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1.
两栖动物的不同科或属,乃至同一物种不同的地理种群内具有两种不同的性别决定系统,这种系统发生分布特征显示两栖动物的性别决定系统经历了多次转换。同型性染色体在许多两栖动物中存在,"高频转换"假说和"fountain-of-youth"假说是其形成的两种可能机制。激素在两栖动物性别决定早期起着重要作用。此外,我们还重点介绍了两栖动物中迄今唯一确认的性别决定基因(DM-W基因)。该综述将增进对两栖动物性别决定机制的多样性及其起源的认识,并为濒危两栖动物的物种保护和种群恢复以及养殖群体的利用提供科学依据。  相似文献   

2.
人的性别究竟是由什么来决定?过去人们常认为:人的性别由性染色体决定,且主要由Y染色体所决定,即在人体的体细胞内,除了含有成对的常染色体以外,凡含有x和Y染色体的为男性,凡含有两个x染色体的为女性。但是也有性染色体组成为XX的男性。据估计,具有XX性染色体的男性约在两万个男性中就有一个。为什么体细胞含有XX染色体的个体是男  相似文献   

3.
楚张卿  罗玮  夏云 《四川动物》2022,(4):462-472
性染色体进化及性别决定机制是脊椎动物进化研究的热点,近些年更是提出了性别组学的概念。脊椎动物各类群的性别决定机制呈现出多种形式,尤其是具有年青性染色体系统的类群的演化模式更为多样。由于年青性染色体在核型形态上差异不大,传统的研究方法难以识别,因此本文从细胞遗传学方法、性染色体上的DNA序列/RNA序列及其表达、蛋白质表达等多个维度阐述了年青性染色体和性别决定系统的鉴定方法。在高通量测序技术的基础上结合基因组学、蛋白质组学和代谢组学对性别决定系统进行更深层次的研究,从而形成性别组学,并最终解答性别决定的方式多样性及其背后的进化动力和分子途径。  相似文献   

4.
彭丹  武志强 《生物多样性》2022,30(3):21416-2886
植物中雌雄性别分化是一种进化的性状。雌雄异株在多个开花植物谱系中独立演化, 但各个支系的性染色体状态、性别决定区域与性别决定基因不尽相同。多样的植物性染色体和性别决定系统为研究植物性别相关基因的形成机制、性别决定区域和性染色体进化提供了极好的机会。随着测序技术的进步和分析方法的提高, 近年来越来越多物种性别决定的相关分子机制得到解析, 并将理论成果应用于提升经济效益与城市环境等实际问题中。本文将从目前的研究现状和方法, 性别决定单、双基因模型的建立, 植物性染色体进化过程等方面进行总结, 对未来植物性别决定的研究提出四点建议: (1)研究方向逐步从基因研究扩展到调控途径研究; (2)从单一物种转向相关科属比较研究; (3)改进现有性别决定基因模型或探索新模型和性别模式物种; (4)加强性别鉴定技术在实际生产中的研发工作。同时探讨性别决定理论研究未来在农业生产、园艺绿化种植中幼苗性别鉴别筛选等方面的应用前景。  相似文献   

5.
赵光强 《生物学通报》2002,37(12):19-21
高等植物的性别表型具多态性,这与植物性别决定的遗传基础有关,高等植的性别与性别决定基因,性染色体及常染色体有关,其性别决定系统有性别决定基因决定性别、性染色体决定性别及X染色体与常染色体间的基因平衡决定性别等多种方式。  相似文献   

6.
植物性别决定的研究进展   总被引:1,自引:0,他引:1  
陈书燕  安黎哲 《西北植物学报》2004,24(10):1959-1965
通过回顾近年来以多种植物为材料进行的性染色体观察,性别决定基因及调控方式的研究,对植物性别决定的机制进行了初步探讨,从而可以看出不同植物具有不同的性别决定机制:对于有性染色体的植物而言,目前已经从Y染色体上分离和鉴定了许多与雄性发育紧密相关的基因;部分性别决定基因和调控序列已利用构建减法文库,诱导突变体等方法从一些植物中获得。此外,还有研究表明,DNA脱甲基化,以及某些激素(如赤霉素、乙烯、Ace)都对植物的性别决定有重要作用。  相似文献   

