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 × 10−9 and 1.09 × 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.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received: 14 September 1998 / Accepted: 22 December 1998
Rights and permissions
About this article
Cite this article
Uematsu, N., Matsuoka, C., Agemizu, Y. et al. 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, 523–529 (1999). https://doi.org/10.1007/s004380050996
Issue Date:
DOI: https://doi.org/10.1007/s004380050996