Rh- factor

David Adler dadler at u.washington.edu
Thu Aug 18 00:16:22 EST 1994

In article <CuoxsH.8uE at freenet.carleton.ca> ah335 at FreeNet.Carleton.CA  
(Glen Ashton) writes:
> A medical doctor claims that two Rh+ parents (i.e. blood type) cannot
> have a Rh- child.  From the few sources I have been able to find that
> talk about this it seems this is false, though I would appreciate if one
> could either confirm this, or even better, let me know of a definite
> source on this issue that I could refer the doctor to.


In article <9408171848.AA27866 at mendel.llnl.gov> greg at MENDEL.LLNL.GOV  
> This question can be answered fairly easily by checking the Online 
> Mendelian Inheritance in Man (OMIM) database ; in this case, look
> up entry 268150. 

Funny but I read the question and immediately thought 'check OMIM' and  
then read Greg's response and thought 'ok another question taken care  
of...' But realized I wasn't quite sure of the answer - I guessed Rh-  
(rh/rh) child is possible from parents who are both Rh+ if parents are  
heterozygotes (Rh/rh). Upon reading the OMIM entry I found the situation  
more complex - a multiple allele system with as yet unresolved genetic  
questions. Good reading but in fact does not answer the original question,  
at least not directly and simply. So I turn to the first genetics book  
that falls off my shelf, this ones a little dusty:

Principles of Genetics, Sinnot, Dunn and Dobzhansky, 5th edition, 1958,
page 119:

"...Thus where a child is cde/cde (r/r), although neither parent is, both  
parents must be heterozygous for this allele as in the mating  
[CDe(R1)/cde(r)] x [cDE(R2)/cde(r)]."

So parents that are both "Rh+" *can* have an "Rh-" child. Curious about  
the sources on which the medical doctor's claim is based. Interesting also  
in this exploration is that the issues discussed in the 1958 text remain  
unresolved in the OMIM entry.
David A. Adler                  Pathology SM-30
University of Washington        Seattle, WA 98195
(206) 543-0716 (phone)		(206) 543-3644 (fax)
"Science is nothing but trained and organized common sense"

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