Jl. Jiao et al., COMPARISON OF THE MOLECULAR CHARACTERISTICS OF LACZ TRANSGENIC MOUSE MUTATIONS DETECTED BY VISUAL AND POSITIVE SELECTION, Mutation research, 372(1), 1996, pp. 141-145
lacZ gene mutations in the transgenic Muta(TM)Mmouse can be detected b
y two different selection systems. While mutant frequencies recovered
by phenyl-beta-D-galactoside (P-gal) selection are comparable with tho
se obtained using 5-bromo-4-chloro-3-indolyl beta-D-galactopyranoside
(X-gal) as substrate for beta-galactosidase, there may still be differ
ences at the molecular level in the mutations detected by these two me
thods. Accordingly, we have examined a spectrum of mutants recovered f
rom the X-gal system by regrowing these mutants on the P-gal plates. A
ll colourless X-gal mutants grew normally on the P-gal plates. However
, 11 out of 53 single light blue mutants, which express partial beta-g
alactosidase activity, produce few or no plaques on the P-gal plates,
indicating the possible loss of some mutations using the positive sele
ction system. Further analysis of mutant phenotypes and base changes i
ndicates that such loss is not mutation-type specific. Our data sugges
t that the positive selection method can detect the majority of lacZ m
utations detectable by visual selection and is more efficient at detec
ting mutants within a reduced range of beta-galactosidase activity.