多倍体银鲫克隆多样性和双重生殖方式的遗传基础和育种应用

单性物种一般是多倍体,且通过单性生殖方式如雌核生殖、杂种生殖或孤雌生殖繁殖.与其他单性和多倍体物种相比,银鲫具有更高的倍性,为六倍体.它经历了几轮连续的基因组多倍化,还经历了一次额外的、在较近年代发生的基因组复制事件.更为重要的是,银鲫已被证实同时存在雌核生殖和有性生殖双重生殖方式.本文综述了银鲫的多倍化起源、克隆多样性和双重生殖方式的遗传基础,概述了其新品种培育和有关其生殖与早期发育相关基因鉴定的研究进展.已有实验证据表明,银鲫正处于二倍化的进化轨道中.作为一个新的进化发育(Evo-Devo)生物学模型,重点论述了银鲫在重复基因的功能歧化和单性动物的有性起源和进化等方面的研究前景.     

单性脊椎动物的生殖方式

单性脊椎动物具有三种不同的生殖方式,即孤雌生殖、雌核生殖以及杂种生殖。本文比较了这三种生殖方式的异同,概述了各自配子发生的细胞学机制。     

韭菜迟眼蕈蚊的性别分化及其生态与进化意义

性别分化是遗传学、进化生物学和生殖行为生态学研究的重要领域之一,对于研究生物的遗传与进化关系、分析生物种群数量动态具有重要意义。对韭菜迟眼蕈蚊BradysiaodoriphagaYangetZhang的性别分化研究结果表明,韭菜迟眼蕈蚊的生殖对策主要以产单性别方式为主,其次是产优势性别方式,2种方式占92%,且产雌产雄的比例基本呈对称现象。用雌雄试虫都来自单性别的种群,连续繁殖3代,其性别分化如同上述,每一代种群的性比基本保持在1∶1。用双性别后代雌虫所产的雌雄虫进行近亲繁殖,连续繁殖3代,结果表明双性别后代的比例明显增大。鉴于以上实验结果,对韭菜迟眼蕈蚊生殖对策的生态与进化意义进行了分析。     

逆转座子对灵长目动物基因组结构的影响

逆转座子(retroposon)是动物基因组中一类可移动的元件,它们首先通过转录产生一个RNA拷贝,然后利用逆转录酶将该RNA拷贝逆转录为c DNA后,再插入到基因组的新位点上。逆转座子在动物基因组中含量极为丰富,种类也很繁多,并随着动物进化在基因组中不断扩增。它们可通过形成插入突变、侧翼序列转导、基因逆转座、DNA断裂与修复、异常重组等机制对动物基因组结构的稳定性产生重要影响,并成为推动基因组进化的重要动力。本文综述了灵长目动物主要的逆转座子类型及其对基因组结构的影响方式,从而为深入理解逆转座子在灵长目动物基因组中的功能及灵长目动物的进化提供参考。     

植物进化与物种绝灭现象

物种绝灭现象在自然界是普遍存在的,绝灭因素是多种多样的,的绝灭和进化是生物发展史上的两个重要方面,进化表现出连续,而绝灭表现出间断,后者对植物进化具有重要意义。     

人类基因组中突变对紧邻碱基的依赖性与重组率

减数分裂重组通过基因转变、碱基替换等方式影响基因组进化。紧邻碱基对突变偏好性有很强的影响,但该“紧邻碱基效应”如何随重组率变化有待深入研究。本文提出基于条件互信息(Conditional mutual information)量化突变对紧邻碱基依赖性的方法,并利用人类SNP等相关数据,分析重组率如何影响突变对紧邻碱基的依赖性。结果表明:在全基因组水平上, SNP位点上的突变对紧邻碱基的依赖性(即平均条件互信息)随着重组率的增加而增加;具体而言,当SNPs两侧碱基为A/G、C/G或C/T时,随着重组率的增加突变偏向性增强,但两侧碱基为A/A或T/T时,重组率对SNP突变偏向性产生抑制作用;另外,重组率越高,外显子与基因间区SNP的突变偏好性越强;而内含子区域SNP的突变偏好受到高重组率的抑制。结果有助于深入理解减数分裂重组如何影响基因组进化。     

低能N~+注入介导的沙漠寡营养细菌基因组SNP研究

为了深入认识低能N~+注入对细菌基因组的进化与突变的作用,本研究在低能N~+注入介导外源基因转化沙漠寡营养细菌DOB150的基础上,通过生物信息学方法对3株重组突变的DOB基因组的单核苷酸多态性进行了分析,共发现192 357个SNP位点。其中重组突变菌株DOB073和DOB113的SNPs类型和数量基本相等,而重组突变菌株DOB981的SNPs类型丰富且数量大。DOB073和DOB113基因组中SNP数目约为0.005个/kb,DOB981约为37.620个/kb。在3株重组突变菌的基因组的SNPs中,AG转换所占比例均为最高。根据SNPs绘制的DOB基因组系统发育树显示,重组突变菌株DOB981的进化速度快于DOB073和DOB113。     

一个孑遗类群-尖舌苣苔族(Klugieae)物种的居群绝灭速率及其指示意义

本文通过对尖舌苣苔族(Klugieae)的5个属中12个种59个地方居群消长动态的统计分析,计算了该族各属物种的居群绝灭速率。在120年的时间区间内,尖舌苣苔族物种的居群绝灭速率和生境受破坏程度呈正相关。显然,一个类群物种的居群绝灭速率对于该类群分布地区环境的受破坏程度具有较强的指示意义。尖舌苣苔族各属物种的居群绝灭速率与其系统发育年龄和进化程度密切相关。进化水平较低,即系统发育上比较原始的类群,其居群绝灭速率往往较高;进化水平较高,即系统发育上比较年青的类群,其居群绝灭速率则低。地区性特有类群,尤其是特有属更容易遭受绝灭的危险。藉此,可在短时期内比较准确地了解该类群的濒危过程。     

酶分子体外定向进化的研究进展

分子体外定向进化是改造酶分子的新策略,它主要通过体外模拟自然进化机制,利用基因随机突变、重组和定向筛选技术,使进化过程朝着人们需要的方向发展。简要介绍了酶分子体外定向进化的发展历史,详细介绍了突变文库构建和筛选方法的最新研究进展及应用情况。     

激光诱发家蚕孤雌生殖的研究：Ⅲ单性一号及单性二号性状表现

采用CO_2激光扩束辐照诱发家蚕孤雌生殖,从获得的单性蚕中,选择出单性一号和单性二号两个类型,单性一号由血色限性突变为斑纹限性,体质强健好养,单性二号仍保持亲本的血色限性,但茧丝质有了提高。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.