动物性别控制的途径和原理

动物性别控制在畜牧、养殖业中都具重要的经济价值,是发展生产和提高经济效益中重要的生物学环节。本文就目前用于动物性别控制的一些方法和原理作一简要的概述。控制个体发育的条件动物的表型性别可以由改变个体发育条件加以控制。 1.控制发育的温度鳄鱼后代的性别完全由胚胎发育的温度所决定。鳄鱼没有异形的性染色体,受精卵在30℃下,发育起来的全是雌性;在34℃以上,孵化出来的却是雄性;     

生殖激素对小鼠胚胎性别影响的研究(简报)

性别控制是人类很早就关心的研究领域,因为许多重要的经济性状与性别有直接关系。在家畜生产中,性别控制应用潜力很大,可以大幅度提高生产力,节约生产成本。性别控制可使肉用家畜多产雄性后代,乳用家畜多产雌性后代。为了达到控制     

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…     

部分水产养殖动物性别控制基因的研究进展

动物的性别是受遗传或环境等因素控制的。自从在哺乳动物中发现了性别决定基因SRY后,还发现了许多其他与性别控制和性腺发育相关的基因。由于海水养殖动物的性别控制技术在遗传育种和生产中十分重要,因此利用现代分子生物技术研究性别控制的基因成为热点。本文综述了鱼类、锯缘青蟹、海龟和海胆等水产养殖动物性别控制基因的研究进展。     

鱼类性别异形和性别决定的遗传基础及其生物技术操控

鱼类养殖对世界食品特别是动物蛋白的持续供给做出了至关重要的贡献.鱼类生殖对策的多样性,特别是单性雌核生殖方式的利用已开创了鱼类遗传育种的典型范例.不少鱼类在生长和个体大小等重要经济性状上表现出显著的性别异形.性别特异分子标记的开发和性别控制生物技术的发展为增加鱼产量及其经济价值提供了重要的技术途径.随着基因组学和分子遗传学技术的迅速发展,鱼类性别异形的遗传基础逐步被揭示,鱼类性别决定机制及其性别决定相关基因的鉴定已经取得了重大进展.本文对此进行了概述,以期为该领域的深入研究提供一些方向性和目标性思考.     

受精环境对哺乳动物性别形成的影响

性别控制是人类很早就关心的研究领域, 许多重要的经济性状与性别有直接的关系。控制受精环境即可控制性别, 这种方法不需昂贵的仪器设备或者药品, 易实践, 可普遍应用, 其经济效益和社会效益难以估量。文章综述了受精环境对哺乳动物性别形成影响的研究进展。这些环境因素包括母体生殖道中精氨酸含量、胚胎发育过程中子宫内葡萄糖浓度、输精时卵母细胞成熟程度以及哺乳动物受孕时生殖激素的水平等方面, 为进一步开展性别控制研究积累一定的资料。     

性别决定的研究进展

性别决定和性别分化是最基本的发育事件之一,也是生殖生物学研究的重要领域之一。性别决定是一个复杂的发育调控并涉及了进化时空的多基因多因素多层次的级联网络体系共同决定的活动过程。对性别决定的研究涉及遗传、发育与进化等学科的交叉研究领域,是生命科学中遗传一发育一进化主线条研究的极好模式。该领域的研究对生命活动规律等理论问题的认识具有借鉴和指导意义,并有助于认识性别决定机制。同时,性别决定的研究不仅有助于对动物性别的人为控制,而且利于人类性别分化异常的研究,包括分析病因、寻找可行性治疗方案。     

动物性别决定基因及其同源性比较

有性繁殖是动物繁衍后代的主要方式,关于这一机制的分子生物学研究已经有了相当的进展。在对模式动物线虫、果蝇以及人类自身的性别决定机制的研究中,几个关键的基因已经被克隆,其分子特征和作用机制也得到详细的阐述。通过对性别决定基因的比较发现,在性别决定过程中其下游调节因子较上游更为保守,在进化途径中出现较早。现就近几年动物性别决定进化途径的研究进展进行综述。     

控制动物性别的原理及方法

一、性别控制的基本原理控制动物性别的原理主要是基于动物雌雄生殖细胞,特别是动物精子的差异而讲行的。高等动物的X 型精子与 Y 型精子不论在形态结构、重量密度、表面膜电荷的电量分布及电性,还是精子的抗原免疫性、运动速度和活力以及耐酸碱性等方面都存在较大的差异。(一)精子形态结构的差异哺乳动物分裂中期细胞的性染色体,一般 X 比 Y 要大。如牛的 X 染色体表面积为7.85微米~2,Y 染色体为3.47微米~2,性染色体大小的差异造成了精子形态的差异。X 精子头部大而且比较圆,体和核也较大;Y 精子头部小而且比较尖,体和核比较小。此外,精子的大小还受     

