(DNA replication is sometimes said to be semidiscontinuous.)
These results were consistent with the semiconservative (but not the conservative) model of DNA replication.
Unscheduled DNA Synthesis | SpringerLink
Spermatogenesis is initiated at puberty and continues throughout a male’s lifetime. Once spermatogonial stem cells (which are undergoing mitosis every ~8 days in the mouse) are committed to becoming differentiating spermatogonia, they undergo a series of mitotic divisions before entering meiosis, which is then followed by a series of morphological transformations to produce mature, haploid, motile spermatozoa (Clermont 1972). These morphological changes occur as a wave from the outer germinal epithelial cells of the seminiferous tubules, leading eventually to translocation and release of spermatozoa into the lumen of the tubules, where they are transported to the caudal epididymus to await ejaculation via the vas deferens. In the latter phase of spermatogenesis, histones are replaced by protamines (a unique feature of the male germ cells) and the late spermatid/spermatozoa stages become DNA-repair deficient (Marchetti and Wyrobek 2005; Olsen et al. 2005). Thus, DNA damage incurred during these later phases of spermatogenesis can only be repaired using DNA repair machinery provided from the egg post-fertilization (Marchetti et al. 2007). Therefore, although alkylation of DNA can occur in these germ cell types, the processes that govern the formation of mutations and their inheritance in the offspring are fundamentally different from those arising in spermatogonia, and thus will be dealt with in a separate AOP.
DNA synthesisis a critical part of the life cycle of a cell:
It appears that the ability of genistein to reduce DNA synthesis may be whyit is a promising anti-cancer agent, for research suggests genistein cankill cancer cells and other drugs that reduce DNA synthesis kill cancer cells.
Unscheduled DNA Synthesis - Medical Abbreviations …
Bernstein, B. E., E. Birney, I. Dunham, E. D. Green, C. Gunter and M. Snyder (2012). "An integrated encyclopedia of DNA elements in the human genome." Nature 489(7414): 57-74.
As mentioned above, one motivation for developing this AOP is to address the current needs for improved testing in the field of germ cell mutagenesis. The recent release of the transgenic rodent mutation assay (TG 488) addresses this gap and is expected to be used more frequently in the future. In addition, new approaches that apply advanced sequencing technologies are expected to more fully assess the impact of environmental agents on induced heritable mutations and population health in the future. Finally, the lack of effective in high throughput mutation detection strategies, especially for germ cells, is a critical gap in this field. It is hoped that this AOP will provide a motivation to promote further research to address this gap, and serve as a basis to develop improved modelling approaches to predict whether a chemical agent is able to penetrate the testes and germ cells, alkylate DNA and cause heritable mutations.
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None of theother protein kinase inhibitors examined (herbimycin A, staurosporine,calphostin-C) or the protein phosphatase inhibitor sodium orthovanadate inhibitedDNA synthesis and they did not affect the genistein-mediated inhibition.
Finally, when the growing 3' end of one Okazaki fragment reaches the 5' end of the previous fragment, the resulting nick is sealed by the enzyme DNA ligase.
dns unscheduled DNA synthesis dom domestic animal (goat, ..
Unscheduled DNA Synthesis Test - MediLexicon
DNA polymerase δ was formerly thought to be the main replication enzyme, while α is involved with primase.
unscheduled DNA synthesis assay > test della sintesi …
However, DNA polymerase α also has DNA polymerase activity and extends the RNA primer by adding DNA nucleotides.
It works by decreasing the production of the virus's DNA
(DNA polymerase α does not have the 3' to 5' exonuclease activity needed for proofreading.)
neuorological abnormalities, unscheduled DNA synthesis; ..
The present AOP describes alkylating DNA damage to differentiating spermatogonia and spermatogonial stem cells. These spermatogenic cells types are diploid and DNA-repair proficient. Mutations arising in mitotically replicating spermatogonial stem cells are of the most concern, as these can persist and accumulate in the adult male. For example, as described above, recent evidence indicates that the average human male accumulates and passes on two new mutations for every year of his reproductive life (Kong et al. 2012).
substructure so that translocation of the polymerase down the DNA …
In chronic low-dose experiments with dogs (75 mGy/d for the duration of life), vital hematopoietic progenitors showed increased radioresistance along with renewed proliferative capacity (Seed and Kaspar 1992). Under the same conditions, a subset of animals showed an increased repair capacity as judged by the unscheduled DNA synthesis assay (Seed and Meyers 1993). Although one might interpret these observations as an adaptive effect at the cellular level, the exposed animal population experienced a high incidence of myeloid leukemia and related myeloproliferative disorders. The authors concluded that “the acquisition of radioresistance and associated repair functions under the strong selective and mutagenic pressure of chronic radiation is tied temporally and causally to leukemogenic transformation by the radiation exposure” (Seed and Kaspar 1992).
(DNA) and ribonucleic acid (RNA)
coli, DNA polymerase I (which has both 5' ---> 3' and 3' ---> 5' exonuclease activity in addition to its polymerase activity) removes the RNA primer and simultaneously synthesizes new DNA to replace it.
OECD Guidelines for the Testing of Chemicals - Wikipedia
Together with various data reported in theliterature, these patterns of a cell type-specific decrease of UDS and mtDNAsynthesis with age in the mouse brain lead to an improved understanding ofthe complex interrelationships between the molecular events associated withthe phenomenon of aging as well as to a new idea regarding the cause of thespecific distribution pattern of those cells in the human brain that areaffected by the formation of paired helical filaments in Alzheimer's disease.
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