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491.
Nucleotide sequence of the D-loop region of the sperm whale (Physeter macrocephalus) mitochondrial genome 总被引:4,自引:0,他引:4
We have amplified, by the polymerase chain reaction, and have sequenced the
D-loop region of the mitochondrial DNA from the sperm whale (Physeter
macrocephalus). The sperm whale D-loop was aligned with D- loop sequences
from four other cetaceans (Commerson's dolphin, orca, fin whale, and minke
whale) and an out-group (cow). This alignment showed the sperm whale
sequence to be larger than that of other cetaceans. In addition, some
sequence blocks were highly conserved among all six species, suggesting
roles in the functioning of mitochondrial DNA. Other blocks that were
previously reported to be well conserved among cetaceans showed little
sequence conservation with the sperm whale D-loop, which argues against the
functional importance of these sequence blocks in cetaceans.
相似文献
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Deuterostome phylogeny and the sister group of the chordates: evidence from molecules and morphology 总被引:13,自引:3,他引:10
Complete coding regions of the 18S rRNA gene of an enteropneust
hemichordate and an echinoid and ophiuroid echinoderm were obtained and
aligned with 18S rRNA gene sequences of all major chordate clades and four
outgroups. Gene sequences were analyzed to test morphological character
phylogenies and to assess the strength of the signal. Maximum- parsimony
analysis of the sequences fails to support a monophyletic Chordata; the
urochordates form the sister taxon to the hemichordates, and together this
clade plus the echinoderms forms the sister taxon to the cephalochordates
plus craniates. Decay, bootstrap, and tree-length distribution analyses
suggest that the signal for inference of dueterostome phylogeny is weak in
this molecule. Parsimony analysis of morphological plus molecular
characters supports both monophyly of echinoderms plus enteropneust
hemichordates and a sister group relationship of this clade to chordates.
Evolutionary parsimony does not support chordate monophyly.
Neighbor-joining, Fitch-Margoliash, and maximum-likelihood analyses support
a chordate lineage that is the sister group to an
echinoderm-plus-hemichordate lineage. The results illustrate both the
limitations of the 18S rRNA molecule alone for high- level phylogeny
inference and the importance of considering both molecular and
morphological data in phylogeny reconstruction.
相似文献
496.
The adsorption of ferritin from a water solution to a hydrophobic methylised quartz surface was studied by transmission electron microscopy, allowing direct examination of the iron core of the molecule without further preparation. The initial adsorption was seen to result in small clusters of molecules, the number of sites/cm(2) being concentration dependent. The adsorption process continued via cluster growth. The rate of adsorption increased and the process became mass transport limited. The clusters formed initially had low fractal dimensions (D approximately 1.0) and a coordination number, cn of 2.6-2.8, which increased with time. These clusters were abruptly restructured at a coordination number of 3.5, and the apparent rate of adsorption decreased during the reorganisation of the adsorbed layer. Finally, an equilibrium level was reached which was stable for at least 24 h. The distribution of ferritin molecules at equilibrium was in clusters with a fractal dimension of D = 1.14 +/- 0.16 and D= 1.33 +/- 0.08, respectively, for ferritin concentrations in the bulk of 10 and 100 microg/ml. Rinsing of adsorbed ferritin layers with buffered salt solution resulted in a rapid transient condensation of the clusters, but the net dissociation of protein was slow with the rate of dissociation being proportional to the logarithm of time. The condensed clusters were slowly restructured to linear polymers of ferritin molecules with a coordination number of 1.9 after 24 h of rinsing. The dissociation of protein molecules continued slowly for more than 3 days of rinsing. The results of the present study indicate that the rate of protein adsorption and desorption is strongly related to the supramolecular structure of the adsorbed protein film. Dense clusters of protein are not stable and this phenomenon may explain the formation of a dynamic equilibrium in spite of the fact that protein adsorption to a solid phase may appear to be practically irreversible. 相似文献
497.
Polymerization of DNA fragments in a head-to-tail arrangement provides a convenient way to obtain multimeric expression of a specific gene product, e.g., epitope-carrying peptides for immunological studies. A novel technique for the polymerization and assembly of peptides has been developed, involving the use of the class-IIS restriction enzyme BspMI which enables unidirectional insertion of the DNA fragments to be polymerized [Kim and Szybalski, Gene 71 (1988) 1-8]. One or several DNA fragments are polymerized in subsequent steps, using in vitro DNA polymerization, and the obtained gene constructs containing several repeats are screened and sequenced using polymerase chain reaction techniques. Using a two-step polymerization strategy a peptide, comprising two repetitive sequences from the Plasmodium falciparum malaria blood-stage antigen Pf155/RESA, was assembled and subsequently synthesized in Escherichia coli. Two different fusion proteins suitable for affinity purification were produced using a dual affinity system. Rabbits were immunized with one of the fusion proteins and the antibody response was analyzed by the enzyme-linked immunosorbent assay and immunofluorescence using the second fusion protein. 相似文献
498.
Mannitol is widely used as a therapeutic agent in the management of acute renal failure. We sought to determine whether mannitol influences the trapping of red blood cells (RBCs) in renal microvasculature, as measured from the distribution of 51Cr-labelled RBCs, in the rat kidney after ischaemia. The results indicate that administration of hyperosmolar mannitol after an ischaemic insult increases RBC trapping in the outer renal medulla in a dose-dependent manner. This was found to occur even though parameters of nephron function were unaffected or even improved. 相似文献
499.
Christine Ruta Arne Nygren Vincent Rousset Per Sundberg Annie Tillier Helena Wiklund & Fredrik Pleijel 《Zoologica scripta》2007,36(1):99-107
We assess phylogenetic relationships within the polychaete family Hesionidae from morphological data combined with nucleotide data from 18S rDNA, 28S rDNA, 16S rDNA and COI. Parsimony and Bayesian analyses were performed on two data sets; the first was based on a more restricted set of terminals with both morphological and molecular data (17 ingroup terminals), while the second included additional taxa with morphological data only (25 ingroup terminals). The different sets of terminals yielded fully congruent results, as did the parsimony and the Bayesian analyses. Our results indicate high levels of homoplasy in traditionally used morphological characters in the group, and that Hesioninae, Gyptini and Gyptis are nonmonophyletic. Hesionini (mainly Hesione and Leocrates ), Psamathini (mainly Hesiospina , Micropodarke , Nereimyra , Psamathe and Syllidia ), Ophiodrominae (Gyptini and Ophiodromini) and Ophiodromini (mainly Heteropodarke , Ophiodromus and Podarkeopsis ) are monophyletic and agree with previous classifications, and Hesionini is probably the sister to all other hesionids. The placements of the small hesionids capricornia and Lizardia , the hydrothermal vent taxa Hesiodeira and Hesiolyra , and the newly described Hesiobranchia , remain uncertain. 相似文献
500.