遗传和温度因素对鱼类性别分化相关基因表达及性别比例的影响

鱼类的性别决定机制较为复杂,是遗传和环境共同作用的结果,具有很大的可塑性。随着分子生物技术的不断更新,对鱼类性别决定及分化相关基因的鉴定和研究有了新的进展,环境因子如温度、光照、p H、低氧、水压等均能影响大多数鱼类的性别决定和分化过程。本研究中,阐述了鱼类遗传型性别决定(GSD)和温度依赖型性别决定(TSD)方式,并对TSD与遗传型性别加温度影响(GSD+TE)性别决定机制下,性别决定相关基因在雌雄异型中的表达及结合温度诱导性逆转进行概述,分析了温度对鱼类性别比例的影响,并提出今后应加强对性别决定基因的鉴定、解析和基因功能研究,为科学制定鱼类繁殖计划提供指导。     

Mammalian ZFY sequences exist in reptiles regardless of sex-determining mechanism

In some reptiles, egg incubation temperature determines whether the embryo hatches as male or female; in others, sex chromosomes determine sex. A cloned gene (ZFY) representing the putative testis-determining factor in mammals was hybridized to genomic DNA of reptiles with sex chromosomes and to DNA of reptiles with temperature-dependent sex determination. No sex differences in hybridization patterns were observed. Hybridization of ZFY to polyadenylated RNA indicates that reptilian versions of this gene are expressed in embryos of both sexes during the temperature-sensitive period. If these highly conserved sequences are important in reptilian sex determination, then temperature-dependent and genotypic sex determination may have a similar molecular basis. For reptiles with XX/XY or ZZ/ZW systems, the absence of sex differences in hybridization patterns raises the question of whether the ZFY sequences reside on their sex chromosomes.     

家禽的性别决定和分化

家禽中虽未发现象哺乳动物SRY基因的性别决定片段,但XhoI家族中特异片段的发现可能成为性别决定基因研究的基础,性别分化的基础是控制性激素转型的芳香化酶;伴性遗传和泄殖腔鉴别法仍然是性别鉴定的主要方法;利用激素诱导只能使雌转雄而不能使雄转为雌,且转变后仍能恢复原来的遗传性别性别决定与分化本质的发现是家禽性别控制研究的重要课题     

Microinjected DNA from the X chromosome affects sex determination in Caenorhabditis elegans

The signal for sex determination in the nematode Caenorhabditis elegans is the ratio of the number of X chromosomes to the number of sets of autosomes (X/A ratio). By previous genetic tests, elements that feminized chromosomal males appeared to be widespread on the X chromosome, but the nature of these elements was not determined. In experiments to define a feminizing element molecularly, cloned sequences were added to chromosomally male embryos by microinjection into the mother. Three different X-chromosome clones, including part of an actin gene, part of a myosin heavy chain gene, and all of two myosin light chain genes, feminize chromosomal males. Both somatic and germline aspects of sex determination are affected. In contrast, about 40 kilobases of nematode autosomal DNA, phage lambda DNA, and plasmid pBR322 DNA do not affect sex determination. A feminizing region was localized to a maximum of 131 base pairs within an intron of the X-linked actin gene; a part of the gene that does not have this region is not feminizing. The results suggest that short, discrete elements found associated with many X-linked genes may act as signals for sex determination in C. elegans.     

鱼类性别决定基因研究综述

根据现有文献资料,对近几年有关鱼类性别决定基因方面的研究动态和进展作一综述,并提出研究中尚待解决的问题,为今后利用现代分子生物技术来研究鱼类性别控制的方法提供参考依据。     

Constraints in the evolution of sex ratio adjustment

When the relative fitness of male and female offspring varies with environmental conditions, evolutionary theory predicts that parents should adjust the sex of their offspring accordingly. Qualitative and even quantitative support for this prediction is striking in some taxa but much less convincing in others. Explaining such variation across taxa in the fit of sex ratio theory remains a major challenge. We use meta-analysis to test the role of two constraints in the evolution of sex ratios. Based on analysis of sex ratio skews in birds and wasps, we show that (i) mechanisms of sex determination do not necessarily constrain the evolution of sex ratio adjustment, and (ii) parental ability to predict their offsprings' environment influences the evolution of sex ratio patterns across taxa. More generally, our results show that multiple constraints may determine the precision of adaptation.     

家禽性别控制研究进展

家禽性别控制研究包括性别决定,性别分化,性别鉴定,性别诱导和性别控制5个方面,家禽中虽未发现象哺乳动物SRY基因的性别决定片段,但XhoI家族中特异片段的发现可能成为性别决定基因研究的基础。性别分化的基础是控制性激素转型的芳香化酶;伴性遗传和泄殖腔鉴别法仍然是性别鉴定的主要方法;利用激素诱导只能使雌转雄而不能使雄转为雌,且转变后仍能恢复原来的遗传性别,性别决定与分化本质的发现是家禽性别控制研究的重要课题。     

The evolution of sex chromosomes

Structurally distinct sex chromosomes (X and Y) are the most familiar mode of genetic sex determination and have evolved independently in many different taxa. The evolutionary paths by which their characteristic properties may have evolved are reviewed. These properties include the failure of X and Y to recombine through much or all of their length, the genetic inertness of much of the Y chromosome, dosage compensation of the activity of X chromosomal loci, and the accumulation of repeated DNA sequences on the Y chromosome.     

