DNA Complementary to Ribosomal RNA: Relation between Genomic Proportion and Ploidy

Ten Nicotiana species were assayed for the proportion of DNA that is complementary to ribosomal RNA. This proportion varies from 0.27 to 0.9 percent, with tetraploid species having lower values than the diploid species. The tetraploid species have about twice as much DNA per cell as do diploid species. Thus, the absolute number of genes for ribosomal RNA varies less than the proportion of complementary DNA. Further, the number of genes for the RNA in 80S ribosomes varies less among species than does that for the RNA in 70S ribosomes. The data indicate that loss of DNA complementary to ribosomal RNA is associated with tetraploidy in the genus Nicotiana.     

Replicating form of a single-stranded DNA virus: isolation and properties

The replicating form of single-stranded DNA virus has been isolated in pure form by chromatography on columns of methylated albumin. Its buoyant density in CsCl and "melting temperature" are characteristic of a double stranded DNA structure containing 43 percent guanine-cytosine. The nearest neighbors to uridylate were compared in the RNA synthesized when replicating-form DNA and mature single-stranded DNA were employed as templates in an in vitro system. The mature DNA component of the replicating duplex does not serve as the sole source of complementary RNA. The results agree best with the assumption that both strands of the replicating form function as templates. It is important to note that this is contrary to the situation found in the intact cell where only one of the two strands appears to be transcribed into message.     

Inactivation by nitrogen mustard of single- and double-stranded DNA and RNA bacteriophages

Nitrogen mustard inactivates bacteriophage containing single-stranded DNA and RNA as well as double-stranded DNA. Inactivation may occur by intrastrand cross-linkage in DNA or RNA as well as by interstrand crosslinkage between complementary strands of DNA.     

一种快速高效适于柑桔AFLP分析的DNA提取方法

利用改进的CTAB法提取了柑类、桔类、橙类及部分柑桔杂交实生后代等120多个品种的基因组,结果表明:该方法提取的DNA溶液无色透明,紫外分光光度计测得A260/A280为1.8～1.9,1%琼脂糖凝胶电泳为清晰的一条带,RNA去除干净,无降解现象,DNA的纯度和质量能满足AFLP分析要求.     

一种有效的沙棘总RNA提取方法

高质量RNA的提取是分子生物学和基因工程研究的必要前提.以盐胁迫过的沙棘叶片为实验材料,建立了一种有效的沙棘总RNA提取方法.该方法提取的沙棘总RNA得率较高,平均为213.94 μg/g(鲜叶),RNA的完整性好,纯度较好,利用丙酮和KAc有效的消除了多糖、多酚和黄酮的干扰.反转录实验证明,所提取的沙棘总RNA具有较强的反转录活性,能够运用到后续的分子生物学研究中.研钵等实验用品采用酒精燃烧的方式去除外源RNase,并且药品都是常规试剂,大大的节省了实验时间和降低了实验成本.     

蛋白激发子产生菌链格孢(Alternaria spp.)JH505菌株分子系统学研究

在传统真菌形态学分类研究的基础上,运用遗传学、分子生物学研究手段,结合生物信息学方法对具有诱导植物增产抗病的蛋白激发子产生菌链格孢(Alternaria spp.)JH505菌株进行了分子系统学研究.克隆了该菌株长度为1 267bp的rDNA序列.结果表明,rDNA包含部分18S rRNA、28S rRNA序列及完整的5.8S rRNA、转录外间隔区(ITS1、ITS2)rRNA序列,与A.tenuissima、A.cinerariae、A.dianthi、A.brassicae、A.zinniae相应的rDNA分别具有100%、98%、97%、97%和96%的相似性.结合菌落形态、孢子特征以及rDNA分析.鉴定该菌株为细极链格孢菌(A.tenuissima).     

Chloroquine: mode of action

The drug chloroquine is bactericidal for Bacillus megaterium; it inhibits DNA and RNA biosynthesis and produces rapid degradation of ribosomes and dissimilation of ribosomal RNA. Inhibition of protein synthesis is also observed, evidently as a secondary effect. Inhibition of DNA replication is proposed as a general mechanism of the antimicrobial action of chloroquine.     

