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1.
Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex 总被引:14,自引:1,他引:13
Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1-
kbp portion of the yolk protein 2 locus, were sequenced in six individuals
from each of four species: Drosophila melanogaster, D. simulans, D.
mauritiana, and D. sechellia. The species and strains were the same as
those of a previous study of a 1.9-kbp region of the period locus. No
evidence was found for recent balancing or directional selection or for the
accumulation of selected differences between species. Yolk protein 2 has a
high level of amino acid replacement variation and a low level of
synonymous variation, while zeste has the opposite pattern. This contrast
is consistent with information on gene function and patterns of codon bias.
Polymorphism levels are consistent with a ranking of effective population
sizes, from low to high, in the following order: D. sechellia, D.
melanogaster, D.mauritiana, and D. simulans. The apparent species
relationships are very similar to those suggested by the period locus
study. In particular, D. simulans appears to be a large population that is
still segregating variation that arose before the separation of D.
mauritiana and D. sechellia. It is estimated that the separation of
ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The
separations of D. sechellia and D. mauritiana from ancestral D. simulans
appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged
from ancestral D. simulans 0.1 Myr more recently than D. sechellia.
相似文献
2.
Preben D. Thomsen Hanne Qvist Lena Marklund Leif Andersson Hans Sjöström Ove Norén 《Mammalian genome》1993,4(10):604-607
A porcine 2-kb partial dipeptidylpeptidase IV (DPP4, EC 3.4.14.5) cDNA clone and a porcine 16-kb genomic fragment containing parts of the DPP4 gene were isolated, characterized, and used as probes to map the DPP4 gene to pig Chr (Chr) 15q21 by fluorescence in situ hybridization. A two-allele RFLP was revealed for the DPP4 gene. This polymorphism was utilized in a linkage test against the erythrocyte antigen G (EAG), previously assigned to Chr 15, and the microsatellite S0088, which is linked to EAG. The linkage analyses revealed significant evidence for linkage confirming the assignment of DPP4 to Chr 15. 相似文献
3.
Human aminopeptidase N is encoded by 20 exons 总被引:1,自引:0,他引:1
4.
5.
Size and shape of two intestinal dipeptidases 总被引:1,自引:0,他引:1
Physicochemical parameters were determined on glycyl-L-leucine hydrolase (glycy-leucine dipeptidase, EC 3.4.13.2) and aminoacyl-L-proline hydrolase (proline dipeptidase, EC 3.4.13.9), purified from pig small intestine. The native molecular weights were found to be 115,000 and 113,000, respectively, as determined by a sedimentation equilibrium technique. Under denaturing conditions the molecular weights were found to be 51,000 and 63,200, respectively, using the same technique. It is concluded that each dipeptidase is composed of two subunits of equal molecular weight. The two dipeptidases have the same Stokes radius, 4.2 nm, analysed by gel chromatography. The sedimentation coefficients were found to be 5.8. S and 6.5 S and the intrinsic viscosities 5.4 ml/g and 5.8 ml/g, respectively. For both dipeptidases the measured physicochemical parameters are in accordance with the model of a prolate ellipsoid of revolution, having an axial ratio of about 5. 相似文献
6.
Microvillus aminopeptidase (EC 3.4.11.2) is an enzyme with a molecular weight around 300 000. Normal preparations contain three different subunits (subunit A, Mr 162 000; subunit B, Mr 123 000; subunit C, Mr 61 000). The relationship between the three subunits was studied by immunoelectrophoresis using specific antibodies against individual denatured subunits and by densitometric scanning of polyacrylamide gels after separation of the three subunits. The results suggest that microvillus aminopeptidase initially appears in the membrane as a symmetric molecule built up to two identical A subunits. These subunits are then split into equimolar amounts of subunit B and subunit C by trypsin. Subunit B cannot generate subunit C but may be further degraded. The reaction sequence described is one which occurs in vivo. Treatment of purified aminopeptidase with trypsin increases the specific activity twofold. This phenomenon does not seem to be correlated to the generation of subunit B and subunit C or to the transformation of amphiphilic form into hydrophilic form. 相似文献
7.
In polarized epithelial cells aminopeptidase N is targeted to the apical membrane. The aim of this study was to determine whether a sorting signal is necessary for its correct transport to the apical membrane and, if so, to localize this sorting signal to one of the domains of the transmembrane protein. Anchor-minus aminopeptidase N, consisting of the hemagglutinin signal peptide including its cleavage site, and the ectoplasmic domain of human aminopeptidase N were stably expressed in Madin-Darby canine kidney cells cultured on polycarbonate filters. By measurement of the enzymatic activity it was found that the anchor-minus aminopeptidase N was secreted in a polarized manner to the apical side. As a reference the secretion of the secretory granule protein, cystatin C, was likewise studied. Cystatin C was found to be secreted in a nonpolarized manner to both domains. Our data thus show that human aminopeptidase N carries an apical sorting signal and that it is localized on the ectodomain of the enzyme. 相似文献
8.
Sulphur mineralization and adsorption in soils 总被引:2,自引:0,他引:2
Yahya M. Nor 《Plant and Soil》1981,60(3):451-459
Summary Studies were conducted to determine the comparative sulphur mineralizing capacity of selected Malaysian and Iowan soils and to determine the amounts of available and adsorbed sulphate in a number of Malaysian soils. Results of the mineralization study indicated that more sulphur mineralised from Malaysian soils although their average contents of total sulphur were lower compared to Iowan Soils. For both sets of soils, significant correlations between contents of organic carbon and total sulphur existed indicating that most of the sulphur was in organic combination. Phosphate solution consistently extracted higher quantities of sulphate in comparison to chloride solution in the Malaysian surface soils implying that a portion of the sulphate existed in adsorbed form. Adsorption of sulphate in soils was found to be dependent on concentration of sulphate added and followed the Langmuir adsorption isotherm. 相似文献
9.
Amirah Hurzaid Tin-Yam Chan Siti Azizah Mohd Nor Zainal Abidin Muchlisin Wei-Jen Chen 《Zoologica scripta》2020,49(5):596-613
The decapod family Penaeidae comprises most of the economically important marine shrimp species. Its members are widespread throughout the world, with its highest species diversity centred in the Indo-West Pacific region. Despite this importance, their taxonomy, classification and phylogeny are not yet settled due in part to incongruence among hypotheses proposed from molecular versus morphological studies. In this study, using a thorough taxonomic sampling of especially the South-East Asian species, we aim to (a) utilize a reconstructed phylogeny to test the monophyly of the Penaeidae and its currently recognized genera and (b) explore its species diversity in South-East Asian waters. To infer the phylogeny, a combined gene data set (including 109 ingroup and six outgroup taxa) of mitochondrial genes, COI and 16S rRNA, and two nuclear genes, NaK and PEPCK, was utilized. To explore its diversity, another data set that included 371 COI gene sequences (231 newly generated and 140 retrieved from public sources) was compiled and subsequently analysed with two different tools (ABGD and bPTP) for species delimitation. Other than supporting the non-monophyly of the Penaeidae with the Sicyoniidae nested within the penaeid tribe Trachypenaeini, the genera Penaeus, Mierspenaeopsis and Parapenaeopsis were also revealed to be polyphyletic. Our species delimitation analysis inferred that 94 putative species actually existed within the 71 morphospecies reviewed, indicating an underestimated biodiversity in this family and the potential presence of new species within the following morphospecies: Kishinouyepenaeopsis cornuta, K. incisa, Mierspenaeopsis sculptilis, M hardwicki, Parapenaeopsis coromandelica and Penaeus monodon. 相似文献
10.