7.
XY性染色体决定系统是决定植物性别的主要方式,但是对于其起源与演化机制却知之甚少。目前认为,携带控制雌蕊或雄蕊发育基因的一对常染色体由于某种未知原因的突变形成早期的neo-Y或neo-X性染色体,随着演化的进行,早期XY性染色体之间的重组逐渐受到抑制,非重组区域扩展最终形成异型的性染色体。研究发现,重复序列的累积以及DNA甲基化等因素都可能参与了XY性染色体的异染色质化、重组抑制及Y染色体体积增大过程。转座子作为一种基因组中含量最高的重复序列在性染色体演化中扮演了重要的角色,包括性染色体演化的起始激发,以及导致性染色体局部表观遗传修饰使其发生异染色质化扩展和重组抑制。文章综述了转座子在植物性染色体上的累积及其与性染色体异染色质化之间的关系,并简要分析了转座子在性染色体演化过程中的作用。  相似文献   

8.
早期胚胎的发育选择:性别决定   总被引:2,自引:0,他引:2  
程汉华  周荣家 《遗传》2007,29(2):145-149
性别决定是一个复杂的发育调控过程, 早期胚胎发育过程中, 雌雄二者必居其一的发育选择是胚胎性腺形成必须的发育决定。文章综述了动物性别决定的遗传系统、性腺发生、性别决定关键基因及其作用机制, 从分子进化的角度分析了性染色体与性别决定形成机制, 提示性别决定基因在进化中总是趋向异配性染色体。  相似文献   

9.
哺乳动物的性别决定包括初级性别决定和次级性别决定,是以SRY基因为主导,其他多个基因参与的级联调控过程。近年的研究表明。SRY、DAX1、SOX3等性染色体基因和SOX9、MIS、WT1、SF1等常染色体基因都参与性别决定的级联过程。结合中学生物学教材及发育生物学相关原理,从性染色体上和常染色体上与性别决定有关的基因阐述哺乳动物的性别决定机制,并简述了哺乳动物的性别决定模型。  相似文献   

10.
植物性染色体进化及性别决定基因研究进展   总被引:1,自引:0,他引:1  
秦力  陈景丽  潘长田  叶蕾  卢钢 《植物学报》2016,51(6):841-848
植物性染色体起源于1对常染色体,其在不同雌雄异株植物中多次起源并独立演变,是研究性染色体起源和进化机制的理想材料。过去的研究在一定程度上阐明了植物性染色体的起源和演化动力;且性染色体遗传退化、性别决定基因以及剂量补偿效应正逐渐成为研究的热点。近年来,关于植物性染色体进化及性别决定基因的研究取得了一些重要进展。该文综述了植物性染色体的起源、进化、遗传退化、剂量补偿效应以及性别决定基因等,并对植物性染色体进化研究发展趋势进行了展望。  相似文献   

11.
Sex Determination by Sex Chromosomes in Dioecious Plants   总被引:5,自引:0,他引:5  
Abstract: Sex chromosomes have been reported in several dioecious plants. The most general system of sex determination with sex chromosomes is the XY system, in which males are the heterogametic sex and females are homogametic. Genetic systems in sex determination are divided into two classes including an X chromosome counting system and an active Y chromosome system. Dioecious plants have unisexual flowers, which have stamens or pistils. The development of unisexual flowers is caused by the suppression of opposite sex primordia. The expression of floral organ identity genes is different between male and female flower primordia. However, these floral organ identity genes show no evidence of sex chromosome linkage. The Y chromosome of Rumex acetosa contains Y chromosome-specific repetitive sequences, whereas the Y chromosome of Silene latifolia has not accumulated chromosome-specific repetitive sequences. The different degree of Y chromosome degeneration may reflect on evolutionary time since the origination of dioecy. The Y chromosome of S. latifolia functions in suppression of female development and initiation and completion of anther development. Analyses of mutants suggested that female suppressor and stamen promoter genes are localized on the Y chromosome. Recently, some sex chromosome-linked genes were isolated from flower buds of S. latifolia.  相似文献   

