"物种的形成"的教学设计

1 教学目标 1.1 知识与技能1 1)阐明并解释物种、隔离等相关概念. 2)运用所学概念分析物种形成的过程. 3)概述物种形成的主要环节以及各环节对于物种形成的作用.     

Rapid and efficient selection of recombinant site-directed mutants of Bradyrhizobium japonicum by colony hybridization

Abstract Due to the high incidence of spontaneous antibiotic resistance and slow growth of Bradyrhizobium japonicum strains, screening for site-directed mutants is cumbersome and time-consuming. A rapid method for selection of recombinant site-directed mutants of B. japonicum was developed. A kanamycin (Km) and a spectinomycin (Sp) cassette were each used to replace DNA fragments in the chromosome by homologous recombination. The primary new features of this method involve a simple plate selection for the antibiotic (Km or Sp) resistant mutants, then colony streaking, and lysis for DNA hybridization on a nitrocellulose filter enabling direct identification of the recombinant site-directed mutants. This method has permitted us to quickly and easily identify a large number of positive recombinant mutants from a large number of indicidual colonies. The procedure eliminates the need to first isolate genomic DNA from each mutant for Southern hybridization. All of the tested site-directed mutants from this method were confirmed to exhibit the expected mutant phenotype.     

News & Notes: Isolation of Vibrio harveyi from Diseased Kuruma Prawns Penaeus japonicus

Outbreaks of high mortality among the cultured kuruma prawn Penaeus japonicus without overt gross signs occurred during August and December of 1994 in I-Lan, Taiwan. Eleven luminous bacterial strains were isolated from the hepatopancreas of moribund prawns from five different farms by use of tryptic soy agar (TSA, supplemented with 2% NaCl) and/or thiosulfate citrate bile salt sucrose (TCBS) agar. These strains, together with our two previously unpublished isolates, were characterized and identified to be Vibrio harveyi in comparison with two ATCC Type strains and one strain previously isolated from the tiger prawn, P. monodon. Received: 22 November 1995 / Accepted: 24 February 1996     

Dcaf11 activates Zscan4-mediated alternative telomere lengthening in early embryos and embryonic stem cells

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Field Evidence for Bioluminescent Signaling in the Pony Fish, Leiognathus elongatus

Luminescence of the pony fish, Leiognathus elongatus, was observed in the natural environment during nighttime diving. The light was emitted from the lateroventral portion of the body, as bright rectangular-shaped luminescence patches turned on and off periodically. Luminescent fish had a distinct clear patch on the flank through which light was emitted, whereas non-luminous fish did not have such a clear patch. Both luminous and non-luminous fish were found within a shoal, where non-luminous individuals were chased by luminous ones. From previous morphological studies, the luminous and non-luminous individuals are likely to be male and female, respectively. Our observations provide field evidence that the luminescence functions as intraspecific communications in L. elongatus.     

Establishment of a cell line derived from top-minnow (Gambusia patruelis)

A cell line, derived from top-minnow (Gambusia patruelis), has been transferred for 114 times in Leibovitz L-15 medium plus 10% FCS (GM-L-15) at a temperature of 31 degrees C and designated as TM. The results of a chromosome analysis of 100 cells at the metaphase stage, show a bimodal distribution of the chromosome number ranged from 21 to 68 with a modal number of 38. At a low seeding density, the plating efficiency of TM cells was 11-12.4%. TM cells are susceptible to EVE, EVA, EVEX, IPNV and LV-1 at 18 degrees C. The result of a sterility test showed that the TM cell line was free of bacterial, fungal and mycoplasmic contamination. The presence of numerous microvilli on the surface of TM cells in the micrographs of normal TM cell. The microvilli are replaced by blebs at the late stage of cytokinesis of the cells.     

Short Report: Tissue-specific Expression Profiles of the Uncoupling Protein Family in Normal Control Mice and Genetically ob/ob Mice

Uncoupling proteins (UCPs) located in the inner mitochondrial membrane are involved in the regulation of energy balance. Thus far, 5 UCP isoforms have been identified, but controversies exist in the research focused on the function of the UCPs (except UCP1) in the pathogenesis of obesity. Because of the known cross-reactivity of the antibodies presently available for the detection of UCP proteins, this study systematically analyzed the differential tissue expression profiles of the 5 UCP isoforms in lean control mice and ob/ob mice by using real-time polymerase chain reaction (PCR) analysis. The results show that the tissue-specific expression patterns of individual isoforms in normal and ob/ob mice are considerably different; this will provide new insights into the functions of UCPs in the pathogenesis of genetic obesity.