A Y chromosome census of the British Isles.

The degree of population replacement in the British Isles associated with cultural changes has been extensively debated. Recent work has demonstrated that comparisons of genetic variation in the British Isles and on the European Continent can illuminate specific demographic processes in the history of the British Isles. For example, Wilson et al.

DNA repair gene Ercc1 is essential for normal spermatogenesis and oogenesis and for functional integrity of germ cell DNA in the mouse.

Ercc1 is essential for nucleotide excision repair (NER) but, unlike other NER proteins, Ercc1 and Xpf are also involved in recombination repair pathways. Ercc1 knockout mice have profound cell cycle abnormalities in the liver and die before weaning. Subsequently Xpa and Xpc knockouts have proved to be good models for the human NER deficiency disease, xeroderma pigmentosum, leading to speculation that the recombination, rather than the NER deficit is the key to the Ercc1 knockout phenotype.

Replication failure, genome instability, and increased cancer susceptibility in mice with a point mutation in the DNA ligase I gene.

DNA ligase I has a key role in DNA replication in the joining together of short replication intermediates. We used gene targeting to introduce a point mutation into the mouse DNA ligase I gene that was present in a human cancer patient with immunodeficiency and a cellular accumulation of DNA replication intermediates. Mutant mice grew more slowly and showed hematopoietic defects at critical stages at which the demands for DNA replication were highest.

Founding mothers of Jewish communities: geographically separated Jewish groups were independently founded by very few female ancestors.

We have analyzed the maternally inherited mitochondrial DNA from each of nine geographically separated Jewish groups, eight non-Jewish host populations, and an Israeli Arab/Palestinian population, and we have compared the differences found in Jews and non-Jews with those found using Y-chromosome data that were obtained, in most cases, from the same population samples. The results suggest that most Jewish communities were founded by relatively few women, that the founding process was independent in different geographic areas, and that subsequent genetic input from surrounding populations was limited on the female side. In sharp contrast to this, the paternally inherited Y chromosome shows diversity similar to that of neighboring populations and shows no evidence of founder effects.

DNA ligase I null mouse cells show normal DNA repair activity but altered DNA replication and reduced genome stability.

DNA ligase I is the key ligase for DNA replication in mammalian cells and has also been reported to be involved in a number of recombination and repair processes. Our previous finding that Lig1 knockout mouse embryos developed normally to mid-term before succumbing to a specific haematopoietic defect was difficult to reconcile with a report that DNA ligase I is essential for the viability of cultured mammalian cells. To address this issue, we generated a second Lig1 targeted allele and found that the phenotypes of our two Lig1 mutant mouse lines are identical.