newbie question about DNA and cells

Eric Hanson eric at pegasi.net
Thu Jan 1 02:34:23 EST 2004

```I'm coming to this from an information systems perspective.  The human
body is arguably the most complicated information system on the
planet.

There is a problem in computer scientist called the Traveling Salesman
Problem (TSP) that is one of the greatest unsolved problems in
mathematics/comp. sci.  I'm exploring a theory that the human body
seems to solve this problem.

The traveling salesman problem states that a traveling salesman wants
to visit for example the 50 capital cities of the US starting and
ending in Salem, and travel the shortest route between them all.
Where does it go first from Salem?  Where after that?  Finding the
optimal solution by trying all possible combinations is a simple
algorighm but the number of solutions increases exponentially and
after just a few cities it becomes computationally unfeasible to use
this method.  People trying to "solve" the traveling salesman problem
are looking for an algorithm that finds the optimal solution much
faster than the brute force method, namely in polynomial time.

To rephrase, the TSP deals with a problem where there are many nodes
(cells) in a graph (body) and in order for a single node to know who
its neighbors are as indicated by the shortest route through all
paths, it has to have a bird's eye view of the entire graph and know
the shortest route through it.  This seems to parallel what the human
body does because for a single cell to know what piece of a liver it
should be it needs to know its place in the entire liver and the
entire body for that matter, or at least that's the theory I'm
exploring.

So a cell divides and the new cell starts expressing different genes,
but maybe someone can answer me this.  _Where_ does it get the
information to know which genes to express?  Is it from the cell it
divided from, or from the extracellular cues or ...?  If the answer is
too complicated or if it's just not known yet, is there a term for
this area of study or you could point me more specifically towards
something?

Thanks,
Eric

R.Jayakumar at RoswellPark.org ("Jayakumar, R") wrote in message news:<97101976F8A044468CA74FE11883B90E020489A0 at VISTA.roswellpark.org>...
> Even though all cells contain the same set of genes (genes are pieces of
> DNA which expresses RNA which translates into proteins), not all genes
> are expressed in all cells.  Through a complicated system of gene
> regulatory elements very early in the cell differentiation pathway,
> cells get specialised and channelled into particular duties.  Hence only
> particular genes necessary for the specific function of each cell type
> (which comprises a specialized tissue like the muscle or tonail) are
> turned on in that cell while the other genes are more or less silent or
> silenced.
>      If you need to know more about that, you have years of molecular
> biology to learn.  ACtually most of molecular biology and cell biology
> deals exactly with what you just asked. :-)))  If everybody knew exactly
> how cells function, we wouldn't have cancer or a host of other medical
> diseases anymore.  But we are working towards it. :-))

```