With the applied aqueous suspensions of ABN low frequencies of fragments (mean frequency 0.54%) and diverse frequencies of clumped chromosomes were noticed. Nonrepetitive results in the control of the AIlium test with ABN suspensions were probably due to a nondefined amount of ABN around the roots. This could be avoided by using the saturated ABN solution with a constant concentration of ABN (10 tzg/ml) which could persist for a longer period of time.
85 Podstavkov~, S., E. Miadokov~ and D. Vl6ek, Department of Genetics and Molecular Biology, Bratislava (Czechoslovakia)
promoter from Tr-DNA or the promoter P35 from CaMV, and transferred into the genome of yellow green tobacco Nicotiana tabacum var. Xanthi. The expression of ada gene was measured in transgenic kanamycin-resistant plants or calluses by the activity of its product DNA alkyltransferase (AT) in the in vitro assay. Quantitative differences in AT activity were detected among independently transformed tobacco clones carrying the same promoter and among extracts from various tissues and cells of the same clones. Expression of the ada gene in various plant tissues and organs seemed also to be influenced by the type of promoter. No AT activity was detected in parental, nontransformed plants and in transgenic plants having the ada gene in the opposite direction.
Repair-deficient mutants of Chlamydomonas reinhardtii
VII. New assays in mutation analysis
Seven new UV-sensitive mutants with dark-repair damage were isolated in our laboratory. After their detailed analysis it was found that 5 of them were simultaneously photorepair-deficient. Genetic analysis showed that this simultaneous damage was monogenically determined. Data obtained showed a certain relation between darkrepair mechanisms and photorepair. The fact that photorepair is also involved in mutagenesis of this microorganism is evident from the different frequency of streptomycin-resitant mutants induced after UV-irradiation in two heteroallelic strains, Phr 1 and Phr 2.
86 Satava, J., I. Babfirek and J. Veleminskg, Institute of Experimental Botany, Czechoslovak Academy of Sciences, Prague (Czechoslovakia) Differences in the expression of E. coli ada gene in clones, organs and tissues of transgenic tobacco
The coding region (1.1 kb) of the DNA repair gene ada from E. coli was cloned into plant vectors carrying the selectable gene NPTII for kanamycin resistance and either the dual 1'-2'
87 Bronzetti, G., C. Della Croce, E. Morichetti, D. Rosellini and G. Soldani 1, Ist. Mut. e Diff., CNR, Via Svezia 10 and 1Lab. di Farmacologia, Ist. Patol. Spec. e Clin. Medica Veterinaria, V.le delle Piagge 2, Pisa (Italy) Genetic and biochemical studies on atrazine
Pesticides and their residues enter the biological food chain at various points and for varying periods. A number of reports are available concerning their ability to induce toxic and mutagenic effects in several biological systems. Atrazine is very widely used to control many broad-leaf and grass weed species in corn, sorghum, sugar cane, pineapple, and certain other crops. Studies on the genotoxic effects of atrazine in prokaryotic and eukaryotic systems show that it has no mutagenic activity. There is much information on the metabolite of s-triazines in plants, in the microsomal extracts of rat liver, in the soluble fraction of chicken liver homogenates, and in swine. In this work, atrazine was studied for its ability to induce genotoxic effects in the D7 strain of S. cerevisiae, using cells from the logarithmic growth phase, cytochrome P-450, and from the stationary growth