水稻RNA纯化方法的比较和改进

本实验利用TRIZOL试剂提取水稻苗期叶片总RNA,对三种常用的RNA纯化方法和改进的纯化方法进行了比较。通过凝胶电泳、紫外分光光度法和RT-PCR法检测提取的RNA样品的品质,结果表明,应用改进的RNA纯化方法可有效去除水稻RNA中的DNA污染,电泳条带清晰无降解;OD260/OD280为1.91~1.98,具有较高的纯度;改良方法纯化的RNA逆转录为cDNA,作为PCR扩增的模板,以不同的循环数进行扩增,在反应适宜循环数内检测不到DNA片段污染,说明用改进方法提取的RNA,其质量和纯度可以满足下一步分子生物学研究的需要。     

豌豆种子发育过程中DNA和RNA含量的动态变化

对豌豆种子发育过程中核酸含量的动态变化研究结果表明：豌豆开花后单粒ＤＮＡ，ＲＮＡ含量，单粒鲜重的变化均呈Ｓ型曲线，开花后第２１天，ＲＮＡ含量达最高峰，拖尾现象消失而趋于单一带区，ＤＮＡ的迁移率也降到最低，从而确定，豌豆开花后第２１天是基因转录活动降低的转折点。     

Small nuclear RNA U2 is base-paired to heterogeneous nuclear RNA

Eukaryotic cells contain a set of low molecular weight nuclear RNA's. One of the more abundant of these is termed U2 RNA. The possibility that U2 RNA is hydrogen-bonded to complementary sequences in other nuclear RNA's was investigated. Cultured human (HeLa) cells were treated with a psoralen derivative that cross-links RNA chains that are base-paired with one another. High molecular weight heterogeneous nuclear RNA was isolated under denaturing conditions, and the psoralen cross-links were reversed. Electrophoresis of the released RNA and hybridization with a human cloned U2 DNA probe revealed that U2 is hydrogen-bonded to complementary sequences in heterogeneous nuclear RNA in vivo. In contrast, U2 RNA is not base-paired with nucleolar RNA, which contains the precursors of ribosomal RNA. The results suggest that U2 RNA participates in messenger RNA processing in the nucleus.     

Structural basis of transcription: separation of RNA from DNA by RNA polymerase II

The structure of an RNA polymerase II-transcribing complex has been determined in the posttranslocation state, with a vacancy at the growing end of the RNA-DNA hybrid helix. At the opposite end of the hybrid helix, the RNA separates from the template DNA. This separation of nucleic acid strands is brought about by interaction with a set of proteins loops in a strand/loop network. Formation of the network must occur in the transition from abortive initiation to promoter escape.     

适合核桃AFLP分析用的DNA提取方法研究

为从核桃叶片中提取高质量的基因组总DNA,比较了9种DNA提取方法。结果表明,改良的CTAB法9提取的DNA溶液无色透明,紫外分光光度计测得A260/A280为1.8~2.0,用0.8%琼脂糖胶电泳,为一条清晰的带,蛋白、多糖、酚类物质、RNA等去除较彻底,DNA无降解现象,该DNA能够适应AFLP分析的要求。     

Reactivity in vivo of the carcinogen N-hydroxy-2-acetylaminofluorene: increase by sulfate ion

Injections of sulfate ion in rats given the carcinogen N-hydroxy-2-acetylaminofluorene increased (i) the formation of 1-and 3-(methion-S-yl)-2-acetylaminofluorene bound to protein in the liver, (ii) the formation of fluorenyl derivatives bound to total protein, ribosomal RNA, and DNA in the liver, and (iii) the toxicity of the carcinogen. These data provide evidence that the highly reactive ester 2-acetylaminofluorene-N-sulfate, previously suggested as an ultimate reactive and carcinogenic metabolite of N-hydroxy-2-acetylaminofluorene, is formed in the rat liver in vivo.     

