A genetic mapping conundrum

Michael Prigge prigge at umich.edu
Sat Oct 7 20:41:10 EST 2000

We generally do as this other person did and only score homozygous
recessive individuals.  This allows scoring of 2 chromosomes per F2
individual without having to grow up the F3 progeny to distinguish +/-
from +/+ individuals.  In practice, I have scored ~20 WT F2s to guard
against weirdnesses that might theoretically arise.  If you can be sure
that the phenotype segregates in a truly Mendelian fashion beforehand,
then I can't imagine a good reason to score every individual unless the
number of F2 progeny available is a limitation.
In article <st2153-0610001718590001 at z147.zi.biologie.uni-muenchen.de>,
st2153 at zi.biologie.uni-muenchen.de (Gregor Bucher) wrote:

> Hi Jim!
> I guess the only reason for looking for homozygotes only is, that often
> (depending on the mutation) the heterozygotes are not distinguishable from
> wildtype in terms of phentype - and you say he is dealing with recessive
> mutations (which, by definition do only show a phenotype in the homozygote
> state)
> Do you agree or did I get something wrong with the problem?
> Gregor
> (another "mapper")
> >chromosome. Here is the question: in my reading of the literature, I came
> >across one researcher who ONLY analyzed the F2 homozygous recessive mutants
> >for linkage to the polymorphic DNA markers-- is this a legitimate way of
> >mapping a gene or should you be analyzing ALL your segregants for linkage?
Michael J. Prigge                    phone  (734) 647-4153
Dept. of Biol., Univ. of Michigan      fax  (734) 647-0884
830 N. University
Ann Arbor, MI 48109-1048

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