Different positions of i

Keith Robison robison at lipid.harvard.edu
Mon Feb 27 08:50:11 EST 1995

Ng Hian Cheong (medp3019 at leonis.nus.sg) wrote:
: 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?

While the precise analysis of the subject remains controversial, it
is well accepted that introns can be lost and gained from genes.
Intron gain probably results from the insertion of a transposon
and splicing around the transposon (I think this has been directly
demonstrated with a plant transposon).  Intron loss probably results
from reverse transcription of an mRNA followed by homologous recombination.

Keith Robison
Harvard University
Department of Cellular and Developmental Biology
Department of Genetics / HHMI

robison at mito.harvard.edu 

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