It indicated that the chinese isolates belong to north american group . two pairs of different primers of orf7 were used to identify the genotype of prrsv isolates in china , and then compared with the reference isolates of north american and european serotype and modified live prrsv vaccine . the results further proved that prrsv prevalent in china belongs to b genetype . combining the restriction enzyme digestion patterns obtained from mini , hindi and sactt , we observed 2 distinct rflp patterns 在此基础上，扩增各毒株的orf5基因，用mlu , hinc和sac限制性内切酶切割orf5基因，通过这3种限制性内切酶获得了各毒株的orf5基因限制性酶切图谱，经rflp分析表明国内分离毒株与美洲型强毒株有着相同的rflp图谱，而与疫苗毒的rflp图谱存在明显差异，进一步证明国内分离毒株的基因型属于美洲型的强毒株。
Objective : construct high - level expression system of echistatin in e . coli methods : obtain amino - acid sequence of echistatin from genebank database . considering the bias of usage of 61 available aminoacid codons in e . coli , design the coding sequence of echistatin , synthesize the dna sequence chemically , get single copy coding gene and repeated two copy coding gene of echistatin . insert the sequence into expression vector pbv220 , and more , we construct fusion expression clone of echistatin with pcr , identify the recombinant vector by dna sequencing 目的构建蛇毒锯鳞蝰素( echistatin )的原核高效表达体系方法由genebank数据库检索蛇毒锯鳞蝰素( echistatin )的氨基酸序列，结合大肠杆菌蛋白质合成体系对氨基酸密码子使用的偏爱性，设计了echistatin编码基因，体外人工合成编码基因dna片段，通过适当的限制性内切酶位点插入表达载体pbv220 ，分别构建了echistatin的单拷贝表达克隆、双拷贝串联表达克隆；进一步通过pcr技术构建echistatin的融合表达基因克隆。
Other chromosome elements , telomere and ars , have also been cloned for constructing artificial chromosome . arabidopsis telomere was cloned from pcr products using telomere repeat primers without other template . a 2000bp fragment of ars was released from arabidopsis genomic bac clone t14a4 by claidigestion and subcloned into clai digested pbluescript 拟南芥的端粒是利用端粒的重复序列进行无模板的pcr扩增得到的；约2000bp的ars片段是从拟南芥的bac克隆t14a4中用限制性内切酶c1a1切下，然后亚克隆到通用载体pbluescript上。
Two positive clones were sequenced , and the results showed that its nuclcotidc sequence includes an open reading segment which codes for a 45 - amino acids protein and three endonuclcase sites which arc1 bgii , bamh i and bgi ii , this protein was identified as metallothionein based on its characteristic described above and its similarity ( 85 % ) to the mtn gene of drosophila : the 10 cysteine residues present occur in five pairs of cys - x - cys , x is serine , valine , ilistidine or lysine 结果显示：扩增的cdna片段长度为289bp ，其中含有一个编码45个氨基酸的开放阅读框，阅读框所编码的氨基酸中含有10个半胱氨酸，且在序列中均排列成cys - x - cys ，其中x为ser 、 val 、 his或lys 。这些特征说明扩增的基因片段为家蝇mt基因序列的一部分。此基因序列片段与果蝇mtn基因序列的同源性达到85 . 0 ，扩增的基因序列中含有三个内切酶位点bg 、 bam和bg ，这一点也和果蝇mtn基因十分相似。
I and hindlll respectively . after the digested products were run via agarose gel electrophoresis and transferred into nylon membrane , the southern blot was carried out using the cdna of rubber tree etrl as probe . the result of the southern blot showed that a hybridization band ( - 3 . 0kb ) turned up from the ecor i digested product and another band ( - 4 . 8kb ) turned up from the hindi ] 从橡胶树pr107品系的嫩叶提取基因组dna ，用限制性内切酶ecor 、 hinofll分别酶切，琼脂糖凝胶电泳分离并转膜后，用克隆的橡胶树etri基因的cdna片段作探针进行southern杂交分析，结果表明， ecor酶切在约3 okb处有一条杂交带出现， hi 。
Sinensis and e . j . hepuensis has been found in the sequences of the portions of 16s rdna and pcr / rflp studies of 110 samples , from six river valleys in eastern mainland of china . these subspecies - specific restriction sites allow rapid discrimination with the endonuclease dra i , and therefore can be used as a diagnostic genetic marker for identification of the two subspecies 通过对中国大陆东部6个水系110个绒螯蟹个体16srdna部分序列的测定和pcr rflp分析，发现在合浦绒螯蟹与中华绒螯蟹之间存在3 4个固定的碱基替代，这种亚摘要种特异性的限制性位点可以通过限制性内切酶dra进行快速检测，成为2个亚种的分子鉴定标记。
With h . trueperi genomic dna and degenerate primers , a 560 bp pcr fragment was obtained and labeled as a probe . after h . trueperi genomic dna was digested with different endonucleases , southern blot result showed a 2 . 6 kb positive fragment digested by ecori and ipcr was carried out to obtain the flanking sequence 将扩增片段用地高辛标记成探针，与用不同限制性内切酶完全酶切的h . trueperi总dna片段作southem杂交，结果显示在ecori酶切片段的2 . 6kb处有阳性信号。
