用于果蝇唾腺染色体实验材料的培养方法

果蝇唾腺染色体观察是遗传学实验教学中的一个主要项目，培养适宜的果蝇用于其染色体观察对实验成败十分关键。文章从培养基的组成与制备，培养条件与培养过程，培养的果蝇唾腺染色体的特点等方面，对用于唾腺染色体观察的果蝇的培养作了详细介绍，以期促进果蝇唾腺染色体观察的实验教学。     

洋葱染色体G带和R带的研究

本文报道了洋葱(Allium cepe)根尖染色体G带和R带的研究结果。本试验采用秋水仙碱前处理,用纤维酶及果胶酶去壁,用蒸气干燥法制片,应用胰酶—尿素法进行显带。结果诱导出洋葱根尖细胞染色体的两种清晰的染色质带。因两种带纹着色深浅的部位正好相反,正如人类染色体显示的G带和R带,因此我们称之为洋葱染色体的G带和R带。洋葱染色体的G带和R带在同一分裂相中每条染色体均显示带纹,带纹分布于整条染色体上,与C带带纹显然不同。     

武汉地区3种果蝇的唾腺及唾腺染色体的比较研究

本文对武汉地区3种果蝇的幼虫、唾腺及唾腺染色体进行了比较研究,并对果蝇唾腺染色体的制片技术进行了一些改进。结果表明D.ummgrans果蝇是研究果蝇唾腺染色体的一种极好的材料。     

植物染色体C-带带型制作技术的改良

利用黄瓜新泰密刺种子根尖为材料,制作黄瓜中期染色体C显带制片,得到清晰稳定的染色体C显带带纹,在采用常规压片和去壁低渗的制片方法的基础上,对植物染色体显带的制片方法进行了改进。结果显示,利用改良后的方法得到了较多的且清晰稳定的黄瓜中期染色体C显带带纹,其单倍染色体带纹总数为30。结论:染色体制片中的解离、压片、干燥等多个步骤对染色体显带有显著的影响。     

多头绒泡菌线粒体中肌动蛋白的免疫细胞化学鉴定

自多头绒泡菌(Physarum polycephalum Schw.)原质团中分离线粒体,以兔抗肌动蛋白抗体为一抗,荧光素标记的羊抗兔IgG和辣根过氧化物酶标记的羊抗兔IgG作二抗进行间接免疫荧光和蛋白质免疫印迹实验.结果显示,线粒体中含有与肌动蛋白抗体呈阳性反应的抗原.以兔抗肌动蛋白抗体作一抗,金颗粒标记的蛋白A作二抗进行的间接免疫电子显微镜实验结果进一步证明了肌动蛋白是多头绒泡菌线粒体的组成成分,并在线粒体中呈散在分布.     

草绿异色蝗珠染色体C—带核型

报道了珍稀昆虫草绿异色ｍｅｒａｃｒｉｓ ｐｒａｓｉｎａ Ｎｉｕ ｅｔ Ｚｂｅｎｇ）的染色体Ｃ－带核型、该种蝗虫的型为２ｎ＝２２＋ＸＯ，全部染色体为端部着丝粒染色体，Ｃ带主要分布在着丝粒区，３号染色体具有端带，５号染色体Ｃ带带纹非常丰富。     

油松及云南松染色体的荧光带型

利用两种荧光试剂ＣＭＡ和ＤＡＰＩ研究油松及云南松染色体的荧光带型。油松（２ｎ＝２４）和云南松（２ｎ＝２４）染色体的ＣＭＡ带型中均存在五种不同的ＣＭＡ带纹类型。油松的ＣＭＡ带型为３对是着丝粒和臂间处均有荧光带纹的中部着丝粒染色体（Ａ类型）,３对是臂间处有荧光带纹的中部着丝粒染色体（Ｂ类型）,２对是着丝粒处有荧光带纹的中部着丝粒染色体（Ｃ类型）,２对是无荧光带纹的近中或中部着丝粒染色体（Ｄ类型）,２对是着丝粒有荧光带纹的近中着丝粒染色体（Ｅ类型）;而云南松的ＣＭＡ带型则为Ａ类型、Ｂ类型、Ｃ类型、Ｄ类型和Ｅ类型的染色体分别有４对、２对、２对、２．５对和１．５对。这两种松树染色体的ＤＡＰＩ荧光带型与ＣＭＡ带型之间存在相反的带纹关系。最后讨论认为①利用荧光带型的不同可将二者区分开,②据荧光带型认为云南松在赤松亚组中与其它松树之间的亲缘关系可能要远一些。     

