Gene

From EvoWiki

Contents 1 Introduction 2 Definitions of gene 2.1 The "Muton" 2.2 The "Recon" 2.3 The "Cistron" 2.4 The "Optimon" or "Selecton" 3 References & Further reading 3.1 External Links 4 To do list 5 See also

Introduction

A gene is roughly defined as a "unit of heredity". The exact definition of the word varies slightly, but all definitions refer to a section of a chromosome. Before, the discovery of DNA the word simply meant an arbitrary unit of heredity: any section of a chromosome. Since the discovery of DNA and development of modern genetics, and the knowledge of processes such as mutation, crossing over and transcription have meant that a number of different definitions of gene have arisen. Benzer (1957), Dawkins (1978 & 1982) and Mayr (Dawkins 1982) have coined a number of new terms to avoid confusion.

Definitions of gene

The "Muton"

This is the minimum unit of DNA that is subject to mutational change.

The "Recon"

This is the minimum unit of DNA that is subject to recombination. This in turn is determined by the number of generations over which the recombination can act. In a single generation a single recon may be very long, but over many generations the length of DNA affected (directly) by recombination will be small.

The "Cistron"

A cistron is a length of DNA that is transcribed into a single length of messenger RNA, and from there into a single polypeptide (protein) chain.

The "Optimon" or "Selecton"

The optimon is defined by Dawkins as the unit of natural selection: that is, the "purpose" of adaptations is the survival of the optimon. Dawkins (1976 & 1982) argues that the optimon is a unit of DNA that survives recombination for enough generations to be selected for together, and not an individual organism or group.

References & Further reading

1. Benzer, S (1957). The elementary units of heredity, in The Chemical Basis of Heredity (eds W.D. McElroy & B. Glass), pp. 70-93. Baltimore, John Hopkins Press. Cited in Dawkins 1982.
2. Dawkins, R (1976). The Selfish Gene. Oxford University Press.
3. Dawkins, R (1978). What is the optimon? University of Washington, Seattle, Jessie & John Danz Lecture. Unpublished, cited in Dawkins 1982.
4. Dawkins, R (1982). The Extended Phenotype, Chapters 5 & 6. Oxford University Press.

External Links

• Wikipedia: Gene

To do list

• Gene expression - transcription & translation
• Gene regulation - transcription factors, regulatory elements etc

See also

• Genetics
• Gene expression
• Genotype

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