Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!umbc3!chiafari
From: chiafari@umbc3.UMBC.EDU (Mr. Frank Chiafari )
Newsgroups: sci.bio
Subject: Re: Are blood types inherited?
Message-ID: <2269@umbc3.UMBC.EDU>
Date: 30 Aug 89 17:10:43 GMT
References: <4250@orca.WV.TEK.COM> <661@lakart.UUCP>
Reply-To: chiafari@umbc3.umbc.edu.UMBC.EDU (Mr. Frank Chiafari (BIOL-GRAD))
Distribution: usa
Organization: University of Maryland, Baltimore County
Lines: 30



This is a response to many articles on the net which were close, but not
precisely correct. The ABO blood group marker systemm describes a red cell
surface antigen (the H-antigen) which can undergo modification by the addition 
of sugar moities to the protein structure. Either you possess the capacity to
modify the H-antigen (A1,A2,B,etc), or you don't(O), or your missing the H-
antigen altogether(O-bombay). The modification enzymes, represented as non-O
types, are co-dominant, meaning they can each be expressed without exclusion 
of the other types. These types are detected using purrified sera (with
antibodies) from individuals that are immuno-sensitized to a type. Therefore,
"A1" individuals can have antibodies to "B" types, or any other type they do 
not (generally) possess. The gene for the null enzyme activity, "O", i
recessive to all other types because it is the lack of activity; O-bomyay is
recessive to normal H-antigen.
	We inherit two copies of each gene (generally), one from each parent. 
Therefore, an individual who is typed as an "A" could haveither an AA g
genotype or an AO genotype (O-bombay is encoded at the locus that produces the
H-antigen, NOT at the locus that produces the modification enzymes).The case
you gave as an example indicates non-paternity unless both parents are hetero-
zygous at the H-antigen locus for O-bombay (one normal copy, one O-bombay), and
happened to give the child their O-bombay genes, making him homozygous, a VERY
unlikely event.
	If this was a real paternity case, other blood group or DNA markers 
could be tested to resolve the situation, looking for more exclusions. Remem-
ber however, that the results and interpretation are only as reliable as the 
test.

Wasn't that simple.