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291.
293.
Mitochondrial DNA variation and genetic structure in populations of Drosophila melanogaster 总被引:5,自引:0,他引:5
The understanding of the genetic structure of a species can be improved by
considering together data from different types of genetic markers. In the
past, a number of worldwide populations of Drosophila melanogaster have
been extensively studied for several such markers, including allozymes,
chromosomal inversions, and quantitative characters. Here we present
results from a study of restriction- fragment-length polymorphisms of
mitochondrial DNA (mtDNA) in 92 isofemale lines from many of the same
geographic populations of D. melanogaster. Eleven restriction enzymes were
used, of which four revealed restriction-site polymorphism. A total of 24
different haplotypes were observed, of which 18 were unique to single
populations. In many populations, the unique haplotypes have reached high
frequency without being observed in neighboring populations. A Wagner
parsimony tree reveals that mutationally close variants show geographical
clumping, suggesting local differentiation of mtDNA in populations. The
Old-World and the New-World populations are differentiated, with the
predominant Old-World haplotype being virtually absent from the New World.
These results contrast with those for the nuclear genes, in which many loci
show parallel clines in different continents, and suggest a common origin
of D. melanogaster populations in North America.
相似文献
294.
295.
296.
Field Trials of Fish Marking using a Jet Inoculator 总被引:1,自引:0,他引:1
297.
298.
Analysis of the in vivo phosphorylation state of rabbit skeletal muscle glycogen synthase by fast-atom-bombardment mass spectrometry 总被引:5,自引:0,他引:5
L Poulter S G Ang B W Gibson D H Williams C F Holmes F B Caudwell J Pitcher P Cohen 《European journal of biochemistry》1988,175(3):497-510
The in vivo phosphorylation state of glycogen synthase was re-examined by fast-atom-bombardment mass spectrometry and a procedure in which phosphoserine residues are first converted to S-ethylcysteine. In animals injected with the beta-adrenergic antagonist propranolol, the phosphorylation sites in the N-terminal (N) and C-terminal (C) cyanogen bromide peptides were identified as the serine residues at N7, the region C28-C39, C42, C46 and C100. In animals injected with adrenalin, the phosphorylation of N7 increased from 0.6 to 0.8 mol/mol, the region C28-C39 from 0.7 to 1.2 mol/mol and C100 from 0.3 to 0.6 mol/mol. The phosphorylation states of C42 (0.7 mol/mol) and C46 (0.9 mol/mol) were unchanged. In addition, two further serine residues became phosphorylated at positions N10 (0.5 mol/mol) and C87 (0.5 mol/mol), which were not phosphorylated in the absence of adrenalin. Residues N10 and C42 have not been recognized as in vivo sites of phosphorylation previously. The results suggest that N10 is phosphorylated by a novel protein kinase which may be activated by cyclic-AMP-dependent protein kinase. The phosphorylation of C42 is likely to be catalysed by glycogen synthase kinase 3. The protein kinases responsible for phosphorylating N7, the region C28-C39, C46, C87 and C100 in vivo and the molecular mechanisms by which adrenalin inactivates glycogen synthase in vivo are discussed. Residue N3, a major site phosphorylated by casein kinase-I in vitro is not phosphorylated in vivo. This and other evidence indicates that casein kinase-I is not a glycogen synthase kinase in vivo. 相似文献
299.
Glycogenin is the priming glucosyltransferase required for the initiation of glycogen biogenesis in rabbit skeletal muscle 总被引:7,自引:0,他引:7
Purified preparations of glycogen synthase are a complex of two proteins, the catalytic subunit of glycogen synthase and glycogenin, present in a 1:1 molar ratio [J. Pitcher, C. Smythe, D. G. Campbell & P. Cohen (1987) Eur. J. Biochem. 169, 497-502]. This complex has now been found to contain a further glucosyltransferase activity that catalyses the transfer of glucose residues from UDP-Glc to glucosylated-glycogenin. The glucosyltransferase, which is of critical importance in forming the primer required for de novo glycogen biosynthesis, is distinct from glycogen synthase in several ways. It has an absolute requirement for divalent cations, a 1000-fold lower Km for UDP-Glc and its activity is unaffected by incubation with UDP-pyridoxal or exposure to 2 M LiBr, which inactivate glycogen synthase by 95% and 100%, respectively. The priming glucosyltransferase and glycogen synthase activities coelute on Superose 6, and the rate of glycosylation of glycogenin is independent of enzyme concentration, suggesting that the reaction is catalysed intramolecularly by a subunit of the glycogen synthase complex. This component has been identified as glycogenin, following dissociation of the subunits in 2 M LiBr and their separation on Superose 12. The glycosylation of isolated glycogenin reaches a plateau when five additional glucose residues have been added to the protein, and digestion with alpha-amylase indicates that all the glycogenin molecules contain at least one glucosyl residue prior to autoglucosylation. The priming glucosyltransferase activity of glycogenin is unaffected by either glucose 6-phosphate or by phosphorylation of the catalytic subunit of glycogen synthase. The mechanism of primer formation is discussed in the light of the finding that glycogenin is an enzyme that catalyses its own autoglucosylation. 相似文献
300.
Shoals composed of equal numbers of two size-classes of European minnows were observed undisturbed, feeding and after threat from a pike in a large arena tank.
The time/frequency budget and analysed sequences of behaviour of the two size-classes were very similar. Irrespective of size, for standard behaviour measures, fish in the shoal behaved similarly under the same external influences, including predator threat.
In contrast, however, the distribution of the two size-classes provided evidence of size segregation within the shoal. This was brought about by individual minnows making shoaling responses preferentially to their own size-class. After exposure to the predator, shoaling responses changed and differed between small and large minnows.
The outcomes of contests at foraging patches were governed primarily by fish size and information asymmetry rather than by occupation of a feeding site.
The experiment shows that asymmetrical pay-offs in foraging and in response to predator threat are the probable reasons for size-segregation behaviours. This conclusion supports the views of earlier workers that mechanical sorting by swimming speed is not an important factor in size segregation in shoals. 相似文献
The time/frequency budget and analysed sequences of behaviour of the two size-classes were very similar. Irrespective of size, for standard behaviour measures, fish in the shoal behaved similarly under the same external influences, including predator threat.
In contrast, however, the distribution of the two size-classes provided evidence of size segregation within the shoal. This was brought about by individual minnows making shoaling responses preferentially to their own size-class. After exposure to the predator, shoaling responses changed and differed between small and large minnows.
The outcomes of contests at foraging patches were governed primarily by fish size and information asymmetry rather than by occupation of a feeding site.
The experiment shows that asymmetrical pay-offs in foraging and in response to predator threat are the probable reasons for size-segregation behaviours. This conclusion supports the views of earlier workers that mechanical sorting by swimming speed is not an important factor in size segregation in shoals. 相似文献