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Manoj Joshi, Social Zerology, Physics (atmmmj@vax.oxford.ac.uk) wrote: : can anyone xplain to me what a gene is? See Portin, 1993, "The Concept of the Gene: Short History and Present Status", Quarterly Review of Biology 68(2): 173 - 223 The author argues that the concept of the gene has gone through three periods, which he calls classical, neoclassical and modern. The classical view is the gene is an indivisible unit of genetic transmission. The neo-classical view is that the gene (sometimes called a cistron) was responsible for producing a single mRNA and hence a single protein. The modern view, in the author's mind, incorporates split genes, alternate splicing, over- lapping and nested genes as well as edited genes. I've only skimmed the article (but let me add my highly biased and tendentious opinions anyway8-) but I think the author is confusing what a gene is with the form a gene takes. I subscribe to a view that would be closest to the classical view -- a gene is a heritable unit capable of being passed on intact for numer- ous generations. The form that most genes take is a string of nucleotides that code for a single protein. But, other elements can be stably inherited and (IMHO) can be viewed as genes. For an example, I would give cytoplasmic elements such as _Wolbachia_ bacteria, which is a cytoplasmically transmitted parasite that alters sex-ratios in many insects. (It boosts the percentage of females produced because it is not passed on through males). The molecular biologists definition of a gene as a nucleotide sequence is (IMHO) far too restrictive. Chris Colby email: colby@biology.edu

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