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Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
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Background
In addition to known protein-coding genes, large amounts of apparently non-coding sequence are conserved between the human and mouse genomes. It seems reasonable to assume that these conserved regions are more likely to contain functional elements than less-conserved portions of the genome. 相似文献5.
Removal of surfactant solubilized polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium in a rotating biological contactor reactor 总被引:4,自引:0,他引:4
White rot fungi can oxidize surfactant solubilized polycyclic aromatic hydrocarbons (PAH). The objective of this study was to evaluate the performance of immobilized white rot fungus, Phanerochaete chrysosporium, to remove surfactant Tween 80 solubilized PAH i.e. phenanthrene, pyrene and benzo(alpha)pyrene in a rotating biological contactor (RBC) reactor. Results indicated that the immobilized P. chrysosporium in the RBC reactor system in continuous operation could effectively remove the three tested PAH at specific hydraulic loading rates and concentrations tested for each individual PAH. Batch operation of RBC reactor showed that the immobilized P. chrysosporium was stable and effective for the eight successive batch treatments of PAH in solution medium i.e. PAH removal was greater than 90% after 60 h, although only low levels of ligninolytic enzyme activity were detected. The removal of phenanthrene and pyrene in solution medium has been found to be a first order reaction in batch operation. A mass balance calculation indicated that biological oxidation was the main factor for removal of benzo(alpha)pyrene i.e. 95.7% in the RBC reactor. However, for phenanthrene and pyrene, both biological oxidation (i.e. 49 and 56%, respectively) and RBC disc foam adsorption (i.e. 44 and 34%, respectively) made a significant contribution to the removal of PAH. 相似文献
6.
van Dijken JP Bauer J Brambilla L Duboc P Francois JM Gancedo C Giuseppin ML Heijnen JJ Hoare M Lange HC Madden EA Niederberger P Nielsen J Parrou JL Petit T Porro D Reuss M van Riel N Rizzi M Steensma HY Verrips CT Vindeløv J Pronk JT 《Enzyme and microbial technology》2000,26(9-10):706-714
To select a Saccharomyces cerevisiae reference strain amenable to experimental techniques used in (molecular) genetic, physiological and biochemical engineering research, a variety of properties were studied in four diploid, prototrophic laboratory strains. The following parameters were investigated: 1) maximum specific growth rate in shake-flask cultures; 2) biomass yields on glucose during growth on defined media in batch cultures and steady-state chemostat cultures under controlled conditions with respect to pH and dissolved oxygen concentration; 3) the critical specific growth rate above which aerobic fermentation becomes apparent in glucose-limited accelerostat cultures; 4) sporulation and mating efficiency; and 5) transformation efficiency via the lithium-acetate, bicine, and electroporation methods. On the basis of physiological as well as genetic properties, strains from the CEN.PK family were selected as a platform for cell-factory research on the stoichiometry and kinetics of growth and product formation. 相似文献
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Elizabeth Peacock Sarah A. Sonsthagen Martyn E. Obbard Andrei Boltunov Eric V. Regehr Nikita Ovsyanikov Jon Aars Stephen N. Atkinson George K. Sage Andrew G. Hope Eve Zeyl Lutz Bachmann Dorothee Ehrich Kim T. Scribner Steven C. Amstrup Stanislav Belikov Erik W. Born Andrew E. Derocher Ian Stirling Mitchell K. Taylor ?ystein Wiig David Paetkau Sandra L. Talbo 《PloS one》2015,10(8)
9.
Enzymatic transesterification of waste cooking oil, comprising fats, oil and grease (FOG), to produce fatty acid methyl esters (FAME) i.e. biodiesel, was investigated using a novel strain of the fungus Aspergillus niger, immobilized as a whole‐cell biocatalyst. Response surface methodology (RSM), with a five‐level‐three‐factor central composite rotatable design, was used to optimize the reaction and analyze the relationship of reaction variables and their coinfluent on the response i.e. FAME yield. Independent variables that affect the transesterification reaction include temperature, feedstock water content and enzyme amount. Using RSM, a second‐order polynomial equation was derived for FAME yield using multiple regression analysis. The second‐order polynomial regression model was highly significant (P<0.001) in predicting the actual relationship between the response and the variables, where a linear relationship was apparent between observed and predicted values (R2=0.9651). In addition, the predicted determination coefficient q2 i.e. 0.7723, also proved that the model has a high predictive ability. The validation experiments, under optimized conditions, showed that the predicted value of maximum FAME yield (i.e. 91.3%) was in close agreement with the experimental value (i.e. 91.8%). 相似文献
10.
Anopheles mosquitoes are the primary vectors for malaria in Africa, transmitting the disease to more than 100 million people annually. Recent functional studies have revealed mosquito genes that are crucial for Plasmodium development, but there is presently little understanding of which genes mediate vector competence in the wild, or evolve in response to parasite-mediated selection. Here, we use population genetic approaches to study the strength and mode of natural selection on a suite of mosquito immune system genes, CTL4, CTLMA2, LRIM1, and APL2 (LRRD7), which have been shown to affect Plasmodium development in functional studies. We sampled these genes from two African populations of An. gambiae s.s., along with several closely related species, and conclude that there is no evidence for either strong directional or balancing selection on these genes. We highlight a number of challenges that need to be met in order to apply population genetic tests for selection in Anopheles mosquitoes; in particular the dearth of suitable outgroup species and the potential difficulties that arise when working within a closely-related species complex. 相似文献