性别决定基因

在个体发育过程中,动物的种类不同,性别决定的方式亦有差异。这取决于胚胎早期不同的性别初级信号对性别决定基因的启动和活化,活化的性别决定基因启动性别分化基因的表达,使个体的性别表现出来。本文略述与线虫、果蝇等的性别决定有关的基因。线虫(Caenorhabditis elegans)体长约1mm,雌雄同体,自体受精。有两条 X 染色体(XX);XO型线虫为雄性。线虫(C.elegans)性别决定的初级信号是 X 染色体与常染色体的比率(X∶     

木本植物性别决定基因研究进展

雌雄异株植物是研究性别决定遗传机制及性染色体起源与进化的理想材料,而克隆性别决定基因是解析性别决定遗传机制的关键。木本植物中有丰富的雌雄异株植物,且包括2种相反的性别决定系统：XY型(雌株为同配型的XX,雄株为异配型的XY)和ZW型(雌株为异配型的ZW,雄株为同配型的ZZ)。此外,不同性别植株的经济价值也有所不同。在木...     

一个新的性别决定基因DMY

虽然人们已经鉴定出了线虫、果蝇和哺乳动物的性别决定基因,但直到最近才首次在非哺乳类脊椎动物中发现了性别决定基因DMY.介绍了在青鳉中发现DMY基因的经过,发现DMY基因的意义和DMY基因在其他鱼类中的分布,最后对未来的研究进行了展望.     

寻找人类性别决定基因的历程

动物和人类性别决定机制的探讨是生命科学中一个重要研究领域,性决定和性分化过程决定着雌性和雄性两种性别的存在。性别决定是在受精的瞬间就确定了的,是性分化的遗传基础;而性分化则是一个由早期胚胎至性成熟分化发育的复杂调控过程。该项研究不仅有益于对人类性别相关疾病的诊断治疗,而且对于动物性别的人为控制和个体性别鉴定,以及对于从低等脊椎动物到人类性别决定机制进化的探讨都具有重大价值。１　人类中存在性别决定基因对于哺乳动物的早期研究结果已使人们认识到精子有两种类型：“Ｘ精子”和“Ｙ精子”,受精时哪种类型的精…     

黄瓜性别决定相关基因和性别表达机制

介绍黄瓜的性别决定相关基因,黄瓜性别决定的假说和性别决定的分子机制的研究进展.     

SRY基因及其性别决定

对近十年来关于脊椎动物尤其是哺乳动物的SRY基因及其性别决定机制的研究进展作了简要的综述。扼要阐述了哺乳动物的SRY基因的结构、转录、表达及其在性别决定中的作用模式及相关的基因家族。     

性别决定基因SRY的研究进展

SRY基因是哺乳动物性别决定过程中的主宰基因,其表达产物SRY蛋白是一种DNA结合蛋白,该蛋白含有一个HMG盒,能够以序列特异性结合到DNA双螺旋链的一侧,起到转录因子的作用。调节或协同下游基因如SOX9、AMH等基因的表达,使胚胎发育向雄性方向发展。     

Genetics of sex determination in flowering plants

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.     

Environmental sex reversal,Trojan sex genes,and sex ratio adjustment: conditions and population consequences

The great diversity of sex determination mechanisms in animals and plants ranges from genetic sex determination (GSD, e.g. mammals, birds, and most dioecious plants) to environmental sex determination (ESD, e.g. many reptiles) and includes a mixture of both, for example when an individual’s genetically determined sex is environmentally reversed during ontogeny (ESR, environmental sex reversal, e.g. many fish and amphibia). ESD and ESR can lead to widely varying and unstable population sex ratios. Populations exposed to conditions such as endocrine‐active substances or temperature shifts may decline over time due to skewed sex ratios, a scenario that may become increasingly relevant with greater anthropogenic interference on watercourses. Continuous exposure of populations to factors causing ESR could lead to the extinction of genetic sex factors and may render a population dependent on the environmental factors that induce the sex change. However, ESR also presents opportunities for population management, especially if the Y or W chromosome is not, or not severely, degenerated. This seems to be the case in many amphibians and fish. Population growth or decline in such species can potentially be controlled through the introduction of so‐called Trojan sex genes carriers, individuals that possess sex chromosomes or genes opposite from what their phenotype predicts. Here, we review the conditions for ESR, its prevalence in natural populations, the resulting physiological and reproductive consequences, and how these may become instrumental for population management.     

