[rat-forum] Re: [rat-forum] RE: A How much allelic pleomorphism is seen in an inbred strain?

David A. Blizard dab22 at hatteras.cdhg.psu.edu
Tue Mar 18 07:51:33 CST 2003

Dear Milt,

         Approx. 98% of the alleles in L-W rats are homozygous so the little residual heterozygosity that exists shouldn't hinder your mapping attempts.  The more important issue is selecting a suitable set of markers that are distributed throughout the genome and differ between Fischer(!) and L-W.  Perhaps the 400 you have typed already in L-W have also been typed in F-344 (See Rat Genome Database)..so that you can select a suitable set.  In general, the more polymorphic the strains that go into the cross, the easier it is to map your trait. If it turns out that F344 and L-W aren't very different in SSLPs that could be an issue. Indeed, if they are not sufficiently different from each other it might be worth choosing another non-susceptible strain that has a very different background.  Here, there are several strains that are differ genetically from most other strains (See Rat Genome database).

         Until you observe the occurrence of spontaneous and induced tumors in a segregating population you won't really know whether the genetics of either forms of tumor are simple  or complex (many genes).

         The only reason to be concerned about the residual heterozygosity in L-W is if those regions are linked to genes that play a role in the tumors you are interested in.  That seems highly unlikely but it's good to be aware of it.


David Blizard

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