yeast mating

Michael Lichten lichten at HELIX.NIH.GOV
Mon Apr 24 08:09:37 EST 1995

Colin MacDiarmid writes:

>I need some help again from the newsgroup.  I have mated two isogenic
>haploids and want to isolate a diploid, but obviously have no selection
>for this.  I have read that mating tests distiguish a and alpha mating
>types in haploids by absence of growth i.e. halo on plates with the
>appropriate mating factor.  It seems to me from reading this that it could
>be possible to select a diploid from a mating mixture by streaking out on
>a plate containing both mating factors, to which only a diploid would be
>insensitive.  I realise this might not be a tight selection, but any
>significant difference in growth rate between haploid and diploid cells
>would be OK for me, since I'd do a sporulation test on probable diploid
>Does it sound feasible, has anyone tried this?  How much of the mating
>factors would I need to use?  (I dont have access to a micromanipulator,
>so can't pick out zygotes, as someone suggested I do). Any help would be
>greatly appreciated.

We have found that all you need to do is to mix overnights of the a and
alpha parents and spot the mix down on a YEPD plate.  After overnight
growth, half of the cells or more in the spot are diploid, so you can just
streak them out and test mating type (or sporulation) on a dozen or so
single colonies.

Michael Lichten
lichten at

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