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ilv1 mutants failing to grow on defined media

Beth A. Montelone bethmont at ksu.edu
Tue Jan 14 15:40:17 EST 1997

Michael Lichten wrote:
> For reasons that are best left unsaid, we (we=Alastair Goldman) have
> created a hybrid yeast strain that is mostly cerevisiae (SK1 background)
> but which carries a chromosome V from carslbergensis.  This chromosome V
> is marked with an ilv1- mutation.  The strains we are using are usually
> leu2- and arg4-.
> The problem we're having is that these strains grow poorly (very poorly)
> on defined complete media (SC), even when supplemented with the
> recommended amounts of isoleucine and valine (30 ug/ml and 150 ug/ml,
> respectively).

I don't know what the problem is but here are two (perhaps fairly
obvious) ideas:

1) the carlbergensis chromosome V carries another auxotrophic marker for
something not normally added to SC.

2) ilv1 mutants only require isoleucine, not valine.  By adding valine,
you may be screwing up some complicated regulatory mechanism.  See the
Jones and Fink article in the original CSH yeast book if you really want
to know what a complicated mess this is.  So I would try it with only
isoleucine added (ie. minimal plus isoleucine plus leucine and

Beth Montelone

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