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71.
The mutation rates of di-, tri- and tetranucleotide repeats in Drosophila melanogaster 总被引:4,自引:1,他引:3
Schug MD; Hutter CM; Wetterstrand KA; Gaudette MS; Mackay TF; Aquadro CF 《Molecular biology and evolution》1998,15(12):1751-1760
In a recent study, we reported that the combined average mutation rate of
10 di-, 6 tri-, and 8 tetranucleotide repeats in Drosophila melanogaster
was 6.3 x 10(-6) mutations per locus per generation, a rate substantially
below that of microsatellite repeat units in mammals studied to date (range
= 10(-2)-10(-5) per locus per generation). To obtain a more precise
estimate of mutation rate for dinucleotide repeat motifs alone, we assayed
39 new dinucleotide repeat microsatellite loci in the mutation accumulation
lines from our earlier study. Our estimate of mutation rate for a total of
49 dinucleotide repeats is 9.3 x 10(-6) per locus per generation, only
slightly higher than the estimate from our earlier study. We also estimated
the relative difference in microsatellite mutation rate among di-, tri-,
and tetranucleotide repeats in the genome of D. melanogaster using a method
based on population variation, and we found that tri- and tetranucleotide
repeats mutate at rates 6.4 and 8.4 times slower than that of dinucleotide
repeats, respectively. The slower mutation rates of tri- and
tetranucleotide repeats appear to be associated with a relatively short
repeat unit length of these repeat motifs in the genome of D. melanogaster.
A positive correlation between repeat unit length and allelic variation
suggests that mutation rate increases as the repeat unit lengths of
microsatellites increase.
相似文献
72.
拐芹根化学成分研究Ⅱ 总被引:3,自引:0,他引:3
从伞型科当归属植物拐芹(Angelica polymorpha Maxim)的根及根茎中又分得4个结晶性化合物。经物理常数测定、光谱分析,分别鉴定为欧前胡素Ⅰ,异氧化前胡内酯Ⅱ,Pabulenol Ⅲ,Phellopterin Ⅳ。 相似文献
73.
The redox properties, absorption, electroabsorption, CD, EPR, and P+QA- recombination kinetics have been measured for the special pairs of two mutants of Rhodobacter capsulatus reaction centers involving amino acid changes in the vicinity of the special pair, P. Both mutants symmetrize amino acid residues so that portions of the M-sequence are replaced with L-sequence: sym1 symmetrizes all residues between M187 and M203, whereas (M)F195H is a single amino acid subset of the sym1 mutation. (M)F195H introduces a His residue in a position where it is likely to form a hydrogen bond to the acetyl group of the M-side bacteriochlorophyll of P. For both mutants compared with wild-type, (i) the redox potential is at least 100 meV greater, (ii) the P+QA- recombination rate is about twice as fast at room temperature, and (iii) the large electroabsorption feature for the QY band of P is shifted relative to the absorption spectrum. The comparison of the properties observed for the sym1 and (M)F195H reaction center mutants and the differences between these mutants and wild-type suggest that residue M195 is an important determinant of the properties of the special pair. 相似文献
74.
Mitochondrial DNA (mtDNA) sequences that include (a) a part of the
cytochrome b gene, (b) two tRNA genes, and (c) a part of the noncoding
D-loop region of 31 Anguilla japonica (Japanese eel) and 1 A. marmorata
collected from Taiwan, Japan, and mainland China were determined to
evaluate the population structure of Japanese eel. Among 30 genotypes
identified from the 31 Japanese eel mtDNAs sequenced, there are 58 variable
sites, predominantly clustered at the D-loop region. The phylogenetic tree
constructed by the unweighted pair-group method with arithmetic mean shows
neither significant genealogical branches nor geographic clusters.
Furthermore, the sequence-statistics test reveals little, if any,
significant genetic differentiation. These results indicate that the 31
Japanese eels might come from a single population. Analysis of sequence
variation in mtDNA by using the relationship between the number of
segregating sites and the average number of nucleotide differences under
the neutral mutation hypothesis reveals that neutral mutation acts as a
major factor influencing the evolutionary divergence of the Japanese eel
mitochondrial genome sequenced, especially in the noncoding region.
相似文献
75.
Muehlenbein MP Campbell BC Phillippi KM Murchison MA Richards RJ Svec F Myers L 《Journal of medical primatology》2001,30(5):273-282
Though baboons have been considered an appropriate non-human primate model for studying human reproductive and endocrine development. the overall similarity of reproductive maturation between the two species is unclear. This paper examines the role of testicular and adrenal hormones for pubertal changes in a cross-sectional sample of 21 captive male savanna baboons. Morphometric and hormonal indices demonstrate changes in size and gonadal function, but not adrenal function, during pubertal maturation among baboons. Results also indicate that gonadal, but not adrenal, androgens are related to morphometric variables. We conclude that savanna baboons do not make an appropriate evolutionary model of human pubertal maturation. 相似文献
76.
用图像分析系统和通道阻断法研究了原代人胎儿鼻咽上皮细胞的调节性容积回缩(regulatoryvolumedecrease,RVD)能力及其机制。结果发现,低渗刺激可诱发鼻咽上皮细胞产生RVD,在160-240mOsmol/L范围内,RVD强弱与渗透压呈“S”形负相关(r=-0.99,P<0.05),与细胞肿胀程度呈“S”形正相关(=0.99,P<0.05)。Cl~-通道阻断剂tamoxifen(20μmol/L),ATP(10mmol/L)或NPPB(100μmol/L)对RVD阻抑率分别为100%(P<0.01),76.3%(P<0.01)和62.7%(P<0.01)。本研究表明,鼻咽上皮细胞受到低渗刺激时可产生RVD,Cl~-通道开放是其RVD的关键机制。 相似文献
77.
