Acta Biologica 30. (1979)

4. szám - Fehér Zs.–Schablik M.–Szabó G.: Hybridization of DANN's from Neurospora crassa strains may indicate base sequence alterations as a consequence of genetic transformation

Acta biol. Acad. Sei. hung.. 30 (4), 387 392 (1979) HYBRIDIZATION OF DNA’S FROM NEUROSPORA CRASSA STRAINS MAY INDICATE BASE SEQUENCE ALTERATIONS AS A CONSEQUENCE OF GENETIC TRANSFORMATION Zs. Fehér, Marcella Schablik and G. Szabó INSTITUTE OF BIOLOGY, UNIVERSITY MEDICAL SCHOOL, DEBRECEN, HUNGARY (Received 1979—10 23) Abstract Deoxyribonucleic acids of Neurospora crassa strains involved in genetic transfor­mation experiments were studied by means of DNA-DNA hybridization. No significant difference was detected in the extent of hybridization reassociating 32P-DNA of an ino­sitol-requiring recipient strain with an excess amount of unlabelled homologous DNA and that of the transformed, spontaneous revenant and wild-type strains. Studies on the thermal stability of hybrids revealed 1.2—1.7% heterology between the recipient and transformant DNA’s. The spontaneous revenant and wild-type strains proved to be ho­mologous with the recipient strain. We suppose that the heterology we measured is the result of the alteration of the nucleotide sequences caused by the multilocal integration of transforming DNA into the recipient genome. Introduction The possibility of genetic transformation in Neurospora crassa has been intensely investigated [13, 14, 2]. In some of these experiments an inositol­­requiring mutant of Neurospora crassa, R 2506-5-101 (ini, rg, mta) was treated with wild-type DNA yielding inositol-independent transformants. Spontaneous revertants without DNA treatment were also obtained. The comparison of transformant and revertant strains revealed differences in their growth rate, i. e. the growth rate of the transformed strains was signifi­cantly lower than that of the revertants [15]. These results can be explained by assuming the integration of transforming DNA into a number of chromosomal sites and thus causing mutations, which may be responsible for the decreased growth rate. This explanation is supported by MISHRA’S experiments, who detected osmotic mutants, leaky mutants, morphological changes and sterility as the results of DNA treatment [12]. The stability of the inl+ character obtained after DNA treatment has also been studied by crossing transformant, spontaneous revertant and stan­dard wild-type strains with an ini strain [15]. In the crosses of transformant strains, a large number of non-Mendelian tetrads (6 : 2, 2 : 6, 5:3 inl+ : ini) were obtained, while in the other crosses no such phenomenon was observed. Acta Riologica Academiae Scientiarurn Hungaricae 30, 1979

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