unusual inheritance of disease susceptibility

Ulrich Beutner ubeutner at isrec-sun1.unil.ch
Tue Jun 20 17:43:54 EST 1995

Grant Morahan (morahan at wehi.edu.au) wrote:
: Hello,

: We have been analysing genetic susceptibility to an experimentally-induced
: disease in mice.  The results are surprising. 
: Inbred strain A -100% susceptible;
: inbred strain B -100% resistant. 
: (AxB)F1  - 50% are susceptible.  
: F2 -  25% are susceptible. So far, so good.

: But 50% of the ((AxB)xA)BC1 mice develop disease.
: (We don't have results for the reciprocal BC yet). 

: The problem is that the BC doesn't seem more susceptible than the F1.
: Can anyone suggest a genetic model to explain these results? We haven't
: been able to come up with one.
: Any suggestions would be welcome.
: -Grant

: -- 
: Grant Morahan, Ph.D.
: The Walter and Eliza Hall Institute of Medical Research
: Parkville, Victoria

I am not big expert in genetics, I just recently got into this field. What
really makes me worry is your 50% in F1. By the book this has only a few 
x-linked (that would actually work nicely, but cannot explain the 25% F2)
otherwise sex linked (mitochondrial DNA, MMTV)
non-genetic reasons i.e. e.g. environmental, age

Otherwise is it possible that the parental strains are not homozygous?

Hope this might help
Ulrich Beutner
Ubeutner at isrec.unil.c

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