Intron loss?

Martin Kennedy mkennedy at
Fri Nov 12 00:08:28 EST 1993

In article <56808 at>, rounsley at (S. Rounsley) writes:
>............. Now if we
> find a gene that is missing one of these introns, it would seem
> to me that this indicates a loss of an intron, rather than a
> gain of the intron by all the other members of this family.  Are there
> any good examples of this in related gene families, and if so, what
> is the consensus of the mechanism by which this could happen?
> Could the introns precisely excise , as with transposable
> elements?  What about possible mechanisms involving integrations
> of spliced RNA molecules into the genome..
 	Steve Rounsley


Many pseudogenes appear to be derived from the insertion of cDNA copies of
transcripts into the genome.  It is not uncommon for gene families to include
several members which are intron-less pseudogenes, often with point mutations
etc that mean they cannot be translated into a functional protein.  I'm no
expert on this, but I know that there are at least two pseudogenes for human
DHFR, I've heard that there are many actin pseudogenes in the genome, and I'm
sure there is an enormous literature on pseudogenes in other gene families. 
Don't forget that there are endogenous mammalian (including human) reverse
transcriptases, so there is a good mechanism, and several examples of,
integration  of cDNA copies of transcripts into the genome.

A look in my files turned up some relevant (and mostly dated) references:

Nature 301, p471
Nature 326, p501
Science 254, 1808

Hope this is useful,


NNNN   NN  Martin A Kennedy (E-mail = mkennedy at  ZZZZZZZ  
NN NN  NN       Cytogenetic and Molecular Oncology Unit          ZZZ
NN  NN NN           Christchurch School of Medicine            ZZZ
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