禽类性别及性别控制的研究进展

禽类的性决定、性分化和性别控制方面的研究现状表明：禽类的性决定机制尚不十分清楚。除了公认的性染色体理论，还有常染色体／Ｚ染色体平衡理论的争论。但性别最终由基因决定，在禽类尚未发现象Ｙ染色体上的ＳＲＹ片段。作者提出了“Ｚ染色体上的性别基因可能以剂量效应来决定性别”的设想。禽类性别的有效控制将取决于对其性决定、性分化本质的了解。     

鱼类性别决定及其基因的研究进展

综述鱼类性别决定类型及其机制的研究动态和进展,旨在为系统研究鱼类性别决定机制提供参考。     

Analysis of the Offspring Sex Ratio of Chicken by Using Molecular Sexing

The overall sex ratio of offspring （dead embryos and hatch chicks） from all the fertilized eggs of 140 hens collected for 30 days was studied using duplex PCR of certain fragments of sex chromosomes. Additional 894 dead embryos over a period of 21 days of incubation were also investigated to verify the sex ratio of the dead embryos. The sex of the early dead embryos was identified using this molecular sexing technique. The sex ratio of the hatch chicks and the total offspring of the hens investigated in this experiment did not differ from the expected sex ratio （i.e., 1：1）., However, the number of female dead embryos was significantly more than that of males. The data indicated that the different physiologic function of males and females contributed to female-biased mortality during incubation. It was also found by further analysis that the sex ratios of the offspring of some hens were significantly biased to female or male over the period investigated, which suggested that the sex ratio of offspring might be influenced by the maternal condition to some degrees.     

Local mate competition and parental investment in social insects

Efforts to develop formulas for contrasting genetic interests of workers and queens in social Hymenoptera are complicated by many factors, including multiple matings by queens, oviposition by unmated females, and mating rivalry among genetic relatives (Hamilton's "local mate competition"). Because of haplodiploid sex determination in Hymenoptera, when such influences are absent, queens benefit from 1:1 sex ratios of investment (male: female) in reproductive offspring, workers from 1:3 ratios among reproductive siblings. Reports of variable ratios, including many well above 1:3, and female biases in nonsocial Hymenoptera and diplodiploid termites, implicate local mate competition and raises questions about previous interpretations that workers have their way.     

旱地植物蒸腾作用研究进展

从影响植物蒸腾的主要因素、植物蒸腾的生理调节、提高植物蒸腾效率的措施及植物蒸腾测试方法的改进等方面综述了旱地植物蒸腾作用研究的进展.     

Sex determination in the social amoeba Dictyostelium discoideum

The genetics of sex determination remain mysterious in many organisms, including some that are otherwise well studied. Here we report the discovery and analysis of the mating-type locus of the model organism Dictyostelium discoideum. Three forms of a single genetic locus specify this species' three mating types: two versions of the locus are entirely different in sequence, and the third resembles a composite of the other two. Single, unrelated genes are sufficient to determine two of the mating types, whereas homologs of both these genes are required in the composite type. The key genes encode polypeptides that possess no recognizable similarity to established protein families. Sex determination in the social amoebae thus appears to use regulators that are unrelated to any others currently known.     

RAPD分子标记在蜜蜂遗传育种中的应用

RAPD分子标记在蜜蜂遗传育种中得到较广泛应用 .利用 RAPD分子遗传标记 ,估测蜜蜂性别决定位点 (x)与低幼虫存活率位点的标记序列位置 (STS)之间的遗传距离为 1 .6c M;构建了蜜蜂 (Apismellifera)遗传连锁图 ,确定了蜜蜂性基因位点 (x)、黑色体色基因位点 (blk)、苹果酸脱氢酶 (Mdh-1 )位点分别位于第 3、6、1 8个连锁群 ;确定了影响蜜蜂采粉、报警信息素水平、螫刺行为和体长等数量性状的基因座位 ;筛选出 5种引物 ,这些引物所扩增的 RAPD标记可作为鉴别欧洲蜜蜂和非洲蜜蜂 (A. mellifera L.)的分子标记 .蜜蜂高产性状 RAPD标记的研究已取得一定进展     

用动物模型估计约克夏猪的主要经济性状遗传参数的研究

采用动物模型DFREML，进行了性别对约克夏猪主要经济性状遗传参数影响的研究。结果表明：约克夏猪的主要经济性状的最小二乘平均值在公母猪之间有明显的差异（P＜0．05）；模型中同时考虑母体效应时得到的遗传力均低于没有考虑母体效应时的遗传力。将性别作为国家效应时的各性状间的遗传相关高于只考虑公猪时的各性状间的遗传相关，但低于只考虑母猪时的各性状间的遗传相关。     

Temperature sex reversal implies sex gene dosage in a reptile

Sex in reptiles is determined by genes on sex chromosomes or by incubation temperature. Previously these two modes were thought to be distinct, yet we show that high incubation temperatures reverse genotypic males (ZZ) to phenotypic females in a lizard with ZZ and ZW sex chromosomes. Thus, the W chromosome is not necessary for female differentiation. Sex determination is probably via a dosage-sensitive male-determining gene on the Z chromosome that is inactivated by extreme temperatures. Our data invite a novel hypothesis for the evolution of temperature-dependent sex determination (TSD) and suggest that sex chromosomes may exist in many TSD reptiles.     

哺乳动物生殖细胞的性别决定

生殖细胞从未成熟阶段发育到成熟阶段有2个主要的细胞命运决定:进行减数分裂时间的决定和分化为精子还是卵子的决定,这2个决定是密切偶联的。主要阐述了哺乳动物生殖细胞性别决定的分子机制以及减数分裂在生殖细胞性别决定中的作用机制。