about introns

alvaro mailhos alvaro at genetica.edu.uy
Mon May 11 14:00:19 EST 1998

>I cannot quote chapter and verse but here are a couple of generalisation
>that I think may answer your question.
>1) The start codon of a gene need not be in the first exon. ence, the 5'
>UTR need not be encoded in a single exon. The example that comes to mind is
>the per gene in Drosophila.
>2) The stop codon is almost always in the last exon of the gene and so it
>is very rare for an intron to be present in the 3' UTR. I know that there
>is at least one exception to this but cannot remember an example. Can
>anybody else help?
>Raymond Dalgleish
>Department of Genetics
>University of Leicester
Thanks for your answer! I actually found a couple of cases where the
initial Met is not in the first exon (and here a semantics question: a
collegue of mine insists that if does not correspond to a coding sequence
you cannot call it an exon. Is this right?). The question actually is does
anyone know of a case where the first menthionine is encoded in exon 3 or

And another question, any of you know a good review of the consensus
regulatory sequences in the 5' and 3' UTRs? From what I have read these
regions would be critical for the modulation of the translation of the
mRNA, are there any factors binding to regulatory sequences in these=

Thanks again (specially to Raymond D.!!!),

Alvaro Mailhos
Laboratorio de Evoluci=F3n
Facultad de Ciencias
Igu=E1 c/ Mataojo
11400 Montevideo, Uruguay

Phone: (+598 2) 525 86 18/ext. 143
E-mail: alvaro at genetica.edu.uy

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