Another set of "unknowns" is HA2, HB2 and a diploid made by crossing HA2xHB2. The mating mixture produced by mixing HA2 and HB2 should be purified by streaking for single colonies on YED. (See Laboratory Methods) If the mating conditions are poor the single colonies produced may be a mixture of diploids and unmated haploids.
1st Day:
Yeast strains usually come from the supplier growing on agar
slants. Contamination may be a problem when students use the
master set of yeast strain slants as the source of their strains.
You may wish to subculture the strains on YED plates. One
subculture plate containing the tester strains and unknowns will
supply enough yeast for a class. If several groups need access
to the yeast at the same time, you may want to make several
subculture plates (See segment on Subculturing Yeast on video
tape III).
2nd Day:
You may wish to have the students make a paper grid to tape
on the bottom of the plate or they could draw a grid directly on
the bottom of the plate with a marking pen.
3rd Day:
Stress that a new sterile toothpick should be used for each
different strain and mixture.
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Last updated Friday July 11 1997