哺乳动物性别控制的理论与实践

控制动物性别是人们早已渴望实现的目标,这对畜牧业具有特别重要的意义。一方面它可使人们更有效地进行肉奶生产,另一方面可缩短遗传改良的时间。长期以来,众多的科学家都在为之进行不懈地努力,在大量实验的基础上,对哺乳动物性别决定问题认识逐步深入。而该领域的每一次认识突破都导致人们去尝试新的性别控制方法。     

Improving the reliability of molecular sexing of birds using a W-specific marker

Molecular techniques for identifying sex of birds utilize length differences between CHD-Z and CHD-W introns, but in some cases these methods can lead to sexing errors. Here we show that an additional W-specific primer can be used in conjunction with a pre-existing sexing primer pair to dramatically improve the reliability of molecular sexing methods. We illustrate the approach with American coots (Fulica americana), a species with CHD-Z polymorphism that could not be accurately sexed using traditional methods. We developed a reverse primer GWR2 designed to sit within the intron of the W chromosome and amplify a distinctively small DNA fragment that serves as a W-specific marker. Analysis of known-sex individuals indicates that this W-specific primer provides an efficient and reliable protocol to identify the sex of F. americana. The development of such sex-specific primers will likely increase the reliability of molecular sexing methods in other birds as well. Comparisons between CHD-Z alleles of coots and common moorhens (Gallinula chloropus) revealed that CHD-Z polymorphism evolved separately in these two closely related species. We discuss the implications of repeated evolution of CHD-Z polymorphisms among birds.     

A PCR assay for gender assignment in dugong (Dugong dugon) and West Indian manatee (Trichechus manatus)

Gender assignment for some aquatic mammals in the field is difficult. Molecular sexing from tissue biopsies is possible as males are heterogametic. Here we describe a multiplex PCR assay that amplifies the male specific SRY gene and differentiates ZFX and ZFY gametologues in two sirenian species, dugong (Dugong dugon) and West Indian manatee (Trichechus manatus). The assay was validated with animals of known gender and proved accurate and robust to experimental failure.     

PCR-based sexing in conservation biology: Wrong answers from an accurate methodology?

Molecular tests of sex based on the polymerase chain reaction (PCR) are now commonplace in conservation biology, routinely guiding management decisions. While molecular approaches to sexing can be highly reliable, current practices may leave an undesirable level of uncertainty in the sexes identified, because researchers focus on determining the sex-specific nature of a test, largely ignoring the accuracy of the test to correctly sex individuals. This latter step requires considerably more known-sex individuals. We argue that, due to the well-known technical problems associated with PCR amplification, the demonstrated potential for sexing errors and few known-sex individuals being available from threatened species, conservationists should place greater emphasis on verifying the sexes identified with PCR tests. We propose that all individuals of the sex indistinguishable from an amplification failure (e.g., females in mammals XX, males in birds ZZ) should be verified with a second independent sex test. Such a consensus approach to molecular sexing would reduce errors that could arise due to technical failure and PCR anomalies, but may also reduce field and laboratory bookkeeping errors.     

Uncertainty in determination of sex from harvested bobcats

Considerable uncertainty often exists in estimates of demographic parameters based on data collected from harvested furbearer species. We used molecular genetic techniques to estimate rates of error in 2 methods of sex determination of harvested bobcats (Lynx rufus): manual examination of the carcass (field sex) and laboratory-based maximum canine root area (MRA sex). Error rates were high for both sexing techniques, and were associated with age and an age–sex interaction for the field and MRA sexing methods, respectively. These findings do not support the use of the field methods for identifying sex of harvested bobcats. The MRA method may be effective for determining sex of older bobcats but is limited by considerable overlap between sexes in juveniles and yearlings. If critical demographic parameters are estimated from harvest data, efforts should be made to identify and reduce rates of error before data are used to assess population status. © 2011 The Wildlife Society.     

A PCR-RFLP assay for gender assignment in the three-toed sloths (Bradypus, Pilosa, Bradypodidae)

The three-toed sloths (Bradypus) are slow-moving arboreal neotropical mammals. Understanding demographic variables (such as sex ratio) of populations is a key for conservation purposes. Nevertheless, gender assignment of Bradypus is particularly challenging because of the lack of sexual dimorphism in infants and in adults, particularly B. torquatus, the most endangered of the three-toed sloths, in which sex is attributed by visual observation of the reproductively active males. Here, we standardized a method for sexing Bradypus individuals using PCR-RFLP of sex-linked genes ZFX/ZFY. This assay was validated with known-gender animals and proved accurate to assign gender on three Bradypus species.     

