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Genomic mutation in lines of Arabidopsis thaliana exposed to ultraviolet-B radiation.
Studies that have attempted to estimate the rate of deleterious mutation have typically been conducted under low levels of ultraviolet-B (UV-B) radiation, a naturally occurring mutagen. We conducted experiments to test whether the inclusion of natural levels of UV-B radiation in mutation-accumulation (MA) experiments influences the rate and effects of mildly deleterious mutation in the plant Arabidopsis thaliana. Ten generations of MA proved insufficient to observe significant changes in means or among-line variances in experimental lines maintained either with or without supplemental UV-B radiation. Maximum-likelihood estimates of mutation rate for total flower number revealed a small but significant rate of mutation for MA lines propagated under supplemental UV-B exposure, but not for those in which supplemental UV-B was omitted. A fraction of the flower number mutations under UV-B (approximately 25-30%) are estimated to increase flower number. Results from the application of transposon display to plant materials obtained after MA, in both the presence and absence of supplemental UV-B, suggest that the average rate of transposition for the class I and II transposable elements (TEs) surveyed was no more than 10(-4). Overall, the estimates of mutation parameters are qualitatively similar to what has been observed in other MA experiments with this species in which supplemental UV-B levels have not been used. As well, it appears that naturally occurring levels of UV-B do not lead to detectable increases in levels of transposable element activity.
[The comparison of sensitivity between immunostaining and a simplified PCR-cold SSCP method in p53 genomic mutations].
The PCR-SSCP (single strand conformational polymorphism) method has been widely employed to screen mutations in a variety of genes because of its rapidity and simplicity in the operation. Using this method, we have examined mutations of some tumor-related genes including p53 and Ki-ras. In this study, we have evaluated the PCR-Cold (non radioactive) SSCP method for detection of p53 point mutations in comparison with immunohistological detection of p53 and PCR-direct sequencing. The results indicated that the PCR-Cold SSCP method had the same sensitivity with that of PCR-direct sequencing method, and had higher sensitivity than that of immunohistochemical method (IHC).
[Clinical and genetic consequences of ring chromosome, a structural genome mutation].
Ring chromosome is a peculiar genetic anomaly which may cause phenotypic abnormalities even without a loss of genetic material. The ring formation of chromosome ends induces difficulties in the sister chromatid separation at cell division, resulting in increased cell death rate through the generation of secondary aneuploid cells. Based on the in vitro analyses of own cases and a review of more than 200 case reports published in the literature, the author presents some conclusions on "ring syndrome", a non-specific clinical manifestation of ring formation of any chromosome, consisting of the lack of (or poorly expressed) organic manifestations, mild or borderline mental retardation, and a severe growth failure which is not explained by organic, biochemical, or endocrine findings. It is also suggested that the phenotypic manifestation of a ring chromosome is even less expressed when the ring is transmitted to the next generation. Based on observations of ring behaviour and the clinical phenotypes in a 3-generational family with a mosaic supernumerary ring, it is not unrealistic to assume that there is a transgenerational increase in the severity of the clinical manifestation resulting from a less efficient elimination process against the ring (cytogenetic anticipation).
[An attempt to identify the most frequent genomic mutations responsible for isolated deafness in patients after cochlear implantation].
The aim of this study was to identify subjects with 35delG mutation of GJB2 gene as the most frequent genetic cause of deafness. Deaf patients receiving cochlear implantation at the ENT Clinic at University of Medical Sciences in Poznań and their family members were recruited to the study. Peripheral blood lymphocytes DNA was amplified in allele-specific PCR and analysed for single strand conformation polymorphism (SSCP) to detect mutation at DFNB1 locus. 35delG mutation at both alleles was found at 42.9% of deaf patients and 29.4% of health relatives were found to be carrier of the mutation at one allele. The study is thought to be a first step in analysis of typical mutations in Polish deaf population.
On the mechanisms of induced aneuploidy in Aspergillus nidulans and validation of tests for genomic mutations.
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[Chromosome and genome mutation in newborn infants].
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[Variation and selection in clone populations of murine rhabdomyosarcoma in vivo. I. Frequency of genomic mutations].
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[Varibaility and selection in clonal populations of HeLa cells. 3. Frequency of genomic mutations].
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[Frequency of genomic mutations of tumor cells while cloning in vivo].
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[Animal experiment studies of radiation-induced genome mutations in bone marrow cells].
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[Frequency of lethal chromosomal and genome mutations in man].
According to the cytogenetic studies chromosome anomalies frequency in 209 children who died in the perinatal period was 7.2 per cent. These cases were found to consist of 8 autosome trisomies, 5 anomalies in sex chromosome system, 1 case of triploidy and 1 case of structural reorganization. Accounting for the elimination of chromosome anomalies during the early periods of fetus development, the frequency of chromosome lethals was shown to be 6.44 X 10(-2) in registered pregnancies and 54.89 X 10-2 in conceptions.
[Genome mutation yield in the cells of intact and regenerating liver of normal rats and following gamma irradiation].
A comparative study was made of spontaneous and induced polyploidy in cells of resting and regenerating rat liver. Polyploidy was shown to play a major role in the ontogenesis and during regeneration after partial hepatectomy. An essential difference was revealed in the radiation response of cells of intact and regenerating liver with respect to the yield of polyploid cells. This distinction was referred to different effectiveness of the processes of repair and fixation of radiation damages in the actively proliferating and resting cells.
[Effect of short-wave UV irradiation on the genome mutation frequency in HeLa cell clone populations].
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[Detection and prevalence of mitochondrial genome mutations in diabetes].
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Usefulness of Mycobacterium tuberculosis genomic mutations in the genes katG and inhA for the prediction of isoniazid resistance.
SETTING: Mutations in two genes of Mycobacterium tuberculosis, inhA and katG, are known to correlate with resistance to isoniazid (INH). OBJECTIVE: To determine which mutation or mutations are the most predictive for INH resistance and the most frequent ones in such isolates. Further, to propose a simple and generally applicable method for their detection. DESIGN: Codons 94 and 95 in the inhA gene and codons 315 and 463 in the katG gene were characterized in 50 INH-resistant and 12 INH-sensitive isolates from Germany and Sierra Leone. RESULTS: Mutations in codon 315 of the katG gene were detected in 27 of the INH-resistant and none of the INH-sensitive isolates. All mutations in this codon altered an AciI restriction enzyme site. No mutations were found in the investigated codons of the inhA gene. CONCLUSION: We propose that most INH resistances can be rapidly predicted by a simple AciI restriction enzyme digest of a polymerase chain reaction (PCR)-amplified katG fragment.
Evolution: constantly avoiding mutation.
The genomic mutation rate of the archaeon Sulfolobus acidocaldarius, which inhabits a harsh and potentially mutagenic environment, surprisingly agrees well with the previously observed constancy of genomic mutation rates in microbes. The evolutionary explanation for this constancy of genomic mutation rates remains obscure.
Identification of genes that protect the C. elegans genome against mutations by genome-wide RNAi.
An RNA interference (RNAi)-based genome-wide screen was performed to detect genes that contribute to genome stability in somatic cells of Caenorhabditis elegans. We identified 61 such genes; these also affect spontaneous mutagenesis in the germ line. Their sequence suggests a role in DNA repair and/or replication, in chromatin remodeling, or in cell cycle control; there are also many novel genes that are highly conserved from yeast to human. Because known mutator genes are causally involved in many hereditary and sporadic human cancers, it is likely that some of these new mutators are equally relevant in cancer etiology.