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1.
Mitochondrial DNA evolution in the genus Equus 总被引:7,自引:0,他引:7
Employing mitochondrial DNA (mtDNA) restriction-endonuclease maps as the
basis of comparison, we have investigated the evolutionary affinities of
the seven species generally recognized as the genus Equus. Individual
species' cleavage maps contained an average of 60 cleavage sites for 16
enzymes, of which 29 were invariant for all species. Based on an average
divergence rate of 2%/Myr, the variation between species supports a
divergence of extant lineages from a common ancestor approximately 3.9 Myr
before the present. Comparisons of cleavage maps between Equus przewalskii
(Mongolian wild horse) and E. caballus (domestic horse) yielded estimates
of nucleotide sequence divergence ranging from 0.27% to 0.41%. This range
was due to intraspecific variation, which was noted only for E. caballus.
For pairwise comparisons within this family, estimates of sequence
divergence ranged from 0% (E. hemionus onager vs. E. h. kulan) to 7.8% (E.
przewalskii vs. E. h. onager). Trees constructed according to the parsimony
principle, on the basis of 31 phylogenetically informative restriction
sites, indicate that the three extant zebra species represent a
monophyletic group with E. grevyi and E. burchelli antiquorum diverging
most recently. The phylogenetic relationships of E. africanus and E.
hemionus remain enigmatic on the basis of the mtDNA analysis, although a
recent divergence is unsupported.
相似文献
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The consequence of harvesting young leaves of cassava as vegetable on the vulnerability of the crop to cassava mosaic disease (CMD) and on storage root yield was investigated using 30 cassava genotypes planted in IITA fields located in the humid forest (Port Harcourt?:?Onne), forest-savannah transition (Ibadan), southern guinea savannah (Mokwa) and northern guinea savannah (Zaria) agroecologies in Nigeria. Tender apical leaves and shoots of the cassava genotypes were removed from forty plants per cassava genotype with the same number of plants considered as control. Whitefly infestation, disease incidence (DI) and symptom severity (ISS) of the disease were assessed at monthly interval for six months and also at the ninth month after planting (MAP). Yield reduction due to this treatment was calculated as percentage harvest index (HI). Whitefly population fluctuated throughout the period of observation at all locations with higher population obtained generally for treated plants compared to control plants. Sprouting leaves of some treated genotypes were observed with severe mosaic symptoms, while corresponding control showed no mosaic symptoms. Contrarily, no remarkable difference was observed in Zaria between the mean ISS of treated and control cassava genotypes. There was a highly significant difference (P?<?0.01) in DI and ISS among cassava genotypes across all locations. Also, there was a highly significant interaction (P?<?0.01) in symptom severity between location (loc) and genotype, genotype and treatment (trt), loc and trt. Interaction between loc, genotypes and trt with regard to DI was highly significant at 2, 3 and 4 MAP, while with ISS, the interaction was highly significant all through the counting period. There was a positive relationship between DI and ISS on plants of genotypes 96/1039 and ISU. The percentage HI (27.4) of treated plants of genotype 95/0166 in Ibadan was remarkably lower than the value obtained for corresponding control (41.9) plants. Also, sharp distinction in% HI of treated (39.5) and control (43.8) ISU was observed in Onne with their respective ISS values as 3.7 and 3.2. Therefore, harvesting tender apical leaves and shoots of cassava as vegetables should be discouraged as it increases the severity of CMD infection in the regenerating shoots of cassava with attendant storage root yield reduction. 相似文献
4.
O. A. Kovaleva A. K. Shchyolkina O. K. Mamaeva V. A. Ol’shevskaya A. V. Makarenkov A. S. Semeikin A. A. Shtil O. F. Borisova D. N. Kaluzhny 《Molecular Biology》2013,47(3):453-460
Porphyrins are a chemical class that is widely used in drug design. Cationic porphyrins may bind to DNA guanine quadruplexes. We report the parameters of the binding of 5,10,15,20-tetrakis(N-carboxymethyl-4-pyridinium) porphyrin (P1) and 5,10,15,20-tetrakis(N-etoxycarbonylmethyl-4-pyridinium) porphyrin (P2) to antiparallel telomeric G-quadruplex formed by d(TTAGGG)4 sequence (TelQ). The binding constants (K i ) and the number of binding sites (N j ) were determined from absorption isotherms generated from the absorption spectra of complexes of P1 and P2 with TelQ. Compound P1 demonstrated a high affinity to TelQ (K i = (40 ± 6) × 106 M?1, N 1 = 1; K 2 = (5.4 ± 0.4) × 106 M?1, N 2 = 2). In contrast, the binding constants of P2-TelQ complexes (K 1 = (3.1 ± 0.2) × 106 M?1, N 1 = 1; K 2 = (1.2 ± 0.2) × 106 M?1, N 2 = 2) were one order of magnitude smaller than the corresponding values for P2-TelQ complexes. Measurements of the quantum yield and fluorescence lifetime of the drug’s TelQ complexes revealed two types of binding sites for P1 and P2 on the quadruplex oligonucleotide. We concluded that strong complexes can result from the interaction of the porphyrins with TTA loops whereas the weaker complexes are formed with G-quartets. The altered TelQ conformation detected by the circular dichroism spectra of P1-TelQ complexes can be explained by the disruption of the G-quartet. We conclude that peripheral carboxy groups contribute to the high affinity of P1 for the antiparallel telomeric G-quadruplex. 相似文献
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V S Samsonova N V Khokhlev E A Mamaeva N A Bakulina E N Sulimov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1977,(5):58-62
Fractions responsible for the main part of the serological and immunogenic activity differing by the set of antigens were isolated from the salt extracts of parapertussis microbes by gel-filtration on Sephadex G-100, ion exchange chromatography on DEAE-cellulose, and preparative electrophoresis in agar. Fractions, disclosing a sufficiently high serological activity and possessing the immunological properties, but containing the minimal set (2--3 out of 7) antigens, which were included in the initial extract, were isolated in the agar gel in the use of the preparative electrophoresis method. 相似文献
9.
Four-stranded DNA helices: conformational analysis of regular poly(dT).poly(dA).poly(dA).poly(dT) helices with various types of base binding 总被引:1,自引:0,他引:1
A A Chernyi I A Lysov YuPIl'ychova A S Zibrov A K Shchyolkina O F Borisova O K Mamaeva V L Florentiev 《Journal of biomolecular structure & dynamics》1990,8(3):513-527
The paper presents results obtained in conformational analysis of homopolymeric four-stranded poly(dT).poly(dA).poly(dA).poly(dT) DNA helices in which the pairs of strands with identical bases are parallel and have a two-fold symmetry axis. All possible models of base binding to yield a symmetric complex have been considered. The dihedral angles of sugar-phosphate backbones and helix parameters, which are consistent with the minima of conformational energy for four-stranded DNAs, have been determined using the results of optimization of conformational energy calculated at atom-atom approximation. Potential energy is shown to depend on the structure of base complexes and on the mutual orientation of unlike strands. Possible biological functions of four-stranded helices are discussed. 相似文献
10.
V S Samsonova N V Kholchev E A Mamaeva N A Bakulina E N Sulimov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1979,(10):76-80
Soluble parapertusis antigen, serologically active, having hemosensitive properties and containing only 2 antigenic components was obtained by the method of ethanol fractionation of microbial extracts. This method is simple and convenient for production purposes. The antigen thus obtained was used for the production of a highly specific erythrocytic diagnostic preparation (formalinized, liquid). When tested in reaction with animal and human sera, the new diagnostic preparation proved to be sufficiently active and species specific. 相似文献