Chromosome control sequences

Mazda Hewitt Mazda.Hewitt at bbsrc.ac.uk
Tue Dec 3 06:04:58 EST 1996


Hermund Årdalen wrote:
> 
> We have a few questions regarding the chromosome structure and how the
> cells access the proper genes:
> 
> Could any of you explain how the cells figure out where in the
> chromosome to find the genes that it shall use for its proteine
> synthesis?
> 

Hmm, It is not possible to aswer your question as cells do not need to
find genes that are used for protein synthesis.  The machenery that is
used for protein synthesis is floating freely in the cell (soluble
enzymes) and just happens to make contact with the genes it transcribes. 
The specific concentration of the machenery and the concentration of DNA
determined how likely for the machenery to make contact with the DNA.

At the begining of the gene there is what is called a promoter which
identfies this piece of DNA as a gene and starts the transcribing
machinery working.

> What is the deciding factor for which genes to be read in a cell?
>
The answer to this question is complecated, in short there is no single
deciding factor which determines which genes are read and which are
not.  
Promoters can be swiched on or off by the presence of other proteins,
DNA can be methylated wich reduces the amount of protein which is made
from the gene, Other factos such as the position of the gene in relation
to other genes amy also affect this, so the answer is not cut and dry.
 
> Are there special types of basepair sequences that act as start and stop signs for genes?
> 
yes.  For other things like this you can find the answer in a high
school text.

> If you don't know the answer, do you know where on the Internet we could
> find documentation on this?
> 
> --
> Hermund Aardalen <hermunda at ifi.uio.no> http://www.ifi.uio.no/~hermunda/
> WWW Snooker - http://www.ifi.uio.no/~hermunda/Snooker/



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