Mammalian Exon Size: Upper Limit

Keith Robison robison1 at
Wed Jun 10 11:12:08 EST 1992

khofmann at writes:


>Looking at the current query for the biggest internal exon, another question
>comes to my mind:

>What is the size of the smallest introns found in higher eukaryotes?
>I would imagine that, considering current knowledge of the splicing
>process, there should be a definitive lower limit for intron lengths.

A _very cursory_ check of the plant division of GenBank finds a
15 bp intron in the major latex protein gene from poppy(PAPMLG X54306).  
I don't know whether to believe this.  A number of introns in plants
appear to be in the 40's.

>or, more generalized, where do those kind people who answer those questions
>get their figures from? Is there any kind of computer program available,
>scanning the databases and giving information of the type mentioned above?

I am using a local copy of GenBank 71 and some custom software designed
for extracting reading frames from multi-exon genes in GenBank*, plus
some UNIX manipulations.  It worked well for the original "biggest exon"
query, and not so well for this one.

>I remember several examples of 'what is the biggest....' questions on the
>net over the past few years. Perhaps someone should publish a Guiness-File of
>molecular biology, holding entries like: the biggest or smallest intron or
>exons ever, the biggest/smallest genomes, or, as already asked in the past,
>the biggest insert ever cloned into pUC. :-)

Sounds interesting!

>        Kay

Keith Robison
Harvard University
Program in Biochemistry, Molecular, Cellular, and Developmental Biology

robison at 

* -- software available upon request.  Users must be willing to put
     up with a high level of idiosyncrasity and a moderate level
     of user hostility :-)

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