Efficacy of a commercially available post-thaw bovine semen sexing kit in both single-ovulating and hyperstimulated cows

Currently, there are few inexpensive, reliable, effective methods for commercially separating X- and Y-chromosome bearing fresh and frozen bovine sperm. The objective of these experiments was to determine the efficacy of a commercially available post-thaw bovine semen sexing kit, HeiferPlus™ (HP) which claims to alter the sex ratio in favor of female calves following artificial insemination. Three trials included the insemination of hyperstimulated cows with Control or HP-treated semen, non-surgical embryo collection on Day 7, and a combined PCR/dot blot assay to determine embryo sex. Chi-square analysis showed that the Control group produced a greater proportion (p < 0.0005) of female embryos than the HP group. There were no differences in the proportions of transferable compared with degenerate embryos or in number of ovulations, embryos, and unfertilized ova collected from Control compared with HP groups. When treatments were combined, one of the two bulls used in the hyperstimulation studies produced an overall greater proportion of females (p < 0.05), suggesting a bull effect.Another trial involved the insemination of cows synchronized via OvSynch^® with fetal sexing via ultrasonography. Results of these studies indicated that HP semen sexing kit did not alter the sex ratio in favor of females in either hyperstimulated or single-ovulating cows; however, potential bull effects may be further evaluated to understand the capacity of HP with semen from specific bulls. Additionally, perhaps the sex of the surviving embryo can be manipulated by the maternal side, through ovarian, hormonal, oviductal, or uterine influences.     

Sex selection in mammals: a review

New methods for sperm separation and embryo sexing provide the opportunity to select the gender of the offspring of domestic mammals. We review here procedures currently available for pre- and post-fertilization sex determination, including flow cytometric selection of X- and Y-chromosome bearing spermatozoa and the application of the polymerase chain reaction to biopsied embryos. Modern techniques are considered in the context of the development of the field and parallel innovations in human medicine are briefly considered.     

Effect of ejaculate, bull, and a double swim-up sperm processing method on sperm sex ratio

Offspring gender preselection has applications of considerable economic, health and ecological interest. In this study we analysed modifications of the percentages of spermatozoa bearing Y and X chromosomes when semen samples are submitted to a double swim-up technique as a possible method for producing embryos of known sex with in vitro fertilisation protocols. As an initial experiment to provide accurate evaluation of the method we determined the possible incidence of natural deviations in the primary sex ratio between bulls or ejaculates, analysing the percentage of Y-chromosome DNA bearing spermatozoa (%Y-CDBS) with a polymerase chain reaction (PCR) amplification of X- and Y-specific fragments. Ejaculates were tested by direct semiquantitative PCR sexing and by sexing blastocysts produced in vitro with these spermatozoa. Bulls and ejaculates did not have any effect on the %Y-CDBS or on the sex ratio of embryos produced in vitro using these ejaculates. However, our double swim-up sperm preparation method produced differences in %Y-CDBS in some of the sperm fractions, suggesting that there are intrinsic differences in capacitation of X- and Y-bearing spermatozoa that might be used to produce embryos of the desired sex with in vitro fertilisation.     

A comparison of plucked feathers versus blood samples as DNA sources for molecular sexing

ABSTRACT.   Feathers are increasingly collected as a nondestructive source of DNA for avian genetic research. Although feather samples are not optimal in some important ways than more robust blood or tissue samples, feather sampling requires less training for field workers, results in shorter handling times for the organism, generates no hazardous wastes, and requires simpler storage procedures. Along with these largely positive attributes comes a set of challenges, particularly the relatively low copy number of DNA present in feather samples. We compared the utility and reliability of feathers to the more traditional blood samples as sources of DNA for polymerase chain reaction (PCR)-based molecular sexing of Black-capped Chickadees ( Poecile atricapilla ). DNA from 102 individuals was extracted separately from both single rectrices and from blood samples, and the sex of each bird was then determined using standard PCR-based methods. We found complete agreement between sex determinations based on feather versus blood DNA extractions. Slight variations in lab protocols were necessary to obtain consistent results from these two DNA sources; and we briefly discuss other sources of error that could occur in feather-based molecular sexing studies. This controlled comparison of feather versus blood samples demonstrates that plucked rectrices provide a highly reliable source of DNA for molecular sexing of wild birds.