ture yielded 15 additional cases of dicentric Y chromosomes. Among the cases, a wide range ofvariation in phenotype, external genitalia, histology, and chromosomal findings was observed. Factors possibly contributing to such variability are discussed and include: the exact site of breakage and exchange in the Y chromosome; the timing of dicentric formation (meiotic vs mitotic); the occurrence o...

Nonreciprocal translocations and gene amplifications are commonly found in human tumors. Although little is known about the mechanisms leading to such aberrations, tissue culture models predict that they can arise from DNA breakage, followed by cycles of chromatid fusion, asymmetric mitotic breakage, and replication. Mice deficient in both a nonhomologous end joining (NHEJ) DNA repair protein a...

DNA breakage is intimately associated with meiotic recombination in the fission yeast Schizosaccharomyces pombe. Sites of prominent DNA breakage were found approximately 25 to approximately 200 kb apart in the genomic regions surveyed. We examined in detail a 501 kb region of chromosome I and found six sites, or tight clusters of sites, at which approximately 2%-11% of the DNA accumulated break...

ORK on recessive lethal mutation in Drosophila sperm has suggested ways win which chromosome breakage may be related to recessive lethal mutation, through position effect, deficiency, and as a direct result of breakage. The increase in aged oocytes of radiation-induced dominant lethals (PARKER 1959) and of rearrangement, the slower rejoining of breaks (PARKER and HAMMOND 1958) , and the higher ...

Genome integrity relies on precise coordination between DNA replication and chromosome segregation. Whereas replication stress attracted much attention, the consequences of mitotic perturbations for genome integrity are less understood. Here, we knockdown 47 validated mitotic regulators to show that a broad spectrum of mitotic errors correlates with increased DNA breakage in daughter cells. Une...

The cytokinesis-block micronucleus assay is a sensitive and simple indicator of chromosome damage, both chromosome loss and chromosome breakage, which also provides information on cell cycle progression and cytotoxicity. It was introduced in 1985 and has been successfully employed in many laboratories on different cell types to monitor exposed population, to identify mutagen-sensitive individua...

We present data that demonstrate that three MR elements isolated from wild populations of Drosophila melanogaster on two continents can cause large deletions of the X chromosome in males. The deleted chromosomes, termed mini-X chromosomes, are induced at a frequency of approximately 1:4000 in chromosomes that are initially free of P elements. In situ hybridizations using a cloned P sequence as ...

Although the underlying mechanism for these chromosomal alterations is unclear, it is possible that chromosomes with large constitutive heterochromatin bands such as chromosome 1 may be at risk of centromeric instability and be predisposed to centromeric fusion with other chromosomes. This possibility is supported by observations that unbalanced chromosome rearrangements frequently involve the ...