VARIATION IN DNA CONTENT AMONGST DIFFERENT SPECIES

Keith Robison robison1 at husc10.harvard.edu
Sat Jan 29 12:24:32 EST 1994


garfinkl at iitmax.iit.edu (Mark D. Garfinkel) writes:

>afc at gnv.ifas.ufl.edu (Andrew Cockburn) writes:

>>It is correct that most genomic DNA in higher eucaryotes is noncoding.
>>However, the argument that most of this is repetitive is blatantly
>>homocentric.
>        *Also, let's remember that a significant portion of human
>repetitive DNA, namely the Alu repeats, code for the 7SL RNA that is a
>component of signal recognition particle. Not all "complex" repetitive
>DNA is retrotransposon or other selfish DNA, or "mysterious" in some way.

Alu repeats evolved from the 7SL RNA gene, but don't believe Alu's
actually produce functional 7SL RNAs.  

>...

>>What I would like to see is an explanation of how a small genome
>>can evolve from a large genome full of repeats.  I believe that this

Readers of this thread should note the recent paper from 
Sydney Brenner's group on the fugu (pufferfish) genome --
less than 1/2 a gigabase and apparently relatively free of
repetitive sequences.  The paper was in Nature in November
(366:265 + a News&Views I think).  Brenner thinks that fugu
represents an unexpanded, ancestral genome type but it's not
obvious that it is not a reduced genome which ejected the 'junk'.

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

krobison at nucleus.harvard.edu 







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