Segregating variation for temperature-dependent sex determination in a lizard

Temperature-dependent sex determination (TSD) was first reported in 1966 in an African lizard. It has since been shown that TSD occurs in some fish, several lizards, tuataras, numerous turtles and all crocodilians. Extreme temperatures can also cause sex reversal in several amphibians and lizards with genotypic sex determination. Research in TSD species indicates that estrogen signaling is important for ovary development and that orthologs of mammalian genes have a function in gonad differentiation. Nevertheless, the mechanism that actually transduces temperature into a biological signal for ovary versus testis development is not known in any species. Classical genetics could be used to identify the loci underlying TSD, but only if there is segregating variation for TSD. Here, we use the ‘animal model'' to analyze inheritance of sexual phenotype in a 13-generation pedigree of captive leopard geckos, Eublepharis macularius, a TSD reptile. We directly show genetic variance and genotype-by-temperature interactions for sex determination. Additive genetic variation was significant at a temperature that produces a female-biased sex ratio (30 °C), but not at a temperature that produces a male-biased sex ratio (32.5 °C). Conversely, dominance variance was significant at the male-biased temperature (32.5 °C), but not at the female-biased temperature (30 °C). Non-genetic maternal effects on sex determination were negligible in comparison with additive genetic variance, dominance variance and the primary effect of temperature. These data show for the first time that there is segregating variation for TSD in a reptile and consequently that a quantitative trait locus analysis would be practicable for identifying the genes underlying TSD.     

Evidence of thermolabile sex determination in pejerrey*

Temperature regimes of 17 ± 1°C and 21 ±1°C early in development of pejerrey Odontesthes bonariensis produced nearly all females, whereas at 25 ± 1°C variable, sometimes male-biased sex-ratios were obtained. The critical period of thermolabile sex determination seemed to occur between 25 and 50 days post-hatch (about 11 and 21 mm s.i.) at low temperatures (17–20°C) and between 0 and 25 days (about 7 and 15 mm) at high temperatures (22–25°C). The likelihood of expression of temperature-dependent sex determination in natural populations and the possible adaptive significance of environmental sex determination in pejerrey are discussed.     

植物性别决定的研究进展

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。     

Exploring the evolution of environmental sex determination, especially in reptiles

Environmental sex determination has been documented in a variety of organisms for many decades and the adaptive significance of this unusual sex-determining mechanism has been clarified empirically in most cases. In contrast, temperature-dependent sex determination (TSD) in amniote vertebrates, first noted 40 years ago in a lizard, has defied a general satisfactory evolutionary explanation despite considerable research effort. After briefly reviewing relevant theory and prior empirical work, we draw attention to recent comparative analyses that illuminate the evolutionary history of TSD in amniote vertebrates and point to clear avenues for future research on this challenging topic. To that end, we then highlight the latest empirical findings in lizards and turtles, as well as promising experimental results from a model organism, that portend an exciting future of progress in finally elucidating the evolutionary cause(s) and significance of TSD.     

膜翅目昆虫的性别决定机制

昆虫性别决定机制存在多样性和复杂性,其中膜翅目昆虫的性别决定由单双倍体决定,单倍体为雄性,二倍体为雌性。本文就膜翅目昆虫的性别决定模式和分子机制进行综述。膜翅目昆虫性别决定有6种模式,即互补性性别决定(complementary sex determination, CSD)、多位点互补性性别决定(multiple-locus CSD, ml-CSD)、基因组印记、母体效应、内共生体诱导产雌单性生殖、父本遗传基因组消除(paternal genome elimination, PGE)。其中,CSD机制是目前在膜翅目昆虫中普遍接受的性别决定模式。而蜜蜂的CSD性别决定机制是膜翅目昆虫性别决定模式中的典型代表,受csd→fem→dsx这一调控级联的控制。     

遗传学史在遗传学教学中的作用

科学史的研究和发展状况能反映一个国家的科学技术水平,遗传学史是生命科学发展史的一个重要分支,21世纪是生命科学的世纪,在遗传学教学中加强遗传学发展史的介绍,不仅具有教育功能,使学生了解遗传学的产生和发展,而且可以培养学生的思维能力和科学素质。本文就遗传学史的教育功能及在教学中的作用进行论述。     

Evolutionary transitions between mechanisms of sex determination in vertebrates

Sex in many organisms is a dichotomous phenotype--individuals are either male or female. The molecular pathways underlying sex determination are governed by the genetic contribution of parents to the zygote, the environment in which the zygote develops or interaction of the two, depending on the species. Systems in which multiple interacting influences or a continuously varying influence (such as temperature) determines a dichotomous outcome have at least one threshold. We show that when sex is viewed as a threshold trait, evolution in that threshold can permit novel transitions between genotypic and temperature-dependent sex determination (TSD) and remarkably, between male (XX/XY) and female (ZZ/ZW) heterogamety. Transitions are possible without substantive genotypic innovation of novel sex-determining mutations or transpositions, so that the master sex gene and sex chromosome pair can be retained in ZW-XY transitions. We also show that evolution in the threshold can explain all observed patterns in vertebrate TSD, when coupled with evolution in embryonic survivorship limits.     

人类性别决定和性别分化研究进展

SRY基因在人类性别分化中起着关键作用,目前研究认为SRY仅是涉及性别决定过程的基因之一,其他基因和SRY相关基因SOX9,抗副中肾激素基因AMH,编码缁类因子的基因SF1,X－连锁的DAX基因,wilm‘s肿瘤抑制基因WT1等基因都参与了人类性腺分化和发育,本文拟就人类性别决定基因的研究进展及其与人类性别分化的关系作一综述。