TABLE 1.

Viability data of constitutive and inducible E2F1 transgenic animals^a

E2F1 transgenic line	3-week-old mice		Embryos at E17.5
	Viabilityb	Observed/expected ratioc	Viability	Observed/expected ratio
TEF1-5 (Eμ-pp-E2F1)	32/151 (F2 and F3)	32/75 = 0.43	16/35	16/17 = 0.94
TEF1-21 (Eμ-pp-E2F1)	2/57 (F1)	2/28 = 0.07	NDd
TEF1-43 (Eμ-pp-E2F1)	1/26 (F1)	1/13 = 0.08	ND
TEF1-62 (Eμ-pp-E2F1)	2/10 (F1)	2/5 = 0.40	ND
Actin-Cre;+/R26E2F1;R26E2F1;+/Actin-Cre	30/181	30/45 = 0.67	ND

^aThe mice were genotyped by PCR or Southern blot analysis of tail DNA. Viability of 3-week-old mice and of embryos at E17.5 were determined. Embryonic analysis on founder lines TEF1-21, TEF1-43, and TEF1-62 were not determined, since these transgenic lines could not be maintained. For heterozygous Actin-Cre; R26E2F1;+ crosses, embryonic survival data were not determined.

^bNumber of mice that survived to 3 weeks of age (or E17.5)/total number of mice (or embryos).

^cObserved/expected ratio is the ratio of the observed number of mice (or embryos) that survived to the number of mice (or embryos) expected to survive.

^dND, not determined.