Archiver > GENEALOGY-DNA > 2004-09 > 1095445302

From: ellen Levy <>
Subject: Re: [DNA] What is the MC1R gene? (WAS The Irish are not celts, say experts)
Date: Fri, 17 Sep 2004 11:21:43 -0700 (PDT)
In-Reply-To: <008b01c49cd6$4ac0cbe0$3e6c8251@d6e4z6>

This discussion brings us back to the issue of skin,
hair & eye pigmentation. Despite the animal testing
in this next study, perhaps we can leave the orangutan
analogies behind in the discussion?

Here is an article of interest. I myself cannot access
it, but here's the abstract:

"The Melanocortin 1 Receptor (MC1R): More than Just
Red Hair," by JL Rees, University of Edinburgh, 2000,
in PubMed:

"The melanocortin 1 receptor, a seven pass
transmembrane G protein coupled receptor, is a key
control point in melanogenesis. Loss-of-function
mutations at the MC1R aare associated with a switch
from eumelanin to phaeomalanin production, resulting
in a red or yellow coat colour. Activating mutations,
in animals at least, lead to enhanced eumelanin
synthesis. In man, a number of loss-of-function
mutations in the MC1R have been described. The
majority of red-heads (red-haired persons) are
compound heterozygotes and homozygotes for up to five
frequent loss-of-function mutations. A minority of
redheads are, however, only heterzygote. The MC1R is,
therefore, a major determinant of sun sensitivity and
a genetic risk factor for melanoma and non-melanoma
skin cancer. Recent work suggests that the MC1R also
shows a clear heterozygote effect on skin type, with
up to 30% of the population harbouring
loss-of-function mutations. Activating mutations of
the MC1R in man have not been described. The MC1R is
particularly informative and a tractable gene for
studies of human evolution and migration. In
particular, study of the MC1R may provide insights
into the lightening of skin colour observed in most
European populations. The world wide pattern of MC1R
diversity is commpatible with functional constraint
operating in Africa, whereas the greater allelic
diversity seen in non-African populations is
consistent with neutral predictions rather than
selection. Whether this conclusion is as a result of
weakness in the statistical testing procedures
applied, or whether it will be seen in other pigment
genes will be of great interest for studies of human
skin colour evolution."

Ellen Coffman

--- AAF <> wrote:

> Red Hair, etc.
> At the risk of unleashing another round of furious
> exchanges: Orang-Utans
> also have red hair !
> Can there not be multiple origins for this. Is it
> not the case that African
> dark skin colour is from a dominant gene, but
> Australian aborigine dark skin
> colour is from a recessive gene?
> Alan Foster.
> > ****************
> > This might have been asked and answered before,
> > so if so, please respond to me off list.
> > What is the MC1R gene?
> > Does this gene show up in the jewish population
> > too.... they have red hair..... and if I'm not
> mistaken,
> > so do some Scandinavians.
> > And is this gene ALONE the cause of red hair?
> >
> > If you don't know, could someone else answer,
> > because I'm very interested in this, as I have
> > dark auburn hair and it runs in the family.
> > Thank you!
> >
> > Warm Regards from Maine,
> > Debby Reagan
> >
> >
> > ==============================
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