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.     

中国原鸡(Gallus gattus) 的染色体研究

 本文报道了产于中国南部原鸡(Gallus gallus)的染色体组型及其 G-带核型。其染色体数目2n=78;性染色体雄性为zz,雌性为 zw。全部常染色体(包括微小染色体)和性染色体经测量分析,计算了双臂染色体的臂比、着丝粒指数和全部染色体的相对长度。分析了1—19号常染色体和性染色体的G-带带型,并绘制了相对长度模式图和G-带模式图。     

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。     

Progress in studies of sex determination mechanisms and sex control techniques in Cynoglossus semilaevis (half-smooth tongue sole)

The Cynoglossus semilaevis (half-smooth tongue sole) is a marine flatfish of great commercial value for fisheries and aquaculture in China. It has a female heterogametic sex determination system (ZW/ZZ) and environmental factors can induce sex-reversal of females to phenotypic males, suggesting that it is a promising model for the study of sex determination mechanisms. Additionally, females grow much faster than males and it is feasible to improve the aquaculture production through sex control techniques. This paper reviews the progress in research on sex determination mechanisms research in our laboratory. We have completed whole-genome sequencing and revealed the genome organization and sex chromosome evolution of C. semilaevis. A putative male determining gene dmrt1 was identified and DNA methylation was verified as having a crucial role in the sex reversal process. Genetic maps and sex-specific biomarkers have been used in a marker-assisted selection breeding program and for differentiation of the fish sex. Development and improvement of sex control technologies, including artificial gynogenesis and production of breeding fry with high proportion of females, is also reviewed. These research advances have provided insight into the regulation of sex determination and enabled efficient sex management in artificial culturing of C. semilaevis.     

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.     

戴胜(Upupa epops)的染色体组型研究

 本文报道了戴胜(Upupa epops)的染色体组型研究结果。其染色体二倍体数2n=128。这是迄今已研究过的鸟类染色体二倍体数目最多的一种。在常染色体中,1—10号为双臂染色体(中、近中或近端着丝粒染色体);11—63号全为端部着丝粒染色体。雄性性染色体ZZ是整个染色体组中最长的一对近端着丝粒染色体;雌性的W染色体也为近端着丝粒染色体,其长度仅次于第3号常染色体。本研究结果为鸟类细胞分类学和研究鸟类的核型进化提供了新的细胞遗传学资料。     

雌雄异株植物性染色体演化研究进展

植物的性别分化是植物发育生物学的热点问题,而植物性染色体的研究有助于阐明性染色体起源和演化的机制,因此成为研究植物性别分化的重点领域。对模式种雌雄异株植物番木瓜、白麦瓶草和酸模性染色体研究进展以及性染色体演化进行了概述,以期为后续的研究奠定基础。     

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.     

珍珠鸡与家鸡的染色体核型比较分析

为了探索珍珠鸡染色体的细胞遗传学特征,以珍珠鸡和贵州黄家鸡为研究对象,采用骨髓法和外周血淋巴细胞培养法分别制备珍珠鸡和家鸡的染色体标本并对其染色体核型进行分析。结果表明:1)两种雄性鸡均为同型染色体(ZZ),Z染色体的相对长度为(9.31±0.50)%～(9.84±0.85)%,介于4号与5号染色体间,为中着丝粒染色体;两种雌性鸡均为异型染色体(ZW),Z染色体的大小、类型均与雄性鸡相同,珍珠鸡的W染色体相对长度较长,为(4.19±0.23)%,介于7号与8号染色体间,家鸡的W染色体相对长度为(4.12±0.23)%,介于8和9号染色体间,两者的W染色体均为中着丝粒。2)家鸡与珍珠鸡前10对染色体的相对长度差异不大,但染色体形态存在一定差异,主要集中在2号和5号染色体上,家鸡的2号和5号染色体为中着丝粒和端着丝粒,珍珠鸡对应的染色体分别为亚中着丝粒和中着丝粒,其余染色体的着丝粒位置相同。结论:属于珍珠鸡科的珍珠鸡与家鸡的染色体核型存在一定差异。     

