Immunoglobulin and T-cell receptor genes are assembled during lymphocyte development by a novel, highly regulated series of gene rearrangement reactions known as V(D)I recombination. All rearranging loci are flanked by conserved heptamer-nonamer recombination signal sequences. Gene rearrangement results in the imprecise fusion of coding sequences and the precise fusion of signal sequences. DNA molecules with double-stranded breaks near signal sequences have been detected in cells undergoing V(D)I recombination of the TCR8 locus. We have devised a ligation-mediated PCR assay that detects broken-ended molecules in purified genomic DNA. Using this assay we found that DNA breaks occurring precisely at the signal sequence-coding sequence junction are a general feature of V(D)I recombination, appearing in association with each type of rearranging immunoglobulin gene segment. We show that a significant fraction of these broken ends are blunt and 5'-phosphorylated. In addition, detection of these broken-ended signal sequences is dependent on the activity of RAG-1 and RAG-2, and is restricted to the Go/G1 phase of the cell cycle

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A statistical re-analysis is undertaken of 118 inductively coupled plasma spectrometry analyses of Romano-British glass specimens found in excavations at Colchester. There are four vessel types present, some of which are associated with chronologically distinct periods. Previous research has suggested little diference in the mean composition of direrent types. The present paper shows that there are interesting differences in the variation of compositions within types, with some showing much greater compositional stability than others. Some possible models to explain this phenomenon are discussed.

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