大麦G—显带核型的研究

本文报道了 ASG 法处理的三个栽培大麦(Hordeum Vulgare)品种 G-带的核型研究。结果表明无论是早中期或中期染色体都显示出了密切邻近的、多重的 G-带带纹。在有丝分裂过程中染色体愈浓缩带纹数目愈少。同源染色体之间带纹分布的位置、染色深浅以及带纹数目都基本一致,可以较为准确地进行配对。同一分裂时期不同染色体的 G-带带纹各具一定的特点,可以作为鉴别的标记。讨论了显带技术和中期染色体的 G-带等问题。     

Robertsonian change in allies ofZebrina (Commelinaceae)

Meiotic pairing inTradescantia soconuscana 2n=26 (6M+16A+4T) suggests that it has a tetraploid constitution which is not apparent in its chromosome number. Its nombre fondamental of 32 indicates that it could have evolved from an ancestor with x=8 by a combination of Robertsonian fusion, hybridization and polyploidy. The 2n=16 (8A+8T) karyotype of a closely related diploid supports this. The allied genusZebrina may have followed a similar method of chromosome evolution.     

SV40 T antigen alone drives karyotype instability that precedes neoplastic transformation of human diploid fibroblasts

To define the role of SV40 large T antigen in the transformation and immortalization of human cells, we have constructed a plasmid lacking most of the unique coding sequences of small t antigen as well as the SV40 origin of replication. The promoter for T antigen, which lies within the origin of replication, was deleted and replaced by the Rous sarcoma virus promoter. This minimal construct was co-electroporated into normal human fibroblasts of neonatal origin along with a plasmid containing the neomycin resistance gene (neo). Three G418-resistant, T antigen-positive clones were expanded and compared to three T antigen-positive clones that received the pSV3neo plasmid (capable of expressing large and small T proteins and having two origins of replication). Autonomous replication of plasmid DNA was observed in all three clones that received pSV3neo but not in any of the three origin minus clones. Immediately after clonal expansion, several parameters of neoplastic transformation were assayed. Low percentages of cells in T antigen-positive populations were anchorage independent or capable of forming colonies in 1% fetal bovine serum. The T antigen-positive clones generally exhibited an extended lifespan in culture but rarely became immortalized. Large numbers of dead cells were continually generated in all T antigen-positive, pre-crisis populations. Ninety-nine percent of all T antigen-positive cells had numerical or structural chromosome aberrations. Control cells that received the neo gene did not have an extended life span, did not have noticeable numbers of dead cells, and did not exhibit karyotype instability. We suggest that the role of T antigen protein in the transformation process is to generate genetic hypervariability, leading to various consequences including neoplastic transformation and cell death.     

Karyosystematic studies onRubiaceae: Chromosome counts from Sri Lanka

Chromosome numbers for 16 different taxa ofRubiaceae from Sri Lanka are presented. Counts for 13 species, including 5 genera and 1 tribe, are new. The results are listed, compared with available literature data and discussed in regard to their systematical importance.     

水杉的核型研究

本文观察了水杉的染色体,确定2n=22,核型公式为K(2n)=22m(2SAT),全具中着丝点,有一对随体。第8、10、11号染色体具“长着丝点区域”。属“1A”型,与北美红杉-AA的核型非常相近,可能是它的一个亲本种的直接后裔。     

植物幼嫩子叶的染色体制片

本文报道了用蚕豆(Vicia faba)、小巢菜(V. hirsuta)、豌豆(Pisum sativum)、菜豆(Phaseolus vulgaris)的幼嫩子叶作为研究体细胞有丝分裂及染色体的材料。与根尖比较,优点是:子叶细胞的有丝分裂活性高,组织易于解离和压片,且取材方便。     

Systematik,Verbreitung und Karyologie derFestuca violacea-Gruppe (Poaceae) im Ostalpenraum

The biosystematics of theFestuca violacea group (F. rubra subsp.violacea sensuHackel) in the Eastern Alps is studied.F. picturata Pils (=F. picta Kit. exSchultes nonJ. F. Gmelin) is confirmed as diploid, whereas the chromosome numbers forF. nitida (diploid),F. puccinellii (hexaploid), andF. norica (diploid, tetraploid and hexaploid) are reported for the first time. Details of morphology, leaf anatomy, and epidermal structures now allow a better separation of these species; new maps illustrate their distribution. Karyological, chorological, morphological, and anatomical data form the basis for a discussion of the phylogeny of theF. violacea group and its position withinF. rubra s. latiss.

     

Karyotype evolution in a tumour derived plant tissue culture analysed by Giemsa C-banding

Summary A hyperdiploid aneuploid karyotype, consisting of 7 chromosomes, has been found in a tumorous suspension cell culture ofCrepis capillaris (2 n=6). Giemsa C-banding has revealed that these 7 chromosomes show consistent patterns of differential staining in all dividing cells. This stable karyotypic situation has persisted during 18 months of cytological monitoring of the culture. Comparison with the diploid C-banded complement of the root tip indicates that numerous structural rearrangements must have occurred during the formation of the aneuploid complement. A likely pathway for evolution of this karyotype involves initial tetraploidy followed by chromosome loss. Such a mechanism has previously been proposed for a plant tissue culture system (Bayliss andGould 1974) and commonly occurs in animal systems, particularly in animal tumours (Terzi andHawkins 1975). An alternative mechanism, which does not necessarily involve tetraploidy, is also proposed.     

Recording mitotic chromosome cycle induction in living plant cells

Summary The presence of a prophase nucleus inHaemanthus endosperm happens to trigger the break down of the nuclear envelope in any interphase nucleus, located in its close proximity. Besides, chromosomes in the interphase nucleus start condensing gradually for the initial breaking point which is the nearest point to the prophase. The observation suggest the diffusion of an inducer, whose progression has been recorded to occur at a rate of 1.1 m/min.