[Bioforum] Re: Adult human phenotype

Bob bbx107 at excite.com.XXXX
Mon Aug 1 23:15:37 EST 2005


On 1 Aug 2005 10:28:29 -0700, "Horus" <ggroups at blonz.com> wrote:

>Please forgive this question from a scientist in another field who is
>not that well versed in genetics.  My thinking was that the adult human
>phenotype, once defined, resists change.
>
>I realize that there are many facets to "phenotype" and we cannot
>change eye color or height, but there are other characteristics that do
>change.
>
>For example.   You have a full head of hair when an adult, but over the
>decades you lose that hair.
>

some people do, some do not.


>Has your phenotype changed over the decades?

That is simply a semantic point. Declare that phenotype is amount of
hair. Amount of hair changes, therefore phenotype changed.

This example, at least so far, does not fit your initial proposal, of
resistance to change.


>
>Example two:  You are overweight.  You attempt to lose weight and do
>everything according to prescription.   You keep gaining back the
>weight.
>
>Is this an example of an obese phenotype reexpressing itself?

yes


There are a couple of things particularly interesting about body
weight. With free feeding, a person's body weight may change very
little over, say, 50 years -- less than 1% average change per year,
without any conscious effort. Obviously the system is self-regulated,
and rather robust. But we also realize that different people have
different natural weight -- and that it is hard for an individual to
deviate much from that.



Not sure where you are going with this. But some characteristics are
tightly regulated. Much has been written about the robustness of
biochemical/metabolic pathways.


bob




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