Different positions of i

arlin at ac.dal.ca arlin at ac.dal.ca
Tue Feb 28 15:24:08 EST 1995

In article <3iho7r$q8d at nuscc.nus.sg>, medp3019 at leonis.nus.sg (Ng Hian Cheong) writes:

> Dear colleague,
>   Is it possible for descendents of the same ancestral gene to 
> have different numbers and postions of their introns in different
> species of organisms ?
>  I have cloned a gene (from a protozoa) which is 
> homologous to all members of a particular family of 
> protein kinase. Most members of this family documented in databases are 
> from plants. These genes displayed 10 introns where genomic sequences are 
> available and the positions of their introns are conserved.
>   Assuming my gene originated from the same ancestral gene as those with 
> 10 introns, what is the explaination for the observed differences?

This shouldn't be cause for worry.  It is very common to find  intron
positions that are not conserved between distantly related genes. 
For another recent report of the pattern you have observed, see

Dietmaier and Fabry, 1994. Analysis of introns in genes encoding small G
proteins.  Curr. Genet. 26: 497-505.

The authors find more than 60 different intron positions in their examination
of this gene family.  Most of the observed intron positions exhibit a 
restricted phylogenetic distribution, leading the authors to conlude that
"the present data are more consistent with the hypoethesis that most, if
not all, of the introns now existing in SGP [small G protein] genes are
the result of independent insertion events that occurred at various
stages of eukaryotic evolution" (p. 504).


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