Re: [MLUG - DISCUSSION] cloning

[Mike Miller <EMAIL:PROTECTED>]

On Thu, 5 Oct 2006, Stephen Montgomery-Smith wrote:

> I think that just because there is a gene in your DNA doesn't 
> necessarily means it doesn't get 'expressed.'

Or that it does get expressed.

> Every cell in your body has the same set of genes, but they all perform 
> different functions. Thus by necessity there are complicated mechanisms 
> which say which genes get expressed and which don't.  These mechanisms 
> often are related to the environment, so for example, what part of the 
> body they are in (which they can tell by which 'homeobox' proteins are 
> present), or also to the internal state (i.e. a blood cell will split 
> into two blood cells no matter where it is).
>
> Thus even in a broader sense, certain genes might or might not be 
> triggered by external events.  I am told that this is conjectured with 
> Schizophrenia. It is a genetic defect, but it is only expressed if the 
> unborn baby gets a certain type of flu virus in the womb.  Once this has 
> happened, the symptoms are bound to appear in the teens or early 
> twenties.  But in of itself, the presence of the gene does not guarantee 
> the person will get Schizophrenia.
>
> I have read some about all this.  The mechanisms are many and varied, 
> and many not all that well understood - all in all it is a very exciting 
> and fast moving area of research - much is known, and yet much much more 
> yet to be known.

It's all very complicated.  We know that genes can have the same sequence 
but have different effects in different people because transcription is 
controlled by other sequences outside the gene and those regulatory 
sequences may be different.  The environment also plays a regulatory role. 
People talk about that a lot these days but it has been known forever.

Mike

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