形态性状、分子性状与同源性

“同源性（homology）”是生物学中最基本的概念之一。近年来,随着分子生物学、生物信息学、发育生物学以及进化发育遗传学等学科的快速发展,同源性一词在形态性状的比较、核苷酸和氨基酸序列的分析以及探讨形态性状进化的分子机制等方面都有广泛应用。然而,由于不同的研究者对同源性概念的理解有所不同,在实际应用中难免会出现不恰当使用“同源性”一词并得出错误结论的情况。本文从不同的角度介绍了如何对同源性进行判断以及影响同源性判断的因素。并指出正确理解同源性这一概念的含义,以及通过综合各方面的证据对同源性进行推断对于揭示基因型和表型的进化以及二者之间的关系非常重要。     

形态和分子进化研究中的同源概念

在比较生物学中,同源是一个中心概念,是系统学的心脏,同源最基本的意义就是共同祖先。然而,这只是对同源的解释而非告诉我们怎样去发现它。同源又可被看成是特别类群间的联系。形态进化研究中同源比较的对象是生物的结构,而分子进化研究中的同源比较对象是DNA中的核着酸序列,现对这两种层次的同源概念及其相互间的关系进行讨论。       

植物基因家族的分子进化

植物基因家族的分子进化曾庆平,郭勇（华南理工大学生物工程系,广州５１０６４１）关键词基因家族,同源性,分子进化,生物工程建立基因数据库与计算机检索程序使不同基因之间的碱基序列同源性的比较成为可能,同时也有助于进行基因的分子起源与进化以及蛋白质结构与功...     

大熊猫的分子遗传学研究现状

大熊猫作为一种具有明星效应的珍稀濒危动物 ,受到人们的广泛关注和研究。多年来 ,研究工作主要集中在生态、饲养繁殖、分类、形态、疾病及生理生化等领域 ,而分子生物学水平的研究则较少。随着近年来分子生物学相关技术的发展 ,对大熊猫的研究也逐渐深入到分子水平 ,并取得了一些可喜的成果。本文就该领域的研究现状分四个方面 ,即分子进化、遗传多样性、亲子鉴定和个体识别、以及其它方面等作一综述。1　分子进化的研究大熊猫的分类地位 ,一直是困扰众多研究者的一个难题。前期的研究主要是从形态、解剖、化石等方面的知识来进行分类的。…     

分子·形态·进化

分子·形态·进化马德如（南开大学分子生物学研究所,天津３０００７１）关键词异位同形盒,发育,进化最早重视‘异位同形’（ｈｏｍｅｏｓｉｓ）这类发育变异并首创此词的是Ｗ．Ｂａｔｅｓｏｎ。在他１８９４年出版的《关于变异的研究资料》一书中列举的例子有：昆虫生...     

木聚糖酶分子进化的研究进展

木聚糖的降解需要多种水解酶的协同作用,其中βD1,4内切木聚糖酶是最关键的水解酶之一。同一家族木聚糖酶氨基酸序列间有较高的同源性和较近的亲缘关系,这标准通常用于酶的家族归类。不同来源的同种木聚糖酶在相同位置上的氨基酸残基起源于共同祖先或者具有相似的生物学功能,而在进化过程中,对酶分子结构、催化起重要作用的氨基酸残基往往高度保守。综述了木聚糖酶分子进化的研究进展及其应用前景 。     

牙齿发育不全的分子遗传学研究进展

牙齿发育不全是一类十分常见的人类颅面部发育异常.目前的研究表明,其病因与遗传因素、环境因素及后天因素都有关联.加之,牙齿发育的分子遗传学机制已然成为现代分子生物学的研究热点.本文就牙齿发育的简要过程、分子机制和牙齿发育不全的最新分子遗传学研究进展方面作一综述.     

