TABLE 2.

[PSI⁺] reduces [URE3] mitotic stability^a

Starting strain	% of cells from:
	YPAD plates		Plates without adenine
	[URE3]	[ure-o]	[URE3]	[ure-o]
[PSI+][URE3]	99.1	0.9	96.7	3.3
[psi−][URE3]	100	0	NDb	ND

^a[URE3] cells from USA plates were grown to colonies on YPAD plates, suspended in water, and spread onto YPAD plates or plates lacking adenine. At least three times, three 1-mm colonies from each of the latter plates were pooled, suspended in water, and spread onto YPD. The resulting colonies were scored for [PSI⁺] and [URE3] on the basis of color and size (see text) and verified as described in Materials and Methods. For [PSI⁺] and [psi⁻] starting strains grown on each medium, about 1,200 and 100,000 colonies were scored, respectively.

^bND, not determined.