A computational screen for methylation guide snoRNAs in yeast

Small nucleolar RNAs (snoRNAs) are required for ribose 2'-O-methylation of eukaryotic ribosomal RNA. Many of the genes for this snoRNA family have remained unidentified in Saccharomyces cerevisiae, despite the availability of a complete genome sequence. Probabilistic modeling methods akin to those used in speech recognition and computational linguistics were used to computationally screen the yeast genome and identify 22 methylation guide snoRNAs, snR50 to snR71. Gene disruptions and other experimental characterization confirmed their methylation guide function. In total, 51 of the 55 ribose methylated sites in yeast ribosomal RNA were assigned to 41 different guide snoRNAs.     

Chromosome localization of highly repetitive human DNA's and amplified ribosomal DNA with restriction enzymes

Restriction endonucleases cut and partially removed DNA throughout fixed air-dried human metaphase chromosomes. Some enzymes produced a G-banding pattern; some revealed the presence of multiple chromosome-specific classes of highly repetitive DNA in C-band heterochromatin. Enzymes that produced the informative C-band patterns had recognition sequences that were four or five, but not six, base pairs long and did not contain a cytosine-guanine doublet. In both rat and human chromosomes, regions containing amplified ribosomal RNA genes were specifically removed by the restriction endonuclease Msp I.     

TRANSCRIPTION IN VIVO OF DNA FROM BACTERIOPHAGE SP8

The DNA of bacteriophage SP8, when denatured, yields two components differing in buoyant density in cesium chloride gradients and separable by chromatography on a column of methylated bovine serum albumin and kieselguhr. The denser of the two strands (H) contains more pyrimidines and fewer purines than the lighter (L) strand. Only the H strand forms hybrids with the RNA synthesized by the infected host. The L strand is capable of annealing with complementary RNA synthesized in vitro with it as primer in reactions catalyzed by RNA polymerase. During the vegetative development of phage, host-specific messenger RNA is also synthesized.     

适于AFLP分析用的桃韧皮部DNA提取方法

[目的]研究适于AFLP分析用的桃韧皮部DNA提取方法,为冬季无法获得幼叶和其他幼嫩材料时从事桃基因组研究打下了基础。[方法]以8种野生桃冬季1年生休眠枝的韧皮部为试验材料,采用改进的CTAB法提取基因组总DNA,与其相应幼叶DNA的提取效果进行了比较分析,并进行了AFLP验证分析。[结果]从野生桃韧皮部提取的DNA除产量低于幼叶外,DNA纯度和完整性都较好,OD260/OD280均为1.8~2.0,无降解现象,RNA去除干净,能被限制性内切酶完全消化,其AFLP分析条带清晰,多态性好。[结论]该法提取的野生桃韧皮部基因组总DNA完全适于AFLP分析。     

荒漠拟步甲科昆虫总RNA的有效提取及电泳图谱分析

[目的]获得高质量的总RNA是开展分子生物学研究的重要一步,由于不同生物的机体组成成分有较大差异,需要针对不同类型的物种建立各自有效的RNA提取方法.鞘翅目昆虫富含几丁质的外壳,常规方法难以获得高质量的RNA.[方法]以鞘翅目拟步甲科昆虫小胸鳖甲(Microdera punctipennis)为例,采用TRIzol试剂提取分离总RNA,方法略有改进,并对总RNA的电泳谱带特征进行鉴定.[结果]利用该方法从小胸鳖甲成虫中所获得的总RNA纯度较高完整性好,进一步实验证明提取的总RNA可满足RT-PCR等多种后续实验.琼脂糖凝胶电泳分析表明,其总RNA电泳谱带主要以18S带为主,28S则很弱.[结论]该提取方法对其他荒漠拟步甲科昆虫,尤其是含几丁质外壳的甲虫总RNA提取具有指导作用,小胸鳖甲总RAN的电泳谱带与哺乳动物肿瘤细胞的不同.