and any attempt to discriminate between them may be premature. Certainly, an operational distinction at the present time encounters great difficulties. Nevertheless, a recognition of the existence of the two types of systems, and even the difficulties in distinguishing between them, may be useful in avoiding confusion in discussing cytoplasmic inheritance, developmental alterations, inheritance of acquired characters, mutation, and genetic recombination.
References:
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and
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1. Brink RA, "Paramutation and Chromosome Organization", Quart. Rev. Biol. vol. 35, pp. 120-137 (1960).
2. "Gene De-Repression", New Eng. J. Med. vol. 288, pp. 1224-1229 (June 7, 1973).
3. "Activation of DNA Transcription within Repressed Chromatin", 14th John Innes Symposium, 2001.