During the development of disomic additions of rye (Secale cereak L.) chromosomes to wheat (Triticum aestivum L.), two reverse tandem duplications on wheat chromosomes 3D and 4A were isolated. By virtue of their meiotic pairing, the reverse tandem duplications initiated the chromatid type of the breakagefusion-bridge (BFB) cycle. This BFB cycle continued through pollen mitoses and in the early ...

The B chromosome of maize has been used in a study of dicentric chromosomes. TB-9Sb is a translocation between the B and chromosome 9. The B-9 of TB-9Sb carries 60% of the short arm of 9. For construction of dicentrics, a modified B-9 chromosome was used, B-9-Dp9. It consists of the B-9 chromosome plus a duplicated 9S region attached to the distal end. In meiosis, fold-back pairing and crossing...

We have utilized a dihydrofolate reductase (DHFR) probe in combination with selected probes from other positions along the 2q chromosome arm in a two-color fluorescence in situ hybridization analysis of early DHFR gene amplification events in CHO cells. These studies show clearly that the most frequent initiating event is the formation of a giant inverted duplication, resulting from chromosome ...

OBJECTIVE This study was designed to investigate DNA damage and/or repair capability, non-random chromatid breakage, and p53 expression in patients with colorectal cancer. METHODS The bleomycin sensitivity assay was used in a case-control study to compare the DNA damage repair system between colorectal cancer patients and controls. G-banding was used to search for non-random chromatid breaks....

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...

Thymidine-H(3) of high specific activity was used to study the distribution of labeled chromatids during meiotic divisions in spermatocytes of a species of grasshopper (Orthoptera). The distribution is regularly semiconservative as has been shown previously for mitosis, i.e., all chromatids are labeled after incorporation of thymidine-H(3) into DNA at premeiotic interphase. If incorporation occ...

Sister chromatid exchange (SCE) frequency in chromosomes from lymphocytes of a patient with dyskeratosis congenita was 12-2 per mitosis. Our 33 normal controls had a mean of 5-4 SCE per mitosis and 5 patients with Fanconi's anaemia averaged 7-6 SCE per mitosis. The rate of chromosome breakage was only 0-5% in the dyskeratosis congenita patient and 0 to 2-5% in controls, while the Fanconi's anae...

Thyroid hormones stimulate aerobic metabolism which may lead to oxidative stress accompanied by damage to various cellular macromolecules, including DNA. Previous comet assay studies have shown that thyroid hormones cause DNA damage due to the creation of reactive oxygen species (ROS). However, cytogenetic studies have been equivocal because although an increase in the sister-chromatid exchange...

In the alternative pathway of telomere lengthening (ALT), neoplastic cell growth is prolonged by telomere recombination. We show that ALT is unexpectedly characterized by high rates of ongoing pericentromeric chromosomal instability. Combined with telomeric recombination, ALT pericentromeric instability generates neoacrocentric chromosomes. In the present studies, we describe a subgroup of ALT ...

BACKGROUND Use of a hookah (a type of water pipe) is a traditional way of smoking tobacco, particularly in the Middle East. In Turkey, its popularity has been growing in recent years, especially among young people. It is known that cigarette smoking has genotoxic effects and causes mutations, but no comprehensive study has been done on the genotoxic effects of hookah usage, particularly in Turk...