Age constraints for the Trachilos footprints from Crete.

We present an updated time frame for the 30 m thick late Miocene sedimentary Trachilos section from the island of Crete that contains the potentially oldest hominin footprints. The section is characterized by normal magnetic polarity. New and published foraminifera biostratigraphy results suggest an age of the section within the Mediterranean biozone MMi13d, younger than ~ 6.

The meiotic recombination hot spot ura4A in Schizosaccharomyces pombe.

The meiotic recombination hot spot ura4A (formerly ura4-aim) of Schizosaccharomyces pombe was observed at the insertion of the ura4+ gene 15 kb centromere-proximal to ade6 on chromosome III. Crosses heterozygous for the insertion showed frequent conversion at the heterology with preferential loss of the insertion. This report concerns the characterization of 12 spontaneous ura4A mutants.

Creation and repair of specific DNA double-strand breaks in vivo following infection with adenovirus vectors expressing Saccharomyces cerevisiae HO endonuclease.

To study DNA double-strand break (DSB) repair in mammalian cells, the Saccharomyces cerevisiae HO endonuclease gene, or its recognition site, was cloned into the adenovirus E3 or E1 regions. Analysis of DNA from human A549 cells coinfected with the E3::HO gene and site viruses showed that HO endonuclease was active and that broken viral genomes were detectable 12 h postinfection, increasing with time up to approximately 30% of the available HO site genomes. Leftward fragments of approximately 30 kbp, which contain the packaging signal, but not rightward fragments of approximately 6 kbp, were incorporated into virions, suggesting that broken genomes were not held together tightly after cleavage.

A modified single-strand annealing model best explains the joining of DNA double-strand breaks mammalian cells and cell extracts.

The joining of DNA double-strand breaks in vivo is frequently accompanied by the loss of a few nucleotides at the junction between the interacting partners. In vitro systems mimic this loss and, on detailed analysis, have suggested two models for the mechanism of end-joining. One invokes the use of extensive homologous side-by-side alignment of the partners prior to joining, while the other proposes the use of small regions of homology located at or near the terminus of the interacting molecules.

An analysis of interference in the fission yeast Schizosaccharomyces pombe.

The evaluation of three-point crosses at the tetrad and random spore level leads to the conclusion that both chiasma and chromatid interference are absent in the fission yeast Schizosaccharomyces pombe.