[Induction of repetitive nucleotide sequences. The probable mechanisms of genome evolution and gene conversion]

In the preselected site of pBR322 plasmid DNA related to the Tcr gene mutations were induced by the complementary single-stranded DNA restricts carrying alkylating groups. The alterations of the DNA primary structure in the mutagenized site were studied. It was found and that in the majority of mutants with the impaired Tcr gene function, the tandem direct repeats appeared. The repeats of 7-8 base pairs were localized in a fixed site of the Tcr gene, downstream of the palindrome. It is suggested that tandem repeats appear as a result of D-loops formation when single-stranded DNA forms a hairpin structure, due to the presence of palindromes. In the light of this notion, the tentative schemes of gene conversion and genome evolution are discussed.