植物分子群体遗传学研究动态

分子群体遗传学是当代进化生物学研究的支柱学科, 也是遗传育种和关于遗传关联作图和连锁分析的基础理论学科。分子群体遗传学是在经典群体遗传的基础上发展起来的, 它利用大分子主要是DNA序列的变异式样来研究群体的遗传结构及引起群体遗传变化的因素与群体遗传结构的关系, 从而使得遗传学家能够从数量上精确地推知群体的进化演变, 不仅克服了经典的群体遗传学通常只能研究群体遗传结构短期变化的局限性, 而且可检验以往关于长期进化或遗传系统稳定性推论的可靠程度。同时, 对群体中分子序列变异式样的研究也使人们开始重新审视达尔文的以“自然选择”为核心的进化学说。到目前为止, 分子群体遗传学已经取得长足的发展, 阐明了许多重要的科学问题, 如一些重要农作物的DNA多态性式样、连锁不平衡水平及其影响因素、种群的变迁历史、基因进化的遗传学动力等, 更为重要的是, 在分子群体遗传学基础上建立起来的新兴的学科如分子系统地理学等也得到了迅速的发展。文中综述了植物分子群体遗传研究的内容及最新成果。     

心脏发育及先天性心脏病的分子遗传学基础

从发育遗传探讨先天性心脏病的发病机制，是目前的研究热点。本文综述了ｈｔｌ、ｎｏｄａｌ、ＨｏｍｅｏｂｏｘＴＦ－β、Ｐａｘ３基因在心脏发育过程中的重要作用及细胞间的相互作用与心脏发育的关系，旨在揭示发育遗传与先天性心脏病的关联 。     

Molecules and Morphology,Phylogenetics and Genetics

Various explanations can be offered for the incongruence between phylogenetic hypotheses resulting from morphological and molecular data sets. Of these, the possibility that incongruence may result from the mutation of major morphogenetic genes leading to dramatic morphological divergence unaccompanied by equivalent change of the phylogenetic marker molecule(s) used is discussed in detail. As evidence for this hypothesis, several examples for such incongruence are surveyed. It seems possible that in many cases the genetic basis of the morphological characters responsible for the incongruence found may be simple, and that the genes involved may be homologous to genes known from mutant systems. It is suggested that: 1. the systematic documentation of incongruence between molecular and morphological phylogenies may help to assess the frequency of evolutionary change through the mutation of major morphogenetic genes, and that 2. the identification of major morphological characters distinguishing closely related taxa with mutant phenotypes known from mutant systems eventually may allow an experimental approach to the problem of evolutionary change resulting from major genes. Natural taxa suspected to be the result of such processes could be changed morphologically through transformation with the relevant genes.     

Molecules, Developmental Modules, and Phenotypes: A Combinatorial Approach to Homology

Most traditional views of homology rely on two unwarranted premises: the pervasively hierarchical nature of biology, inclusive of the levels of genes, development, and morphology and the linear mapping of genes onto developmental schedules and of developmental schedules onto phenotypes. These premises are only occasionally verified. Hierarchical behavior is negated by gene duplication and exon shuffling at the level of genes, by the coexistence of autonomous vs nonautonomous gene expression at the level of development, by ontogenetic repatterning at the level of morphology. The linearity of mapping of genes onto development is disturbed by genetic piracy, uncoupling of positional vs spatial control, and pleiotropy. The independence of developmental modules affects the mapping of development onto morphology and, finally, the peculiar topology of the epigenetic code affects the linearity of the gene to phenotype mapping. To cope with this complex behavior, a combinatorial approach to homology is recommended.     

Molecules, Morphology, Fossils, and the Relationship of Angiosperms and Gnetales

Morphological analyses of seed plant phylogeny agree that Gnetales are the closest living relatives of angiosperms, but some studies indicate that both groups are monophyletic, while others indicate that angiosperms are nested within Gnetales. Molecular analyses of several genes agree that both groups are monophyletic, but differ on whether they are related. Conflicts among morphological trees depend on the interpretation of certain characters; when these are analyzed critically, both groups are found to be monophyletic. Conflicts among molecular trees may reflect the rapid Paleozoic radiation of seed plant lines, aggravated by the long branches leading to extant taxa. Trees in which angiosperms are not related to Gnetales conflict more with the stratigraphic record. Even if molecular data resolve the relationships among living seed plant groups, understanding of the origin of angiosperm organs will require integration of fossil taxa, necessarily using morphology.     