Mateus F Santana José CF Silva Eduardo SG Mizubuti Elza F Araújo Bradford J Condon B Gillian Turgeon Marisa V Queiroz 《BMC genomics》2014,15(1)
Background
Cochliobolus heterostrophus is a dothideomycete that causes Southern Corn Leaf Blight disease. There are two races, race O and race T that differ by the absence (race O) and presence (race T) of ~ 1.2-Mb of DNA encoding genes responsible for the production of T-toxin, which makes race T much more virulent than race O. The presence of repetitive elements in fungal genomes is considered to be an important source of genetic variability between different species.Results
A detailed analysis of class I and II TEs identified in the near complete genome sequence of race O was performed. In total in race O, 12 new families of transposons were identified. In silico evidence of recent activity was found for many of the transposons and analyses of expressed sequence tags (ESTs) demonstrated that these elements were actively transcribed. Various potentially active TEs were found near coding regions and may modify the expression and structure of these genes by acting as ectopic recombination sites. Transposons were found on scaffolds carrying polyketide synthase encoding genes, responsible for production of T-toxin in race T. Strong evidence of ectopic recombination was found, demonstrating that TEs can play an important role in the modulation of genome architecture of this species. The Repeat Induced Point mutation (RIP) silencing mechanism was shown to have high specificity in C. heterostrophus, acting only on transposons near coding regions.Conclusions
New families of transposons were identified. In C. heterostrophus, the RIP silencing mechanism is efficient and selective. The co-localization of effector genes and TEs, therefore, exposes those genes to high rates of point mutations. This may accelerate the rate of evolution of these genes, providing a potential advantage for the host. Additionally, it was shown that ectopic recombination promoted by TEs appears to be the major event in the genome reorganization of this species and that a large number of elements are still potentially active. So, this study provides information about the potential impact of TEs on the evolution of C. heterostrophus.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-536) contains supplementary material, which is available to authorized users. 相似文献78.
Mattia CF Prosperi Susana Marinho Angela Simpson Adnan Custovic Iain E Buchan 《BMC medical genomics》2014,7(Z1):S7
Background
There is increasing recognition that asthma and eczema are heterogeneous diseases. We investigated the predictive ability of a spectrum of machine learning methods to disambiguate clinical sub-groups of asthma, wheeze and eczema, using a large heterogeneous set of attributes in an unselected population. The aim was to identify to what extent such heterogeneous information can be combined to reveal specific clinical manifestations.Methods
The study population comprised a cross-sectional sample of adults, and included representatives of the general population enriched by subjects with asthma. Linear and non-linear machine learning methods, from logistic regression to random forests, were fit on a large attribute set including demographic, clinical and laboratory features, genetic profiles and environmental exposures. Outcome of interest were asthma, wheeze and eczema encoded by different operational definitions. Model validation was performed via bootstrapping.Results
The study population included 554 adults, 42% male, 38% previous or current smokers. Proportion of asthma, wheeze, and eczema diagnoses was 16.7%, 12.3%, and 21.7%, respectively. Models were fit on 223 non-genetic variables plus 215 single nucleotide polymorphisms. In general, non-linear models achieved higher sensitivity and specificity than other methods, especially for asthma and wheeze, less for eczema, with areas under receiver operating characteristic curve of 84%, 76% and 64%, respectively. Our findings confirm that allergen sensitisation and lung function characterise asthma better in combination than separately. The predictive ability of genetic markers alone is limited. For eczema, new predictors such as bio-impedance were discovered.Conclusions
More usefully-complex modelling is the key to a better understanding of disease mechanisms and personalised healthcare: further advances are likely with the incorporation of more factors/attributes and longitudinal measures.79.
Persea americana agglutinin (PAA), a substance known to bind basic proteins and inhibit the sucrose-independent adherence of Streptococcus mutants to saliva = coated hydroxyapatite (Staat et al., 1980) was used to selectively enrich for mutants defective in a variety of cell surface associated virulence characteristics from cultures UAB62 (PS14 Riff, serotype c), UAB66 (6715 Strr Spcr, serotype g) and UAB77 (GS5, serotype c). Following mutagenesis and growth for segregation and phenotypic expression, washed cells of each strain were exposed to PAA overnight at 37 degrees C. Aggregated cells were removed by low-speed centrifugation and cells remaining in the supernatant fluids were concentrated, grown to stationary phase and the enrichment with PAA repeated. Mutants isolated following enrichment were phenotypically diverse and included strains defective in one or more of the following characteristics: adherence to glass in a sucrose-containing medium, aggregation with sucrose, dextran or PAA. dextranase production, colony morphology, cell or chain morphology, fermentation of sorbitol, lactose, galactose, raffinose, melibiose, or fructose, and production of surface protein antigen A (SpaA). The diversity of mutant phenotypes identified along with the observation that PAA could still cause aggregation (with a lower efficiency) of all mutants leads us to infer that the interaction of this agglutinin with proteins on the S. mutans cell surface is relatively nonspecific and that the observed inhibition of S. mutants attachment to saliva-coated hydroxyapatite caused by PAA is not due to a highly specific unique interaction of PAA with the protein(s) responsible for sucrose-independent adherence. 相似文献
80.