Text 3, 142 rader
Skriven 2004-09-09 17:43:00 av Anon. (1:278/230)
Ärende: Re: "crime gene"-was it f
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Michael Ragland wrote:
> Michael Ragland wrote: 
> Anon. <bob.ohara@sod.off.spammers.helsinki.fi> wrote or quoted: Tim
> Tyler wrote: 
> 
> TT: As he says, his interpretation is an "absurdity". But Gould is 
> attacking a straw man of his own making. Noboby using the "gene for X"
> terminology was ever asserting that single genes determined behaviour -
> and Gould should have been aware of that. 
> 
> BO: But is the general public aware of that? I suspect not - which is 
> why things like the "gay gene" get so much prss attention. Given that
> most people will interpret statements about a "gene for X" in a literal
> way, I think Gould was quite right to attack the absurdity - it's a
> straw man for geneticists, but not for the press and public. 
> 
> TT: I don't see anything wrong with a completely literal
> interpretation: A "gene for trait X" doesn't mean that no other 
> factors are involved - any more than a "vote for candidate X" means tht
> there are no other factors influencing the election result. The word
> "for" simply doesn't mean the same as "determines". 
> 
> MR: I think making an analogy between a "gene for trait X" and 
> "politics" is poor and sloppy form. To use a similar analogy would be to
> state a "gene for trait X" doesn't mean that no other factors are
> involved - anymore than "preparing and baking homemade lasagna" means
> that there are no other ingrediants influencing its composition. I see
> plenty wrong with a completely literal interpretation of a "gene for
> trait X". First of all with few exceptions there are no single "genes"
> for particular traits. So why you cling on to the idea of "gene X for a
> trait" as a completely valid literal interpretation is perplexing to me. 
> 
> BO:
> I think you're missing a pragmatic point: that we have to describe and
> discuss science. You do find genes that have large effects, i.e. if you
> compare individuals which are genetically identical except for the
> presence of the gene, then there are clearly observable differences. 
> 
> MR:
> Can you list some examples of a "gene" which has large effects if you
> compare individuals which are identical twins except for the presence of
> a "gene". 

GFP: Green Fluorescent Protein.  Roundup resistance is another.  Oh, and 
GUS (a Golden Oldie!).  Basically, look at any transgene.

If you are comparing the presence or absence of a "gene"  in a
> "genetically identical twin" then of course it is going to appear it has
> large effects because you're comparing it to an otherwise genetic
> replica. If you compared that same "gene" to a pool of genomes of
> non-identical twins you might find it wouldn't have as large effects
> because then you've introduced more genetic diversity and aren't dealing
> with primary natural clones. 

Again, GFP provides a good counter-example.  You can make comparisons 
across species.  Come to that, the same goes for many other transgenes.

A lot of genes _are_ stable across genetic backgrounds.  mlo was first 
discovered in Denmark when Danish barley breeding lines (their Carlsberg 
lines!) were irradiated.  Before they could get the gene into commercial 
production, it was found in a wild Ethiopian barley, which was certainly 
not a Carlsberg line.

<snip>
> 
> BO:
> And these are repeatable in different genetic backgrounds (GFP - green
> fluorescent protein - springs to mind). It is impractical not to talk
> about these as genes "for" a particular trait. 
> 
> MR:
> Well here we're not talking about the observable single "gene"
> differences between identical twins due to the presence of a "gene" in
> one and not the other. 

No, twins didn't come into this.  We were discussing the idea of a "gene 
for trait X".  Neither was any specific organism mentioned, so 
restricting it to humans is shifting the goal-posts.

<snip>
> 
> BO:
> I think this is OK as long as the gene creates the described effect
> stably (i.e. without too much environmenal or background genetic
> modification of phenotype), and if the primary function of the gene is
> to create the described phenotype.
> 
> MR:
> Yeah, I think GFP is a good example of that.
> 
> BO:
> For example, Mla is a barley gene for resistance to mildew, because it
> is involved in triggering a specific reaction that leads to a resistance
> response. 
> 
> The problem with talking about a gene for a trait is when it is not the
> primary function of the gene, but a side effect. For example, the mlo
> gene also confers resistance, but this appears to be a side effect,
> because its primary role seems to be in inhibition of a resistance
> reaction (i.e. it stops the barley from getting too jumpy and reacting
> to anything). I would therefore not describe it as a gene for
> resistance, even though it's jolly effective at it. 
> 
> MR:
> Interesting. But how did this specific reaction evolve? It's primary
> role seems to be an inhibition of a resistance reaction yet
> interestingly this leads to a resistance response. I think this shows
> how complex even a barley gene is.
> 
Not the gene, but the physiology and its interaction with the 
environment.  The reaction that mlo inhibits is a general one, so with 
the mlo phenotype the barley is responding to a lot of stimuli.  This is 
dis-advantageous, unless most of the stimuli are worth responding to, as 
they are when you have a large monoculture that produces a lot of 
mildew, which then provides many of the stimuli.

It all makes sense, especially to the plant.

Bob

-- 
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax:  +358-9-191 51400
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org
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