草绿异色蝗的染色体C-带核型

报道了珍稀昆虫草绿异色蝗ＤｉｍｅｒａｃｒｉｓｐｒａｓｉｎａＮｉｕｅｔＺｈｅｎｇ）的染色体Ｃ－带核型．该种蝗虫（副模１）的核型为２ｎ＝２２＋ＸＯ，，全部染色体为端部着丝粒染色体，Ｃ带主要分布在着丝粒区，３号染色体具有端带，５号染色体Ｃ带带纹非常丰富     

药百合根尖染色体C带分析

利用Giemsa C带方法对药百合(Lilium speciosum Thunb. var. glorosoides Baker)进行了研究。结果表明：药百合的染色体数目为2n=2x=24,带型公式为：2n=24=8C+4CI++2CI++2CN+4I++2I+T++2,单套染色体条带总数为20条。染色体A、E、H、J、K的着丝点区域和染色体F的短臂上显示出很强的带纹,染色体 A为随体染色体,具有明显的次缢痕带,染色体B的短臂上显示出3条强弱不同的带纹。通过Giemsa C带方法可以将药百合的每条染色体区分开,药百合C带带纹的这些特征将为其在杂交育种中后代的鉴定及特异基因的染色体定位提供可靠的依据。     

马尾松不同种源染色体荧光带型的研究

分析了我国南方主要树种马尾松7个种源染色体的两种荧光带型，色霉素A3（简称CMA带）和4，6－二脒基－2－苯基咪哚（简称DAPI带）。结果表明：（1）马尾松染色体的CMA带型中存在着5种不同类型，它们分别是1对为着丝粒和臂间处均有荧光带的中间着丝粒染色体（A类型）；6对为臂间处有荧光带的中部着丝粒染色体（B类型）；1对为着丝粒处有荧光带的中部着丝粒染色体（C类型）；3对为无荧光带的近中部中部着丝粒染色体（D类型）；1对为着丝粒处有荧光带的近中着丝粒染色体（E类型）。其CMA带型公式2n=24=2A 12B 2C＋6D＋2E。（2）根据CMA的带型状况，将马尾松的7个种源分为2种类群区，第一类为江西吉安，福建漳平，贵州贵阳，四川古蔺和湖南宜樟为中部区；第二类为广东高州和广西宁明为南部区。（3）比较马尾松7种源的DAPI带型，南部区种源的染色体上的荧光带纹较中部区种源染色体上荧光带纹要多些，西部区种源染色体上的荧光带纹较东部区种源染色体上的荧光带纹亦要多些。     

Similar level of polyteny in bands and interbands of Drosophila giant chromosomes

The giant polytene chromosomes of Drosophila melanogaster have long been of interest to the geneticist because of the visible map of the genome provided by their characteristic banding patterns. An issue in the understanding of the molecular basis of chromosome banding has been whether the chromosomal DNA is replicated to the same extent in bands and interbands. Although various suggestions have been put forward the point has remained controversial. We have isolated 315 kilobases (kb) of contiguous Drosophila genomic DNA which spans an interval of approximately 13 bands and interbands of the polytene chromosomes. We report here the measurement of the relative level of DNA replication in polytene chromosomes of 84 adjacent restriction fragments of our cloned DNA. We conclude that there are no significant differences in the level of polyteny within the large band and between bands and interbands of this region. This result supports the 'folded fibre' model of polytene chromosome organization, rather than models involving disproportionate replication along the banding pattern.     

Dependence of Z-DNA antibody binding to polytene chromosomes on acid fixation and DNA torsional strain

There is considerable interest in the existence and significance of alternative conformations of DNA to the right-handed B-form described originally by Watson and Crick. The indirect immunofluorescence observations of Nordheim et al., Arndt-Jovin et al. and Lemeunier et al. that antibodies against left-handed Z-DNA bind to polytene chromosomes have thus assumed considerable importance. However, there is a paradox: some workers observe Z-DNA in interbands and others in bands. We report here that binding of Z-DNA antibodies to Drosophila polytene chromosomes prepared without acid fixation is at background level, and that following acid fixation the same antibody treatment leads to intense fluorescence. Depending on the extent of exposure to 45% acetic acid, fluorescence can occur primarily in interbands or in bands. Furthermore, antibody binding is dependent on elastic torsional strain in the DNA molecules.     

Three-dimensional architecture of a polytene nucleus

The three-dimensional chromosome topography in an intact nucleus has been determined using fluorescently stained Drosophila polytene chromosomes, optical fluorescence microscopy and newly developed, generally applicable, cellular image reconstruction techniques. The folding pattern is a complex mixture of parallel chromosomal segments and intertwined coils and shows extensive interaction of the chromosomes with the nuclear envelope.     

