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Is there a relation between gene-size and gene function ?

James McInerney james.o.mcinerney at may.ie
Mon Oct 20 15:14:05 EST 2003

On 20/10/2003 07:55 AM, "BioLogics" <I_am_somebody at hotmail.com> wrote:

> Hi,
> I was working on a related datafile when a thought hit me; should i
> expect that genes exhibiting similar functions across species also have
> the same gene-size?
> Pubmed searches did not answer my Q. Some insightful comments are welcome.

I'm afraid the story is more complicated.

Whilst we might expect that many homologous/orthologous proteins would have
similar sizes, particularly if they perform the same functions in different
species (as seems to be the import of your question), it is not _necessary_
for them to be the same or even similar sizes.

Proteins in the pufferfish, for instance are much shorter than their human

Proteins might catalyse the same reaction and not even be related to each
other - we see this in Fatty Acid biosynthesis in Mycobacterium
tuberculosis.  There is a protein catalysing a particular part of the
pathway and it is not homologous to the protein that carries out the same
reaction in other bacteria.

In fact for the fatty acid biosynthesis pathway in tuberculosis, there are 7
proteins responsible, in humans there is one multifunctional protein.

So, while there may be correlations, and in some cases, very good
correlations, particularly between closely-related species, it is not a good
rule that they would be of similar size.


Dr. James O. McInerney,
Bioinformatics Laboratory,
Department of Biology, National University of Ireland,
Maynooth, Co. Kildare, Ireland.
P: +353 1 708 3860
F: +353 1 708 3845
E: james.o.mcinerney at may.ie
Take a look at our website --- http://bioinf.may.ie/


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