大麦条纹花叶病毒新疆株(BSMV-XJ)RNA_2的cDNA克隆及5′端序列分析

分离了大麦条纹花叶病毒(BSMV)新疆株基因组的3个RNA组份。以RNA2为模板,3′端互补寡核苷酸为引物,合成了第一条cDNA链和第二条cDNA链,将ds-cDNA重组在pUC9质粒中,转化大肠杆菌细胞,获得含RNA3′端的克隆,并证明所选克隆的cDNA含有新疆株几近全长的RNA2组份。对于插入片段为3.3kbp的112号克隆进行了酶谱分析,得到了与国外典型株类似的结果;用双脱氧终止法分析了相当于RNA 2 5′端250bp的cDNA酶切片段,表明与国外典型株有十分相似的一级结构。     

Evolutionary plasticity in prokaryotes: A panglossian view

Enzyme directed genetic mechanisms causing random DNA sequence alterations are ubiquitous in both eukaryotes and prokaryotes. A number of molecular geneticist have invoked adaptation through natural selection to account for this fact, however, alternative explanations have also flourished. The population geneticist G.C. Williams has dismissed the possibility of selection for mutator activity on a priori grounds. In this paper, I attempt a refutation of Williams' argument. In addition, I discuss some conceptual problems related to recent claims made by microbiologists on the adaptiveness of molecular variety generators in the evolution of prokaryotes. A distinction is proposed between selection for mutations caused by a mutator activity and selection for the mutator activity proper. The latter requires a concept of fitness different from the one commonly used in microbiology.     

Nucleotide Sequence Surrounding the Locus Marker D21S246 on Human Chromosome 21

Most ofthe human Not I linking clones identified to date areconsidered to be derived from CpG islands because ofthe recognitionsequence of this enzyme, and CpG islands have been reportedto be located around the 5' regions of genes. As a pilot study,we determined the complete nucleotide sequence (41,924 bp) ofa human cosmid clone (LL21NC02Q7A10) containing the marker D21S246originating from a Not I linking clone. As a result of sequenceanalysis, we successfully mapped and revealed the genomic genestructure for KIAA0002 previously reported as a cDNA clone.This gene consists of 15 exons and was shown to exist at theD21S246 locus on human chromosome 21q21.3–q22.1. Theseresults demonstrated that genomic marker-anchored DNA sequencingis a useful approach for the human genome project.     

Results and recommendations

In the first phase of a collaborative study by the International Programme on Chemical Safety (PRCS), four coded chemicals, i.e. azidoglycerol (AG, 3-azido-1,2-propanediol), methyl nitrosurea (MNU), sodium azide (NaN₃) and maleic hydrazide (MH), and ethyl methanesulfonate (EMS) as a positive control were tested in four plant bioassays, namely the Arabidopsis embryo and chlorophyll mutation assay, the Tradescantia stamen hair assay (Trad-SH assay), the Tradescantia micronucleus assay (Trade-MCN), and the Vicia faba root tip assay. Seventeen laboratories from diverse regions of the world participated with four to six laboratories each using one plant assay. For the Arabidopsis assay, laboratories were in agreement with MNU and AG giving positive responses and NaN₃ giving a negative response. With the exception of one laboratory which reported MH as weakly mutagenic, no mutagenic response was reported for MH by the other laboratories. For the Vicia faba assay, all laboratories reported a positive response for MNU, AG, and MH, whereas two of the six laboratories reported a negative response for NaN₃. For the Trad-SH assay, MH was reported as giving a positive response and a positive response was also observed for MNU with the exception of one laboratory. NaN₃, which exhibited a relatively high degree of toxicity, elicited a positive response in three of the five laboratories. AG was found positive in only one of the two laboratories which tested this chemical. For the Trad-MCN assay, MNU and MH were reported as positive by all laboratories, while four out of five laboratories reported NaN₃ to be positive. Only one of three laboratories reported AG to be positive. The major sources of variability were identified and considered to be in the same range as found in similar studies on other test systems. Recommendations were made for minor changes in methodology and for initiating the second phase of this study.     

A physical map and clone bank of the black pine (Pinus thunbergii) chloroplast genome

Black pine chloroplast DNA is 119,707 bp long. The physical map is shown and the genes are listed. Plasmid clones covering the entire DNA sequence have been ordered and available upon request.     

Influence of growth rate on pigment and lipid composition of the microalgaIsochrysis aff.galbana clone T.iso

A continuous culture ofIsochrysis aff.galbana clone T.iso, used to feedPecten maximus larvae at IFREMER (Brest, France), was carried out in a chemostat at its optimum temperature for growth (26 °C). Changes in pigments, lipid class (neutral, glyco- and phospholipids) and degree of fatty acid unsaturation were studied at three different growth rates (0.33, 0.5, 1 d^–1). As predicted by chemostat theory, a slow growth rate produced higher cell numbers and higher biomass per unit volume. These cells were low in chlorophylla and carotenoids, but rich in neutral lipids. In contrast, cultures with a fast growth rate yielded lower cell concentrations, buth higher chlorophylla, carotenoid and membrane lipid contents per cell. Changes in polyunsaturated fatty acid distribution were related to differences in algal growth rates. Neutral lipids contained mainly saturated and monounsaturated fatty acids (C18:19) at low growth rates whereas they were enriched in polyunsaturated fatty acids, especially C22:63, at high growth rates. Therefore, it is suggested that the growth rate in continuous cultures be controlled so as to adjust the relative proportions of polyunsaturated fatty acids in lipid classes of the diet meant for larval nutrition.Author for correspondence     

菜用香椿良种选育性状的模糊综合评判

采用模糊数学方法对菜用香棒１６个不同种源的无性系从形态、颜色、香气、抗病性四个方面进行了综合评判,筛选出了接近选育目标的５个菜用优良无性系。