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41.
Recently, a group of diplomonads has been found to use a genetic code in
which TAA and TAG encode glutamine rather than termination. To survey the
distribution of this characteristic in diplomonads, we sought to identify
TAA and TAG codons at positions where glutamine is expected in genes for
alpha-tubulin, elongation factor-1 alpha, and the gamma subunit of
eukaryotic translation initiation factor-2. These sequences show that the
variant genetic code is utilized by almost all diplomonads, with the genus
Giardia alone using the universal genetic code. Comparative phylogenetic
analysis reveals that the switch to this genetic code took place very early
in the evolution of diplomonads and was likely a single event. Termination
signals and downstream untranslated regions were also cloned from three
Hexamita genes. In all three of these genes, the predicted TGA termination
codon was found at the expected position. Interestingly, the untranslated
regions of these genes are high in AT. This is incongruent with the coding
regions, which are comparatively GC-rich.
相似文献
42.
N Lübcker J Dabrowski TA Zengeya PJ Oberholster G Hall S Woodborne 《African Journal of Aquatic Science》2016,41(4):399-411
The alien invasive silver carp Hypophthalmichthys molitrix established a self-sustaining feral population in an oligotrophic impoundment, Flag Boshielo Dam, in South Africa. The ability of this population to persist in a dam with low algal biomass (median annual suspended chlorophyll a = 0.08 µg l?1), and limited access to rivers considered large enough for successful spawning, has implications for their invasive potential in other systems. Stomach content and stable isotope analysis were used to assess the trophic ecology of H. molitrix, which was then compared with indigenous Mozambique tilapia Oreochromis mossambicus, on a seasonal basis during 2011. Hypophthalmichthys molitrix are generalist filter feeders, with a diet consisting primarily of sediment, vegetative detritus, dinoflagellates and diatoms. The dominance of sediments in their stomachs suggests occasional benthic scavenging. However, H. molitrix occupied a higher trophic level (TL = 2.8) than expected, suggesting that this population subsidised their diet with an unidentified dietary constituent, characterised by enriched nitrogen values. Although the stomach contents indicated dietary overlap between H. molitrix and O. mossambicus, stable isotopes revealed fine-scale resource partitioning, despite both species occupying the same trophic level. Nonetheless, the persistence of this feral H. molitrix population in an oligotrophic impoundment highlights their phenotypic plasticity. 相似文献
43.
PJ Gokhale 《Biotechnic & histochemistry》2016,91(8):540-548
The extraction of statistically meaningful quantitative information from microscopy images is increasingly important for modern biological research. Obtaining accurate, quantitative information from biological specimens, however, is a complex process that requires optimization of several parameters. One must consider the number of probes, fluorescent channels required, type of plate to be used, number of fields to be acquired and optimal resolution for image acquisition. The extraction of information from images is dependent on and can be aided greatly by careful consideration of the factors involved in the image acquisition process. I summarize here the general principles behind the imaging and software technology that is used to quantify images and highlight particular issues of concern for critically applying image quantitation techniques for research. 相似文献
44.
45.
W. R. Whalley I. C. Dodd C. W. Watts C. P. Webster A. L. Phillips J. Andralojc R. P. White W. J. Davies M. A. J. Parry 《Plant and Soil》2013,364(1-2):171-179
Background and aims
The role of the root system in mediating crop yields has recently been emphasised, resulting in several laboratory approaches for phenotyping root traits. We aimed to determine the existence of, and reasons for, genotypic variation in wheat (Triticum aestivum L.) root penetration of strong wax layers.Methods
Three contrasting groups (UK elite lines, CIMMYT lines and near-isogenic lines of cv Mercia containing dwarfing and semi-dwarfing Rht alleles) comprising 18 different genotypes with contrasting phenologies were studied. We determined the ability of roots of these genotypes to penetrate strong wax layers and the angular spread of the root systems.Results
There were no intrinsic differences in root system ability to penetrate strong wax layers (consistent with the similar root diameter of all lines) since greater root penetration was simply related to more root axes. Recording root penetration of concentric zones of the wax layer demonstrated that cv. Battalion had a root system with a smaller angular spread than cv. Robigus, which had the root system with the greatest angular spread.Conclusions
There was limited genotypic variability in root penetration of strong layers within the wheat cultivars studied. A key challenge will be to determine the physiological and agronomic significance of the variation in root angular spread. 相似文献46.
Surveys were distributed to New Zealand land users in 1998 and 2008 to acquire information about New Zealand frogs with the aim of compiling and mapping their distribution and inferred population trends without costly and time-consuming field surveys. The overall frog population trend was reported as declining, with possible causes reported as an increase in agriculture, an increase in the distribution of predatory fish and disease. The resultant maps could be used for four main purposes: 1) to identify regions where Litoria populations are known to occur, which can be eliminated when considering suitable regions for translocation of Leiopelma; 2) to identify growing or stable populations of Litoria species, which may assist future disease surveys, population monitoring and to identify sources of genetic material that may serve as an Ark for declining Australian populations; 3) to highlight populations that are in decline to enable effective targeting of detailed disease studies; and 4) to approximate the stability of amphibian populations in the absence of more accurate, but costly, scientific monitoring. 相似文献
47.
48.
Emma L Hesketh John RP Knight Rosemary HC Wilson James PJ Chong Dawn Coverley 《Cell cycle (Georgetown, Tex.)》2015,14(3):333-341
The minichromosome maintenance complex (MCM2-7) is the putative DNA helicase in
eukaryotes, and essential for DNA replication. By applying serial extractions to mammalian
cells synchronized by release from quiescence, we reveal dynamic changes to the
sub-nuclear compartmentalization of MCM2 as cells pass through late G1 and early S phase,
identifying a brief window when MCM2 becomes transiently attached to the nuclear-matrix.
The data distinguish 3 states that correspond to loose association with chromatin prior to
DNA replication, transient highly stable binding to the nuclear-matrix coincident with
initiation, and a post-initiation phase when MCM2 remains tightly associated with
chromatin but not the nuclear-matrix. The data suggests that functional MCM complex
loading takes place at the nuclear-matrix. 相似文献
49.
Apoptosis is characterized by DNA strand breaks with a 3'-OH terminus, which are analyzed by terminal deoxy(d)-UTP nick end labeling (TUNEL). Proteinase K digestion is thought to be an essential step in the TUNEL procedure. The effects of decalcifying reagents on general staining and the TUNEL assay for cartilage sections are largely unknown. The effects of these reagents on retention and integrity of DNA in chondrocytes have not been described until now. We evaluated the effects of various decalcifying solutions, including 10% EDTA, 10% citric acid, 5% trichloroacetic acid, 5% acetic acid and a commercial hydrochloric acid-based reagent, on general cartilage staining and the TUNEL assay for cartilage. The effects of proteinase K on nucleus preservation were also examined. Decalcification with 10% EDTA gave the best result for general cartilage staining. Chondrocyte DNA was retained and intact after using this reagent. Decalcification with 10% EDTA is also the safest method of decalcification if the TUNEL assay is applied to cartilage. Proteinase K digestion may have adverse effects on nucleus preservation in cartilage. Awareness of these effects is important whenever the TUNEL assay is applied. 相似文献
50.
MG Mullender NA Blom M De Kleuver JM Fock WMGC Hitters AMC Horemans CJ Kalkman JEH Pruijs RR Timmer PJ Titarsolej NC Van Haasteren Tol-de MJ Van Jager AJ Van Vught BJ Van Royen 《Scoliosis》2008,3(1):1-14