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Trinucleotide repeats

Shane McKee shane at reservoir.win-uk.net
Wed Dec 14 08:17:27 EST 1994

Hi there!

I was wondering if anyone is aware of any published material on the
role of trinucleotide repeats in the production of genetic
variation, both within and between species. Variable Number Tandem
Repeats (VNTRs) are regions of DNA which contain the same short
sequence repeated many times, and can thus be described as (seq)n
, where seq is a sequence of bases, eg CAG, ATGT, etc. These VNTRs
of which trinucleotide repeats are a subset, often vary between
individuals in the number of repeat units they contain, and can
thus be used as informative polymorphisms for gene linkage

        In recent years, trinucleotide repeats have been linked to
several inherited diseases, such as myotonic dystrophy,
Huntington's disease and Fragile X syndrome. It seems that
individuals affected by these diseases possess many more repeat
units at the relevant locus than unaffected individuals, and the
more repeats they have, the more severe the disease tends to be.

        In most textbook discussions of gene mutation ( forgive me
for not keeping up with the literature ), attention seems to be
focused on point mutations affecting the amino acid sequence of
a protein, and thus its function. While undoubtedly important, it
seems inadequate to explain some of the finely balanced properties
of gene expression. VNTRs may be able to play a role in gene
expression by being placed between a gene's promoter and the start
of the exon, or between exons themselves, and the sheer physical
DNA distance which must be transcribed may influence the success
of the whole operation, and hence the expression of the protein.
This could be potentially a very important mechanism for
introducing genetic variation upon which evolution may act.

        Anyway, any thoughts on the matter?

Shane McKee [Shane at reservoir.win-uk.net]
           " Art becomes Science when you start trying
             to figure out what the hell you're doing. "
                NB: IMHO, MHO = *M*HO.

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