12.
13.
In many species of animals, one of the sexes has a chromosome that is structurally and functionally different from its socalled homologue. Conventionally, it is called Y chromosome or W chromosome depending on whether it is present in males or females respectively. The corresponding homologous chromosomes are called X and Z chromosomes. The dimorphic sex chromosomes are believed to have originated from undifferentiated autosomes. In extant species it is difficult to envisage the changes that have occurred in the evolution of dimorphic sex chromosomes. In our laboratory, interracial hybridization between twoDrosophila chromosomal races has resulted in the evolution of a novel race, which we have called Cytorace 1. Here we record that in the genome of Cytorace 1 one of the autosomes of its parents is inherited in a manner similar to that of a classical Y chromosome. Thus this unique Cytorace 1 has the youngest neo-Y sex chromosome (5000 days old; about 300 generations) and it can serve as a ‘window’ for following the transition of an autosome to a Y sex chromosome.  相似文献   

14.
Most flowering plant species are hermaphroditic, but a small number of species in most plant families are unisexual (i.e., an individ-ual will produce only male or female gametes). Because species with unisexual flowers have evolved repeatedly from hermaphroditic progenitors, the mechanisms controlling sex determination in flowering plants are extremely diverse. Sex is most strongly determined by genotype in all species but the mechanisms range from a single controlling locus to sex chromosomes bearing several linked locirequired for sex determination. Plant hormones also influence sex expression with variable effects from species to species. Here, we review the genetic control of sex determination from a number of plant species to illustrate the variety of extant mechanisms. We emphasize species that are now used as models to investigate the molecular biology of sex determination. We also present our own investigations of the structure of plant sex chromosomes of white campion (Silene latifolia - Melan-drium album). The cytogenetic basis of sex determination in white campion is similar to mammals in that it has a male-specific Y-chromosome that carries dominant male determining genes. If one copy of this chromosome is in the genome, the plant is male. Otherwise it is female. Like mammalian Y-chromosomes, the white campion Y-chromosome is rich in repetitive DNA. We isolated repetitive sequences from microdissected Y-chromosomes of white campion to study the distribution of homologous repeated sequences on the Y-chromosome and the other chromosomes. We found the Y to be especially rich in repetitive sequences that were generally dispersed over all the white campion chromosomes. Despite its repetitive character, the Y-chromosome is mainly euchromatic. This may be due to the relatively recent evolution of the white campion sex chromosomes compared to the sex chromosomes of animals. © 1994 Wiley-Liss, Inc.  相似文献   

15.
Among the variety of breeding systems developed by flowering plants, those based on heteromorphic sex chromosomes are the most intellectually challenging in evolutionary terms. This is because, among other things, they enable us to compare sex determination processes between plants and animals. White campion (Silene latifolia, also named Lychnis or Melandrium) is dioecious and, much like us, females are homogametic (XX) and males are heterogametic (XY). Sexual dimorphism in white campion is controlled by two independent developmental pathways operating from the Y chromosome at very early developmental stages and within distinct regions of the flower. In addition, all basic steps in the evolution from the bisexual to the dioecious condition with heteromorphic sex chromosomes are known and available to experimentation in the genus Silene. This group of species has been under scrutiny for more than a century. Such an ideal experimental system enables us to tackle, with novel methodological tools, several classical questions in biology. These include the question of how sexual dimorphism evolved and how dimorphic development is controlled, as well as questions of how sex chromosomes evolve in the absence of meiotic recombination or how male-female genetic conflicts are generated. At the turn of the century, the time is now ripe to have a closer look. Received: 21 September 1999 / Accepted: 11 October 1999  相似文献   