Characteristic folding pattern of polytene chromosomes in Drosophila salivary gland nuclei

A computer-based system for recording and analysing light microscope images, combined with classical cytogenetic analysis, has revealed the spatial organization of the giant chromosomes of Drosophila salivary gland cells. Each polytene chromosome arm folds up in a characteristic way, contacts the nuclear surface at specific sites and is topologically isolated from all other arms.     

Chromosomal clustering of muscle-expressed genes in Caenorhabditis elegans

Chromosomes are divided into domains of open chromatin, where genes have the potential to be expressed, and domains of closed chromatin, where genes are not expressed. Classic examples of open chromatin domains include 'puffs' on polytene chromosomes in Drosophila and extended loops from lampbrush chromosomes. If multiple genes were typically expressed together from a single open chromatin domain, the position of co-expressed genes along the chromosomes would appear clustered. To investigate whether co-expressed genes are clustered, we examined the chromosomal positions of the genes expressed in the muscle of Caenorhabditis elegans at the first larval stage. Here we show that co-expressed genes in C. elegans are clustered in groups of 2-5 along the chromosomes, suggesting that expression from a chromatin domain can extend over several genes. These observations reveal a higher-order organization of the structure of the genome, in which the order of the genes along the chromosome id correlated with their expression in specific tissues.     

Generating of rice OsCENH3-GFP transgenic plants and their genetic applications

In order to investigate rice functional centromeres, OsCENH3-GFP chimeric gene was constructed and transformed into the indica rice variety, Zhongxian 3037, mediated by Agrobacturium. The integration of the exogenous genes in the transgenic plants was confirmed by PCR and Southern blotting. The transgenic plants grow normally during their whole life time, just like Zhongxian 3037. No significant defects were detected in either mitosis or meiosis of the transgenic plants. The overlapping of GFP signals and anti-CENH3 foci in both mitotic and meiotic cells from T0 and T1 generation plants indicated that GFP had been successfully fused with CENH3, so the GFP signals can well represent the CENH3 locations on each chromosome. To evaluate the applicability of the transgenic plants to other genetic studies, fluorescence in situ hybridization （FISH） using rice centromeric tandem repetitive sequence CentO as the probe was conducted on the zygotene chromosomes of pollen mother cells （PMCs）. It has been revealed that the GFP signals are overlapping with CentO FISH signals, showing that CentO is one of the key elements constituting rice functional centromeres. Immunofluorescent staining using anti-o-tublin antibody and anti-PAIR2 antibody on the chromosomes during mitosis and meiosis stages of the transgenic plants further reveals that OsCENH3-GFP transgenic plants can be widely used for studying rice molecular biology, especially for tagging functional centromeres in both living cells and tissues.     

Spontaneous excision of a large composite transposable element of Drosophila melanogaster

The TE1 family of transposable elements (TEs) of Drosophila consists of unusually large transposons, cytologically visible in larval polytene chromosomes as one or more bands. They are composite elements, as their termini consist of foldback (FB) sequences which are themselves transposable. The location of FB elements at the termini of transposable elements suggests that these sequences have a direct role in the genetic instability of TEs. To investigate the structural and phenotypic consequence of TE excision, we have cloned genomic DNA required for the expression of the no-ocelli (noc) gene of Drosophila; this gene has been mutated by the insertion of TE146, a member of the TE1 family carrying six polytene chromosome bands including functional copies of the white (w+) and roughest (rst+) genes. As reported here, our experiments indicate that the spontaneous excision of TE146, which results in the loss of the w+ and rst+ markers, can occur either as a single-step event or following a partial internal deletion. In either case, the end product is an imprecise excision in which a residual portion of the element, varying in size from 3 to 10 kilobases (kb), is left at the insertion site. These residual sequences share homology with the FB family. Furthermore, despite their imprecise nature, all these spontaneous excisions restore a wild-type noc+ phenotype.     

野生二粒小麦的Giemsa C带核型

采用改良C带技术对野生二粒小麦根尖细胞染色体进行了分带研究结果表明：野生二粒小麦体细胞中有14对染色体，染色体组型AABB不同染色体上带的数目、大小、强弱及分布情况各异，而同源染色体的带型一致，根据C带带型特征很容易将野生二粒小麦不同染色体组、及不同染色体分开因此，C带可作为野生二粒小麦的细胞学标记．此外，除4B染色体外，野生二粒小麦染色体的C带带型特征与普通小麦相应染色体相似，这从染色体结构方面进一步证实了野生二粒小麦是普通小麦祖先种之一的假设