Thanks for all your rapid responses about sap3. For anyone out there who
cares I'll summarize what I learned: sap3 is a recessive mutation which
confers resistance to the drug sinifungin (which is rather nasty and no longer
commercially available). This marker was used in the Hartwell lab for strain
construction by random spores much in the same way that can1 and cyh2 are used.
One person wrote: "The sap3 mutation is S-adenosyl methionine permease." So I
guess that is the source of the drug resistance...?
As for my His segregation troubles, the minute I hit the "SEND" button on
my message I regretted it because I remembered that the ade3 mutation confers a
His- phenotype! Many of you also reminded me of that!
As David Friedman put it in his message to me: "It seems that your [my]
troubles are over!"
Thanks to everyone for your help!