Genetic variation inferred from RAPD fingerprinting in three species of tilapia

This study used random amplified polymorphic DNA (RAPD) fingerprinting for estimating genetic variation and species differentiation in three species of tilapia. A 16-mer random primer generated RAPD markers ranging from 250 to 2400 base pairs (bp). Genetic similarity estimates obtained by pairwise comparisons based on the method of Nei and Li (1979) indicated high genetic similarity (mean genetic similarity (± sd), 0.73 (± 0.15) for Nile tilapia; 0.78 (± 0.12) for Mozambique tilapia; and 0.87 (± 0.07) for Aureus tilapia) within each of the tilapia species. The average interspecies genetic similarities obtained among the three species were 0.59 (± 0.07) for Mozambique/Nile tilapia, 0.46 (± 0.09) for Aureus/Nile tilapia and 0.38 (± 0.07) for Aureus/Mozambique tilapia pair. DNA profiles generated in each species of tilapia were unique. A total of 13 RAPD markers differentiating the three species of tilapia were detected. Our study presented RAPD markers as a new class of useful genetic markers for assessment of genetic diversity and species differentiation in tilapia.     

Inheritance and reliability of random amplified polymorphic DNA-markers in two consecutive generations of common carp (Cyprinus carpio L.)

Random amplified polymorphic DNA (RAPD) markers have been used in a variety of genetic studies in fisheries and aquaculture. Most population studies are performed without preliminary data demonstrating the Mendelian inheritance and reproducibility of RAPD markers. In this study, the inheritance and reproducibility of RAPD markers was examined in two consecutive generations of common carp, Cyprinus carpio L. Variability and segregation of RAPD markers were investigated in one F₁ progeny and three F₂ progenies. Seventy-four RAPD markers were generated by five primers using DNA extracted from the initial ornamental (koi) common carp female and wild-type colour common carp male. Fifty-five of these RAPD markers were transmitted to the F₁ progeny and the inheritance patterns were analysed. Twenty RAPD markers were fully reproducible and demonstrated dominant simple Mendelian inheritance patterns in two consecutive generations. Twenty-four RAPD markers were not reproducible in all progenies. Thirteen markers displayed inheritance ratios in the progenies that did not fit simple Mendelian inheritance patterns. Non-reproducibility of RAPD markers and distorted ratios may be caused by the absence of amplification, poor amplification or by the appearance of artefact bands. Random amplified polymorphic DNA markers with poor reproducibility and non-Mendelian inheritance can lead to misinterpretations of data in population studies, resulting in errors in the estimation of genetic diversity within and between individual populations. Therefore, it is recommended to first identify the set of reproducible RAPD markers that demonstrate Mendelian inheritance before application of the RAPD technique in population studies.     

Mineral composition in the holdfast of three brown algae of the genus Laminaria

SUMMARY: The mineral (Na, K, Ca, Mg, Fe, Mn and Zn) contents in the holdfast of three brown algae of the genus Laminaria were determined to compare with those in frond and stipe. The wild and cultivated kelps of Laminaria japonica , L. ochotensis , and L. diabolica were used as samples. The K content was markedly high (11.76–14.91 g/100 g dry weight) in the holdfast of cultivated L. japonica; the K/Na ratio (3.88–5.18) of the holdfast was greater than those of frond and stipe as well as the reported values of frond (1.0–2.2). The content of Ca in the holdfasts of these three species was also higher than those in frond and stipe. The content of Mn showed the same tendency. This is the first report showing that the holdfast of L. japonica and L. diabolica is rich in minerals, especially K.     

鲤鱼的遗传连锁图谱（初报）

建立了鲤鱼的遗传连锁图谱。图谱有ＲＡＰＤ分子标记５６个，鲤鱼的ＳＳＬＰ标记２６个，鲤鱼ＳＳＬＰ标记１９个，斑马鱼的ＳＳＬＰ分子标记７０个，鲤鱼基因标记９１个，共有标记２６２个；图谱有５０个连锁组，连锁图给出鲤鱼的基因组大小在５７８９ＣＭ左右。     

半滑舌鳎DNA的群体遗传变异

采用AFLP、RAPD和线粒体细胞色素b基因(Cytb)片段序列分析技术对半滑舌鳎(Cynoglossus semilaevis)群体遗传变异进行研究。分别采用5对选择性引物和18条随机引物对半滑舌鳎3个群体(黄海野生群体、渤海野生群体、养殖群体)进行分析。AFLP和RAPD分析结果表明,黄海群体的遗传多样性高于渤海群体,养殖群体的遗传多样性最低。利用Shannon多样性指数和基因分化系数进行遗传变异来源估算,结果表明,遗传变异主要来自于群体内。同其他鱼类相比,半滑舌鳎群体遗传多样性水平较低。对黄海、渤海野生群体共37个个体的线粒体Cytb基因片段序列进行分析,共检测出5种单倍型,渤海群体内个体序列完全相同,共享单倍型H1;在黄海群体中除检测到单倍型H1外,还检测到其余4种单倍型。Cytb序列分析结果表明,黄海群体遗传多样性较渤海群体丰富,个体间序列变异很小,个体间核苷酸差异数在0~1之间,两群体间无显著遗传差异。通过比较3种分子标记对半滑舌鳎群体间遗传差异的检测和群体间遗传距离的计算,显示AFLP标记对群体间遗传差异的检测最为灵敏,是一种理想的分子标记。     

