Why are there 23 pairs of chromosomes?

Graham Dellaire popa0206 at PO-Box.McGill.CA
Sat Jul 15 21:18:23 EST 1995


>  
>  On a related vein, has anyone read Gunter Blobel's gene gating hypothesis? It was published in 
1985
>  in PNAS (I can't remember the volume offhand..), and he proposes that the 3D structure of the 
genome 
>  changes throughout development and that this may have some effect on gene transcription. Could 
it be 
>  that this "junk DNA" is fundamentally important for the topological dynamism (assuming his 
hypothesis is
>  correct) of the genome of an organism during development (or disease, for that matter!!) ?
>  


Hello Nick,

I am a firm believer that all the so called "junk" in the genome has function... whether  it is in
maintaining regions of homology for "gene conversion and recombination" during chromosome
pairing in meiosis or perhaps more fundementally in control of  transcription and replication
of different regions of the genome...

some recent data has shown that this "junk" may be transcribed into RNA that is functional...

ex. XIST RNA which appears to be involved in X-chromosome inactivation

or Lin-4 which bind the 3' UTR of the RNA of another protein LIN-6 and prevents its
translation in C. elegans.

I think genes have been focused on for too long while the context of the gene has been
ignored... probably because alot of the pioneering work has been done bacteria and yeast 
who have a paucity of "junk" dna and are gene "rich" genomes.

Someone asked me once why I wasn't in Yeast or bacteria as I wanted to study recombination..?
I am in mammalian genetics and I reply only that someone has to do it! <grin>....  The system
is infinately more complicated and down right stubborn but it is after all a little closer to home.
But I am not dumping on Yeast or Bacterial genetics.... thank God for these organisms and the
body of research on them.... without it I wouldn't know where to start and articles in my field
would be far and few between.


Graham

>                                                                                                Nick.
>  
>  
>>>>



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