16.
Heteromorphic sex chromosomes are common in eukaryotes and largely ubiquitous in birds and mammals. The largest number of multiple sex chromosomes in vertebrates known today is found in the monotreme platypus (Ornithorhynchus anatinus, 2n?=?52) which exhibits precisely 10 sex chromosomes. Interestingly, fish, amphibians, and reptiles have sex determination mechanisms that do or do not involve morphologically differentiated sex chromosomes. Relatively few amphibian species carry heteromorphic sex chromosomes, and when present, they are frequently represented by only one pair, either XX:XY or ZZ:ZW types. Here, in contrast, with several evidences, from classical and molecular cytogenetic analyses, we found 12 sex chromosomes in a Brazilian population of the smoky jungle frog, designated as Leptodactylus pentadactylus Laurenti, 1768 (Leptodactylinae), which has a karyotype with 2n?=?22 chromosomes. Males exhibited an astonishing stable ring-shaped meiotic chain composed of six X and six Y chromosomes. The number of sex chromosomes is larger than the number of autosomes found, and these data represent the largest number of multiple sex chromosomes ever found among vertebrate species. Additionally, sequence and karyotype variation data suggest that this species may represent a complex of species, in which the chromosomal rearrangements may possibly have played an important role in the evolution process.  相似文献   

17.
《遗传学报》2022,49(2):109-119
Many paleognaths (ratites and tinamous) have a pair of homomorphic ZW sex chromosomes in contrast to the highly differentiated sex chromosomes of most other birds. To understand the evolutionary causes for the different tempos of sex chromosome evolution, we produced female genomes of 12 paleognathous species and reconstructed the phylogeny and the evolutionary history of paleognathous sex chromosomes. We uncovered that Palaeognathae sex chromosomes had undergone stepwise recombination suppression and formed a pattern of “evolutionary strata”. Nine of the 15 studied species' sex chromosomes have maintained homologous recombination in their long pseudoautosomal regions extending more than half of the entire chromosome length. We found that in the older strata, the W chromosome suffered more serious functional gene loss. Their homologous Z-linked regions, compared with other genomic regions, have produced an excess of species-specific autosomal duplicated genes that evolved female-specific expression, in contrast to their broadly expressed progenitors. We speculate such “defeminization” of Z chromosome with underrepresentation of female-biased genes and slow divergence of sex chromosomes of paleognaths might be related to their distinctive mode of sexual selection targeting females rather than males, which evolved in their common ancestors.  相似文献   

18.
19.
As a result of suppressed recombination, heterogametic sex chromosomes (either Y or W) are usually assumed to gradually shorten over evolutionary time as a way to remove accumulated mutations. However, suppressed recombination removes the most obvious mechanism for excising portions of sex chromosomes. We examined ratios of W/Z chromosome size across 224 bird species from 146 genera. Much of the data were obtained from a previous study (Rutkowska et al. 2012. Biology Letters 8 : 636–638), who, similar to ourselves, found no gradual decrease in W chromosome length over evolutionary time. However, we show an abrupt decrease in W chromosome length at or just after the phylogenetic split between the two extant bird superorders, Paleognathae and Neognathae, indicating that the key to understanding sex chromosome evolution may have little to do with gradual suppression of recombination.  相似文献   

20.
横断山区四种湍蛙的细胞遗传学研究   总被引:5,自引:1,他引:4  
通过染色体组型分析,C带(BSG技术)分析及一种简便的Ag-NORs带分析,对四川湍蛙、理县湍蛙、棕点湍蛙和棘皮湍蛙的种间关系、染色体的演化及其性染色体等问题进行了初步探讨。结果表明:(1)四川湍蛙、理县湍蛙和棕点湍蛙之间的亲缘关系较近,而它们与棘皮湍蛙的亲缘关系较远;(2)在近缘种的分化中,染色体结构异染色质的变化和臂间倒位是重要的因素之一,这在小型染色体上表现得尤为突出;(三)四川湍蛙具有在形态上分化很明显的性染色体。C带分析表明,此性染色体主要由常染色质构成,但在其Y染色体的长臂上存在明显的中间C带,推测尚处于性染色体分化的初期阶段。  相似文献   

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