4种笛鲷属鱼类随机扩增多态性DNA及遗传多样性研究

使用RAPD技术分析了红鳍笛鲷、紫红笛鲷、勒氏笛鲷和约氏笛鲷的种内遗传多样性、种间遗传多样性和种间亲缘关系。在120个随机引物中筛选出扩增效果好的引物36个，平均每个引物在每个个体上产生7．7个条带。种内遗传多样性研究结果显示：遗传距离(D)分别为0．2257，0．2228，0．2679和0．2247；遗传多样性指数(H)分别为0．1854，0．1904，0．2015和0．1865。说明目前湛江近海这4种笛鲷的遗传多样性比较丰富，它们的种质资源仍处于一个良好的水平。种间遗传多样性结果显示：勒氏笛鲷与约氏笛鲷遗传距离(Dpq)最小，亲缘关系最密切，勒氏笛鲷与红鳍笛鲷种间Dpq最大，亲缘关系最远。     

7种珍珠贝RAPD鉴别标记的初步研究

采用RAPD分子标记技术对珠母贝属的大珠母贝、珠母贝、黑珠母贝、白珠母贝、合浦珠母贝、长耳珠母贝和珍珠贝属的企鹅珍珠贝的基因组DNA的特异性遗传标记进行分析。从21个OPM和S系列中筛选出4个引物,共扩增出57个位点,每条引物平均产生14·3个位点。扩增片段大小在250~2000bp间,平均每种贝每条引物产生4·9条带。其中引物S10对7种珍珠贝的RAPD产物呈现出物种的特异性,可同时将7种珍珠贝分开,其余引物可以将2种或2种以上的珍珠贝区别开来。引物S10可以作为种间鉴定的标记。     

Evaluation of genetic relationship among six Labeo species using randomly amplified polymorphic DNA (RAPD)

Labeo species constitute an important group of fish with intense diversity and potential for commercial aquaculture in many Southeast Asian nations including the Indian subcontinent. The present investigation involves the comparative analysis of randomly amplified polymorphic DNA (RAPD) profiles of six Labeo species viz., L. bata (bata), L. calbasu (calbasu), L. dyocheilus (dyocheilus), L. fimbriatus (fimbriatus), L. gonius (gonius) and L. rohita (rohu) at the nuclear DNA variation level. Fifteen decamer random primers were chosen from 40, which amplified a total of 449 DNA fragments ranging in size from 400 to 3000 bp. Both monomorphic and polymorphic DNA bands were identified based on their presence or absence that could be used for specieswise differentiation. Similarity coefficients were calculated to quantify the genetic variation within and between species. On an average, the highest intra‐species genetic similarity value was found in calbasu (0.93) followed by rohu and fimbriatus (0.91), bata (0.87), gonius (0.86) and dyocheilus (0.77). The interspecies genetic similarity estimates among the species of Labeo were used to deduce their phylogenetic relationships. The cluster analysis showed two main clusters, one with calbasu, rohu, fimbriatus and gonius and another with bata and dyocheilus. The study provides evidence that RAPD could be used for genetic differentiation of closely related species.     

Mitochondrial DNA variation and population structure of the Japanese mitten crab Eriocheir japonica

ABSTRACT:   The Japanese mitten crab Eriocheir japonica is a common grapsid species found throughout freshwater and estuarine regions in Japan. In order to obtain information on the genetic variation and population structure of this species, a polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) analysis was conducted on the cytochrome oxidase subunit I (COI) of mitochondrial DNA, on 666 individuals from 19 sample sites covering the three main geographic regions of Japan (Main Islands, Okinawa, and Ogasawara). Genetic analysis using seven restriction enzymes produced an array of 61 composite haplotypes. Three regional groups corresponding to the three geographic regions were clearly identified by cluster and molecular variance model ( amova ) analyses. Each of the three groups showed dominant haplotypes that were almost completely absent in populations from the other geographic areas. Comparison with published information for other species indicates that the degree of genetic divergence between these three main groups is equivalent to the genetic distance between congeneric species. Thus, the population structure of the Japanese mitten crab, as inferred from mtDNA analysis, is formed by genetically distinct groups that closely reflect their geographic distribution in the Japanese archipelago as well as restricted gene flow.     

中国对虾生长性状相关遗传标记的筛选与克隆

采用随机扩增多态性DNA(RAPD)技术,对中国对虾“黄海1号”快速生长的第6代群体同一养殖池中生长性状发生分离的两个极端群体、海捕的中国对虾对照群体,进行生长相关遗传标记的筛选。采用240个RAPD引物,共产生标记数2156个。筛选出与生长性状相关的遗传标记65个,其中正相关标记55个,负相关标记10个。依据这些标记在群体中出现的频率和变化规律,筛选出9个特异性标记,其中正相关标记7个,负相关标记两个。对这些特异性标记进行序列测定,获得了6个完整的DNA序列(Genebank注册号DQ185932-DQ185937),并将测序结果进行BLAST分析,发现测得DNA的序列与数据库中已注册序列的相似性较低,未能找到同源性较高的功能基因。根据每一序列重新设计引物,已有两个RAPD标记成功转化为稳定的SCAR标记。