建昌鸭、北京鸭与绿头鸭(Anas platyrhynchos)的核型及G带带型

本试验分析了两种家鸭(建昌鸭和北京鸭)和绿头鸭(Anas platyrhynchos的核型及G带带型。结果表明,三种鸭的核型相似。染色体数目2n=80(♂、♀)染色体基本臂数为86(♂)或85(♀)。性染色体为ZZ(♂)/ZW(♀)型。1号和2号染色体分别属亚中部(sm)和中部(m)着丝粒染色体。Z染色体(4号)属亚端部着丝粒染色体,具有明显的短臂。W染色体(大小相当于7-9号)和其余常染色体均属端着丝粒染色体。三种鸭的染色体G带带型显示出很大的同源性。本试验结果从核分类学角度说明了,在起源上家鸭与绿头鸭的亲缘关系密切,绿头鸭很可能是家鸭的祖先。     

番木瓜性别决定的研究进展

番木瓜具有3种性别类型,性别遗传机制较复杂.对番木瓜性别决定、性染色体、性别紧密连锁的DNA分子标记、基因组高密度遗传连锁图谱、性别决定位点物理图谱等方面进行了综述分析,指出研究番木瓜的性别遗传及性别表达机理在定向改良番木瓜的性别方面具有重要意义.     

The possibility of sex control by artificial insemination with centrifuged spermatozoa

The results of experiments carried out at the Wisconsin Agricultural Experiment Station to test the possibility of controlling sex by artificial insemination with centrifuged spermatozoa in rabbits and swine are presented. Microscopic studies of spermatozoa showed dimorphism in the head lengths but separation by centrifuging was not complete. According to the chromosome theory, if the ovum is fertilized by an X-bearing spermatozoon, the resulting individual will contain 2 X chromosomes in its cells and will be female. If the ovumn is fertilized by a Y-bearing chromoxome spermatozoon, the resulting individual will contain and X and a Y chromosome in its cells and be a male. The Y-containing spermatozoa are thought to have smaller heads than the X-containing ones. Centrifugal separation of male- and female-producing spermatozoa was attempted with liquid recovered by means of a catheter from the vagina and uterus of rabbits. Other rabbits were then artificially inseminated with portions of this liquid and sex of young produced was recorded. Many young were produced from centrifuged spermatozoa and many from spermatozoa exposed to low temperatures for periods up to 24 hours. Modification of sex ratios was not significant. This investigation failed to show a practical method of controlling sex ratios among the offspring of higher animals.     

Paucity of genes on the Drosophila X chromosome showing male-biased expression

Sex chromosomes are primary determinants of sexual dimorphism in many organisms. These chromosomes are thought to arise via the divergence of an ancestral autosome pair and are almost certainly influenced by differing selection in males and females. Exploring how sex chromosomes differ from autosomes is highly amenable to genomic analysis. We examined global gene expression in Drosophila melanogaster and report a dramatic underrepresentation of X-chromosome genes showing high relative expression in males. Using comparative genomics, we find that these same X-chromosome genes are exceptionally poorly conserved in the mosquito Anopheles gambiae. These data indicate that the X chromosome is a disfavored location for genes selectively expressed in males.     

Environmental sex determination: interaction of temperature and genotype in a fish

Sex determination in an atherinid fish, the Atlantic silverside (Menidia menidia), is under the control of both genotype and temperature during a specific period of larval development. The sex ratios of the progeny of different females are variable and differ in their responsiveness to temperature. This demonstrates that sex ratio in fishes that normally have separate sexes can be influenced by the environment.     

Permanent translocation heterozygosity and sex determination in East african mistletoes

Viscum fischeri has 2n = 23 chromosomes in male plants. These fornm 7 bivalents and a translocation chain of 9 chromosomes during meiosis. Pollen with 11-and 12-chromosome genomes is thus produced. Female plants have 2n = 22 chromosomes and produce 11 bivalents during meiosis. Sex determination is technically a rare multiple X-multiple Y type, but more importantly it provides the mechanism whereby permanent translocation heterozygosity is maintained in the system. In a second species, Viscum engleri, male plants have 2n=28 chromosomes associating as 11 bivalents and a ring of 6 chomosomes at meiosis.     

四川麻鸭染色体组型分析

本试验分析了四川麻鸭(Anas platyrbynchos domestica)的染色组型。染色体数目2n=80(♂、♀)。染色体基本臂数为86(♂)或85(♀)。性染色体为ZZ(♂)/ZW(♀)型。1号和2号染色体分别属亚中部(sm)和中部(m)着丝粒染色体。Z染色体(4号)属亚端部(st)着丝粒染色体。W染色体(大小相当于8号)和其余常染色体均属端着丝粒(T)染色体。