Morphology and Homology of the Chiropteran Calcar, with Comments on the Phylogenetic Relationships of Archaeopteropus

Most researchers have considered the calcar to be a unique and homologous structure within Chiroptera (e.g., the presence of this structure and its associated musculature has been cited as a synapomorphy supporting bat monophyly). However, we report that significant morphological variation exists between Microchiroptera and Megachiroptera. In microchiropterans, a calcified or cartilaginous element articulates directly with the calcaneal tuberosity of the ankle and projects into the uropatagium. In megachiropterans, a cartilaginous structure projects from the tendon of the gastrocnemius muscle into the uropatagium and has no articulation with the calcaneal tuberosity. Considerable variation also exists in the musculature associated with these structures. Phylogenetic interpretation of hindlimb morphology of extant and fossil taxa indicates that the calcar may not be homologous in all bats. We suggest retention of the term calcar for the microchiropteran structure and propose a new term, uropatagial spur, for the megachiropteran structure. The fossil bat Archaeopteropus transiens (Oligocene) has long been presumed to be a megachiropteran; however, this form has a microchiropteran-type calcar. Reconsideration of morphological evidence from this and previous studies indicates that Archaeopteropus is not a megachiropteran but, rather, a basal member of the microchiropteran lineage.     

Evolution of Starfishes: Morphology, Molecules, Development, and Paleobiology. Introduction to the Symposium

Among starfishes, fascinating life cycles and complex morphologicalpatterns have evolved within a familiar but unusual basic bodyplan. In spite of these rich complexities, available phylogeneticinterpretations conflict, and the history of this importantgroup remains uncertain. The symposium brought together currentperspectives on phylogeny, the implications of certain poorlyknown aspects of asteroid morphology, and consideration of significantevents that preceded the diversification of extant asteroidgroups in the Mesozoic. It has become axiomatic in modern organismal biology that stronglysupported phylogenetic reconstructions are crucial to the understandingof biological pattern and progress. Although asteroids exhibitcomplex morphologies, life cycles, and behaviors that indicatetheir status as ideal model organisms in the study of marineinvertebrates, their evolutionary history remains obscure. Thisis in part due to a lack of treatment by researchers but alsoin part due to inherent limitations of the available data. In the following pages, the state of inquiry into the studyof relationships among starfishes is arranged in three sections:the nature of the fossil record (an introduction to modern starfishes),taxa and morphology, and phylogenetic interpretations.     

Morphology,Molecules, and Monogenean Parasites: An Example of an Integrative Approach to Cichlid Biodiversity

The unparalleled biodiversity of Lake Tanganyika (Africa) has fascinated biologists for over a century; its unique cichlid communities are a preferred model for evolutionary research. Although species delineation is, in most cases, relatively straightforward, higher-order classifications were shown not to agree with monophyletic groups. Here, traditional morphological methods meet their limitations. A typical example are the tropheine cichlids currently belonging to Simochromis and Pseudosimochromis. The affiliations of these widespread and abundant cichlids are poorly understood. Molecular work suggested that genus and species boundaries should be revised. Moreover, previous morphological results indicated that intraspecific variation should be considered to delineate species in Lake Tanganyika cichlids. We review the genera Simochromis and Pseudosimochromis using an integrative approach. Besides a morphometric study and a barcoding approach, monogenean Cichlidogyrus (Platyhelminthes: Ancyrocephalidae) gill parasites, often highly species-specific, are used as complementary markers. Six new species are described. Cichlidogyrus raeymaekersi sp. nov., C. muterezii sp. nov. and C. banyankimbonai sp. nov. infect S. diagramma. Cichlidogyrus georgesmertensi sp. nov. was found on S. babaulti and S. pleurospilus, C. franswittei sp. nov. on both S. marginatus and P. curvifrons and C. frankwillemsi sp. nov. only on P. curvifrons. As relatedness between Cichlidogyrus species usually reflects relatedness between hosts, we considered Simochromis monotypic because the three Cichlidogyrus species found on S. diagramma belonged to a different morphotype than those found on the other Simochromis. The transfer of S. babaulti, S. marginatus, S. pleurospilus and S. margaretae to Pseudosimochromis was justified by the similarity of their Cichlidogyrus fauna and the intermediate morphology of S. margaretae. Finally parasite data also supported the synonymy between S. pleurospilus and S. babaulti, a species that contains a large amount of geographical morphological variation.