Hybridization of DNA's from Neurospora crassa strains may indicate base sequence alterations as a consequence of genetic transformation.

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 revertant 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 revertant 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.