The ability of our cells to maintain genomic integrity is fundamental for protection from cancer development. Central to this process is the ability of cells to recognize and repair DNA damage and progress through the cell cycle in a regulated and orderly manner. In addition, protection of chromosome ends through the proper assembly of telomeres prevents loss of genetic information and aberrant...

Laboratory and clinical studies suggest that genetic change is intrinsically involved in the development of cancer and that this change occurs in humans throughout carcinogenesis, in both early and late stages. Therefore, the quantification of the level of genetic change in human epithelial tissues may serve as a marker for cancer risk. The micronucleus test has been used to quantify the level ...

HE modification of a mutation rate induced by X-radiation has been T effected only in Drosophila where the use of low temperatures has been instrumental in significantly raising the rate of recessive lethals (MEDVEDEV 1935; KING 1947), a finding which, however, does not have the support of all investigators in this field (see KING 1947). Should the data of KING and others be further substantiat...

Eight X-linked recombination-defective meiotic mutants (representing five loci) and 12 X-linked mutagen-sensitive mutants (representing seven loci) of Drosophila melanogaster have been examined cytologically in neuroblast metaphases for their effects on the frequencies and types of spontaneous chromosome aberrations. Twelve mutants, representing five loci, significantly increase the frequency o...

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by predisposition to hematopoietic malignancy, cell-cycle checkpoint defects, and ionizing radiation sensitivity. NBS is caused by a hypomorphic mutation of the NBS1 gene, encoding nibrin, which forms a protein complex with Mre11 and Rad50, both involved in DNA repair. Nibrin localizes to chromosomal sites of ...

CK2 was the first protein kinase identified and is required for the proliferation and survival of mammalian cells. Here, we have identified an unanticipated role for CK2. We show that this essential protein kinase phosphorylates the scaffold protein XRCC1 and thereby enables the assembly and activity of DNA single-strand break repair protein complexes in vitro and at sites of chromosomal breaka...

Replication fork reversal protects forks from breakage after poisoning of Topoisomerase 1. We here investigated fork progression and chromosomal breakage in human cells in response to a panel of sublethal genotoxic treatments, using other topoisomerase poisons, DNA synthesis inhibitors, interstrand cross-linking inducers, and base-damaging agents. We used electron microscopy to visualize fork a...

Since the first description of human fragile sites (FS) more than 40 years ago, a variety of substances were reported to induce chromosomal breaks at non-random, breakage-prone regions. According to information available from human genome browsers aphidicolin, an inhibitor of DNA replication induces 77 of 88 known common FS. However, in the literature additional FS are reported, which are also,...

Male gametogenesis was cytologically analyzed in wheat lines homozygous or hemizygous for gametocidal (Gc) factors with different modes of action. The first and second meiotic divisions in all lines were cytologically normal. The postmeiotic mitoses were normal in the homozygous lines; however, chromosome fragments and bridges were observed in the mitoses of the hemizygous lines. The morphology...

ATURAL populations of many species of Drosophila show chromosomal N p o l ymorphisms, maintained presumably by superior fitness of the heterokaryotypes. Because inversions suppress the recombination in structurally heterozygous chromosomes, they may keep together the coadapted gene complexes inside, and in the vicinity of the inverted sections. This view is supported by the €act that in experim...