PMID:10323233
| Citation |
Uematsu, N, Matsuoka, C, Agemizu, Y, Nagoshi, E and Yamamoto, K (1999) Asymmetric crossing over in the spontaneous formation of large deletions in the tonB-trp region of the Escherichia coli K-12 chromosome. Mol. Gen. Genet. 261:523-9 |
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| Abstract |
The chromosomal tonB gene of Escherichia coli was used as a target for the detection of spontaneous deletion mutations. The deletions were isolated in both recA+ and recA- cells, and mutants carrying large deletions were identified because they also lacked part or all of the trp operon. The frequencies of tonB-trp deletion were 1.79 x 10(-9) and 1.09 x 10(-9) for recA+ and recA- cells, respectively. We analyzed 12 deletions from recA+ and 10 from recA- cells by cloning and direct sequencing. The deletions ranged in size from 5612 bp to 15142 bp for recA+ and from 5428 bp to 13289 for recA- cells. Three deletions from recA+ cells and five deletions from recA- cells were found to have occurred between short sequence repeats at the termini of the deletion, leaving one copy of the repeat in the mutant sequence. Seven deletions from recA+ cells and three deletions from recA- cells did not have repeats at their termini; in these cases, the DNA sequences that are adjacent to the deletion termini in the wild-type are characterized by short (2-4 bp) repeats. From these results, a model is presented for the generation of deletion mutations which involves formation of an asymmetric crossover mediated by repeated sequences of 2- to 4-bp. |
| Links | |
| Keywords |
Bacterial Proteins/genetics; Base Sequence; Chromosomes, Bacterial/genetics; Crossing Over, Genetic; DNA, Bacterial/genetics; Escherichia coli/genetics; Escherichia coli Proteins; Genes, Bacterial; Membrane Proteins/genetics; Mutation; Operon; Rec A Recombinases/genetics; Sequence Deletion; Tryptophan/genetics |
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