Genetic memory vs natural selection
sonigo at cochin.inserm.fr
Sat Oct 9 11:11:44 EST 1999
Mike Clark <mrc7 at cam.ac.uk> a écrit dans le message :
ant091128b49Pk=+ at mrc7acorn1.path.cam.ac.uk...
> In article <199910082057.SM00496@[184.108.40.206]>, Jay and Nancy Mone
> <URL:mailto:jaymone at PAONLINE.COM> wrote:
> > Pierre,
> > In all of my years as a biology teacher, I have never heard of the term
> > genetic memory. What in the world is it? As long as we are on the
> > subject, exactly what is a non-valid evolutionary history??
> > From a purely evolutionary standpoint, genetic adaptation is a shprt
> > phenomenon. Genetic variability can not anticipate future selective
> > pressures. Rather, natural selection for any phenotype provides
> > advantages to the cell or organism only in the present environment. If
> > that environment changes, any particular pre-existing adaptation may or
> > may not remain advantageous.
> > Jay Mone'
> This is an interesting question with regard to the immune response. There
> is no doubt that there are certain pathogens, infectious agents and other
> antigens which we are almost certain to meet in our lifetimes. As such it
> may be advantageous to inherit receptors specific for these types of
> antigen if we are able. In that way we are pre-prepared for the almost
> inevitable encounter. There are other antigens of a less predictable
> and for these an adaptive immune response which uses generation of
> diversity at the somatic cell level is advantageous. Many species use both
> strategies ie a balance between a large number of inherited receptors
> each with predefined ligands and an adaptive immune reponse involving
> T-cells, B-cells and immunoglobulin.
> I am also supportive of the idea that there is a degree of overlap between
> the inherited receptors of the innate immune response and rearranging
> receptors of the adaptive immune response. By this I mean that some of the
> V-region elements of the adaptive immune response already have a
> preselected affinity for some antigens such that an immune reponse can be
> generated very quickly by B-cells or T-cells with a high clonal frequency.
> Examples of this I would cite are the anti-blood group antibodies.
> Virtually everyone makes antibodies specific for the blood group alleles (
> mainly carbohydrate epitopes) that they don't inherit. These antibodies
> all encoded by common germline genes within the population which do not
> require extra somatic mutation to enhance their affinity for the sugar
> The inheritance of the receptor genes could be argued to be the genetic
> memory of the species.
> Mike Clark, <URL:http://www.path.cam.ac.uk/~mrc7/>
> o/ \\ // || ,_ o M.R. Clark, PhD. Division of Immunology
> <\__,\\ // __o || / /\, Cambridge University, Dept. Pathology
> "> || _`\<,_ // \\ \> | Tennis Court Rd., Cambridge CB2 1QP
> ` || (_)/ (_) // \\ \_ Tel.+44 1223 333705 Fax.+44 1223
Your hypothesis requires that individuals with high affinity antibodies to
blood group molecules had a selective advantage. Some antibodies protect
against the rhesus incompatibility problem during pregnacy. Is it what you
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