Dear Colin and Dave,
The sporulation problem in s288c could be due to one of those "common
markers", namely his3-delta200. If the diploid is homozygous for this
allele, it may not sporulate well due to reduced expression of PET56.
Check the bionet.molbiol.yeast archives for a discussion of PET56 and
his3-delta200 that occured in August. I would be happy to send you
PET56 on a plasmid to see if this helps. Marc Garten told me this
solved his sporulation problems.
Dept. of Biochemistry and Molecular Biology
University of Massachusetts
Amherst, MA 01003
email ksirum at biochem.umass.edu