ISSN:
1617-4623
Keywords:
Key wordsEscherichia coli
;
Deletion mutant
;
Illegitimate recombination
;
Repeated sequence
;
Asymmetric crossover
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004380050996
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