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A Maize Genetic Question

Peter A Peterson pap at iastate.edu
Tue May 2 09:42:34 EST 2000

	Rather than increased recombination in successive 
backcrossing, could it be that the 1-2 cM in the original SSR was 
impeded in recombination. Thus, if possible, and you could do it, 
would an in situ hybridization with your SSR show a "bulge" in the 
pairing. In the early days (early 1980's of molecular effort), 
unexpected inserts were found residing adjacent to genes. (See the 
Schwarz-Sommer et al paper --EMB0 J. 3:1021, 1984) for a case of a 6 
kb insert adjacent to the wx gene.   PAP

At 03:31 AM 5/2/00 +0100, you wrote:
>Here is a genetic mystery (to me at least),
>	I now know of two cases where individual researchers have
>identified an SSR within 1-2 cM of their gene of interest.  These closely
>linked SSRs were identified in progeny of a self following an outcross to
>B73.  Upon repetitive backcrossing to B73, the SSR gets genetically farther
>and farther away; in one case going from 1 cM to ~25cM in one generation-
>statistically significant with a chi-squared test.  What is happening here?
>Have people who use marker-assisted breeding seen this?  At first, I
>thought it was a mistake, but with two independent cases, and all numbers
>checked for statistical significance, I think it is real.  Do rates of
>recombination change with increased homozygosity (a hard thing to measure)?
>	Thank you for your help!
>Lisa Harper
>Cande Lab
>Department of Molecular and Cell Biology
>345 LSA
>University of California
>Berkeley, CA 94720-3200

Peter A. Peterson
Agronomy Department
Iowa State University
Ames, Iowa 50011
OFFICE: [515] 294-9652
FAX: [515] 294-2299
pap at iastate.edu

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