TABLE 1.

Effect of HU treatment on lacZ inactivation

Expt no.	Without HU treatment			With HU treatment
	No. of blue colonies	No. of white colonies	% Inactivationa	No. of blue colonies	No. of white colonies	% Inactivationa
1	253	16	5.9	131	17	11.5
2	194	19	8.9	103	24	18.9
3	207	18	8.0	92	15	14.0
4	149	21	12.4	59	15	20.3
Avg			8.8			16.2
SD			2.7			4.1

^a% Inactivation was determined by dividing the number of white colonies by the total number of colonies and multiplying by 100.