Dm. Demarini et al., MOLECULAR ANALYSIS OF MUTATIONS INDUCED AT THE HISD3052 ALLELE OF SALMONELLA BY SINGLE CHEMICALS AND COMPLEX-MIXTURES, Environmental health perspectives, 101, 1993, pp. 207-212
More single chemicals and complex environmental mixtures have been eva
luated for mutagenicity at the hisD3052 allele of Salmonella, primaril
y in strain TA98, than in any other mutation assay. The development of
colony probe hybridization procedures and the application of the poly
merase chain reaction and direct DNA sequencing has permitted rapid mo
lecular access to this allele. We discuss these techniques and the res
ulting mutation spectra that have been induced by a variety of environ
mental mutagens and complex mixtures. A common GC or CG deletion withi
n a hot-spot region of the sequence dominates most of the spectra. In
addition to this two-base deletion, we have recovered about 200 other
types of mutations within the 72-base target for reversion of the hisD
3052 allele. These include a variety of deletions (as large as 35 base
s), duplications (as large as 46 bases), and complex mutations involvi
ng base substitutions. The quasipalindromic nature of the target seque
nce and its potential to form DNA secondary structures and slippage mi
smatches appear to be an important basis for the mutability of this al
lele.