absence of introns in vertebrates

Rcjohnsen rcjohnsen at aol.com
Mon Mar 6 03:04:40 EST 2000


<< Subject: Re: absence of introns in vertebrates
From: Mike Syvanen syvanen at ucdavis.edu 
Date: Tue, Feb 29, 2000 11:05 PM
Message-id: <89hjbd$319$1 at mercury.hgmp.mrc.ac.uk>



Rcjohnsen wrote:

> << Subject: absence of introns in vertebrates
> From: Alain Bernot bernot at genoscope.cns.fr
> Date: Mon, Feb 14, 2000 5:16 PM
> Message-id: <889d96$92r$1 at mercury.hgmp.mrc.ac.uk>
>
> Hi
>
> I am looking for exemples of genes whose introns/exons organization is known
> in several species (in vertebrates), for which in one species the gene
doesn't
> contain any intron but is functionally transcribed.
>
> thanks in advance >>
> You might try searching for pseudogenes where it is thought that RNA was
> reverse transcribed back to DNA and inserted.  There are a number known but I
> don't know if any are functional.

If it is functional, it is not a pseudogene.  But I know what you mean.
Look up chicken calmodulin, that might be a candidate.
 >>
Sorry on my missuse of the word pseudogene.  I found one in a plant(below) and
I think there's one or more in mammals.

http://arabidopsis.org/madison97/at97abs/imar_12-12.html

THE catalase genes of Arabidopsis and other angiosperms: a mechanism for the
evolution of a multi-gene family.
Julia Frugoli (1), Mark McPeek (1), Terry Thomas (2), C. Robertson McClung (1)
(1) Biology Department, Dartmouth College, Hanover, NH 03755, USA; (2) Biology
Department, Texas A&M University, College Station, TX 77843, USA [presenter's
e-mail: jfrugoli at bio.tamu.edu]
We describe a phylogenetic analysis of 34 plant catalase genes, including three
from Arabidopsis thaliana. One Arabidopsis catalase gene, CAT1, lies less than
500 base pairs from the polyadenylation site of another family member, CAT3.
Both genes are transcribed in the same direction. Although our analysis
suggests that the ancestral plant catalase sequence includes multiple introns,
the CAT1 sequence lacks introns. In addition, CAT1 contains a polyA stretch in
the 3' untranslated region, suggesting that it may have arisen by reverse
transcription of an ancestral CAT1 mRNA. However, CAT1 is expressed as an mRNA
that is apparently translated to yield a full-length and functional catalase
subunit, and CAT1 mRNA accumulation is organ-specific and light-responsive,
suggesting that CAT1 is not a pseudogene. We suggest the following sequence of
events in the evolution of the Arabidopsis catalase gene family. An initial
duplication of an ancestral, intron containing catalase gene yielded CAT3 and
CAT1. A second duplication event involving CAT1 generated the unlinked gene,
CAT2. After this second duplication event, a reverse-transcribed intronless
CAT1 cDNA replaced its genomic copy by homologous recombination. Patterns of
intron loss in a cereal catalase lineage of the gene tree support the proposed
mechanism, which may represent a common mechanism of intron loss in the
evolution of plant gene families. Supported by grants from the USDA (CRM), and
the NSF (CRM, JAF).

also try
http://www3.ncbi.nlm.nih.gov/htbin-post/Omim/getmim?search=intronless+not+
pseudogene

There should be 10-12 listed there

---







More information about the Mol-evol mailing list