The human genom - how is it distributed?

David Konerding dek at socrates.ucsf.edu
Mon Mar 31 18:20:24 EST 1997


In article <3340124E.7DFC at unity.ncsu.edu>, Susan Hogarth wrote:
>William Tivol wrote:
>> 
>> Robert Lachmann (rolach at zedat.fu-berlin.de) wrote:
>> : I am having an arguement with a friend of mine about how the human genes
>> : are distributed on the DNA.That is, whether the human genes are
>> : distributed on both DNA strands or just on one.
>> 

Genes are distributed on both strands.  A segment of DNA could be as such:

5' >>>>>>>>>>>>>>>>>>>>>>::::::::::::::::::::::::::::::::: 3'
3' ::::::::::::::::::::::::::::::<<<<<<<<<<<<<<<<<<<<<<<<< 5'

Where : represents non-coding DNA and > and , represent coding DNA.

As you may see, both strands contain coding DNA (genes).  The direction
of coding depends on the strand- all genes on the top strand will code
genes in one direction (left to right in this case) and genes in the
bottom strand will code in the opposite direction.

The E.Coli genome contains examples such as:

::::::::::>>>>>>>>>>>>>>>>>>>:::::::::::::::::::::
::::::::::::::::::::<<<<<<<<<<<<<:::::::::::::::::

where two genes occupy the same DNA but opposite strands and run
in opposite directions.  I've always been amazed at this sort of coding
because it implies a certain co-evolution of the genes.   For example,
since there are really only three start codons and three stop codons,
there are only certain mutations which could occur in the amino acid
coded for by the reverse complement of the start codon of a gene.

-- 
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Email: dek at cgl.ucsf.edu    David Konerding     WWW: http://picasso.ucsf.edu/~dek
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