Date: Thu, 23 May 1996 11:03:46 -0600
Subject: ABO chemistry


I just remembered another reason to think that O came first.  

The A, B and O antigens are proteins on the surface of red blood
cells.  They are antigens [except O] because they can stimulate
immune response against them, if for instance A or B blood is given
to a different blood type.  Sometimes this happens between woman and
fetus, in utero.

A and B antigens are the same structure as O except for different
extra bits added on.  A and B genes are the same, not likely to be
created whole, but by small additions of DNA in the right place at
the end of the O gene.

There is a very rare gene at a separate location that can cause the A
or B bits to not be constructed, so that a person's blood looks/is
type O while their genes are type A/B.  [Once used on a soap opera to
raise doubts about paternity.]

But, I digress...

Lisa


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