Andrew J. Roger aroger at ac.dal.ca
Fri Sep 8 14:32:26 EST 1995

tz68 at aol.com (TZ68) wrote:
>Do pseudogenes arise from recent or ancient events?  Does one arise from a
>functional gene and can a functional gene arise from a pseudogene?  What
>value are pseudogenes?
>Just Curious

It is my understand that pseudogenes are the result of processed
(usually) mRNA being reverse transcribed (spuriously) and the
resulting DNA version being reintroduced into the genome by
illegitimate recombination.  Since many pseudogenes are truncated
versions of the original gene and may not insert into a transcribed
region of the genome, they may not ever get a chance to be
"functional" in the sense of expression and translation of
a protein product which has some activity.  On the other hand
given the right conditions, there is no reason why they couldn't
give rise to a functional gene.  As for their age, it really
depends on what pseudogene you are looking at. It is likely that
"functionless" pseudogenes will become unrecognizable (due to
nucleotide substitution) after about 100 million years.  You
might consider this ancient if you worked on the evolution of
Homo sapiens and thought 1 million years was a long time.
On the other hand, if you worked on the primary radiation
of animal phyla- then most pseudogenes are pretty recent
by these standards!

Andrew J. Roger

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