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human genome question

SA nospam at nospam.net
Thu Jun 14 01:05:35 EST 2001


In article <zgQV6.32302$s12.800204 at typhoon.mw.mediaone.net>,
 "Richard Norman" <rsnorman at mediaone.net> wrote:

> "maxwell" <mmmaxwell at hotmail.com> wrote in message
> news:9g85o8$7dkdc$1 at ID-81739.news.dfncis.de...
> >
> > Sascha Vynograd <vyn at domestic.de> wrote in message
> > news:9g7uae$e6g$1 at riker.addcom.de...
> > > What does it mean , that human genome is completly decoded?
> >
> > That the material it is made of has been mapped out, from one end to
> > the other.
> >
> > > Is my genome equivalent with others ?
> >
> > Not exactly, because there are huge numbers of places where differences
> > between individuals can be found.
> >
> > > What makes people different?
> > > differences gene expression or differences in genome?
> >
> > Both of the above, plus parts of the differences in gene expression
> > are due to experiences of the organism, both of the living person,
> > and also of factors within the cell that carry messages to and from the
> > genome,
> > and of factors within the cytoplasm of the zygote.
> >
> > (non-exhaustive..offered as examples; over-simplified, and with
> > implicit regard of interactive causalities)
> >
> 
> Just a few more details -- the human genome is not really completely
> decoded.  But probably all the parts that really count have been.
> There are technical reasons why two particular regions of each
> chromosome can't be decoded but these regions almost certainly
> don't code for any genes.  And what we have now is still called a
> "draft".
> 

Another important reason it is called a draft is because many genes have 
not even been identified as genes in any way. The human genome has been 
sequenced, it hasn't really been decoded by more than about 10%. To me 
decoded means you actually know what gene is there and what the products 
are. Technically speaking a gene hasn't been characterized until it has 
been cloned, and some would say, expressed in a non-expressing cell-line 
to show the product(s).  We are many years away from that since this has 
only been done for a few thousand genes...

As far as what makes people different, the poster is exactly right, but 
what is also amazing is how much is conserved, not only across humans, 
but even across species. By and large, we are the same, but very small 
differences in genes and large differences in gene expression combined 
with experience account for individual differences.  The reason we are 
mostly the same is because when a change in a gene offers a selective 
advantage (even a small one) it rapidly spreads (by natural selection) 
to the entire population and becomes "fixed" in a homozygous state. 
Interestingly, a small number of genes have different forms 
(polymorphisms) that dont seem to offer much advantage and can stick 
around and be stable... many other genes are toxic in a homozygous state 
(one reason inbreeding is so bad for you) and there is a strong 
selective advantage to having two different copies of some alleles.

anyway, we are in for some exciting times. More striking than the human 
genome project is our new-found ability to manipulate and replace genes 
using dozens of techniques that have mostly been developed in the last 
12 years. While most of this technology works best in mice right now, 
much of it may be plausible in humans in a few years.




> In general, two people differ in about 0.1% of their DNA.  That is one
> out of 1000 base pairs may differ. So perhaps 3 million out of the 3
> billion bases differ between individuals.  The work is just barely getting
> started on cataloging these differences.  Trying to understand just what
> the differences actually mean is still far away (except in a few exceptional
> cases).
> 
>




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