The cytogenetics of Lotus (Leguminosae)

Chromosome numbers for 108 species of the genus Lotus (Leguminosae) are now known. This represents an increase of 32 new species which have been reported since a chromosome atlas for Lotus was published in 1965. At this rate, with just over one chromosome number being reported for a new species per year, it will require almost a century for the chromosome numbers to be determined for all of the species in the genus. A review of the cytogenetic features which have been observed in the genus through karyotype analyses, chromosome banding, Feulgen cytophotometry, anther culture, HCN reaction and interspecific hybridization is presented. These include cytomixis and B chromosomes (both found in hybrids of diploid species in the L. corniculatus group when L. alpinus was one of the parents), desynapsis, binucleate cell formation, polytene chromosomes in suspensor cells and trisomics in L. pedunculatus. There has been a reduction of HCN content in the species with evolutionary development which is correlated with basic chromosome number and geographic distribution. Classical karyotype analyses may not be a suitable method to investigate the parentage of L. corniculatus because of the chromosomal repatterning which has occurred during the evolutionary development of the closely related diploid species.     

纤毛鹅观草的形态学与细胞学观察

利用形态学和细胞学研究方法,对哈尔滨地区的纤毛鹅观草进行检测观察．结果表明,纤毛鹅观草为多年生植物,根茎发达,越冬性好,返青力强,植株抗病性和抗逆性表现突出．作为四倍体植物,染色体数目为2n=28．该研究为St染色体组在麦类作物和牧草遗传多样性的利用方面提供了理论基础．     

川厚朴染色体制作和核型分析研究

采用川厚朴新生愈伤组织为试验材料,进行染色体制作新方法的研究,并就川厚朴染色体核型进行了分析,其结果显示:川厚朴体细胞染色体数为2n=38,其中中部着丝点染色体(m)为16对,近中部着丝点染色体(sm)为2对,近端部着丝点染色体(st)为1对,其核型公式为K(2n)=38=32m 4sm(2SAT) 2st.     

临汾附近两种蛙类染色体特征研究

本文利用骨髓细胞空气干燥法，对临汾附近两种蛙类染色体组型进行分析．其中中国林蛙(Rana chensinensis)的二倍体染色体数目为2n＝24，包括12个大型染色体(相对长度大于7．0)和12个小型染色体(相对长度小于6，0)．全部染色体可配成12对．黑斑侧褶蛙(Pelophylax nigromaculata)的二部体染色体数目为2m＝26，全部染色体可配成13对，5对大型、8对小型染色体．与北京郊区同种蛙类染色体比较，说明不同地理居群的同种蛙染色体具有丰富的多样性．     

亚洲玉米螟染色体研究

本文首次报道亚洲玉米螟Ostrinia furnacalis Guenée(Lepidoptera:Pyralidae)的染色体核型。试验采用了压片法、空气干燥法和HSG显带法,观察并研究了亚洲玉米螟精巢中精母细胞的减数分裂和有丝分裂。五龄中期幼虫是减数分裂观察的最佳时期。染色体单倍体数目n=31,呈大小不等的小棒状或点状,有主缢痕。核型性别不明,性别决定机制不清。文中还对亚洲玉米螟精母细胞分化为精子过程中的各个分裂时期做了描述。     

家猪染色体C─带带纹量化记述法

本文首次报道家猪染色体Ｃ─带带纹量化记述法，该法将每个染色体上Ｃ─带带纹的发生位点，发生频率、带纹相对长度、和带形特征采用数据和符号相结合，并以表列的形式依次表述、简单明了、详细精确，它避免了现行方法对其进行逐一描述的繁赘性，和意断性。针对Ｃ─带带纹自身的多态性，一改对单个细胞进行分析为对一些细胞进行分析、力求从含行差异的个性中获得反映真值的共性，便于进行品种间和个体间的相互比较，和计算机阅读。     

染色体畸变与智力低下

在通常情况下,每种生物的体细胞中染色体的数目和结构都是恒定的,并且能稳定地遗传。如果染色体的数目或结构发生了变化(畸变),就改变了染色体上原来的基因顺序,基因数量或基因的组成,因此导致智力低下。     

六倍体小黑麦与普通小麦杂交细胞遗传的研究

本文报道了六倍体小黑麦与普通小麦杂交的性状与细胞遗传.共配制25个杂交组合,观察到以六倍体小黑麦为母本杂交当代结实率平均为36.17%,种子发芽率为80.14%,以普通小麦为母本杂交当代结实率平均为72.60%,幼胚在组织培养条件下出苗率为20.1%,F_1减数分裂中期有13.37个二价体和15.01个单价体,与理论数值接近.F_1的结实率正反交组合均很低,平均为2.98%,种子发芽率平均为32.38%.F_2的性状分离极其复杂,有三个主要类型即亲本类型与中间型,减数分裂中期二价体数变动在14-20间、单价体数变动在0-14间;根尖细胞用Giemsa染色进行C带分析.看到多有3-4对R组染色体,其中5R、6R、7R较多.F_1与亲本回交性状与染色体组型迅速恢复为亲本类型.在F_3及以后世代看到D、R组染色体混合类型是稳定的,可以从中选出多种类型的代换系.这种杂种方式对六倍体小黑麦性状的改进是有效的.     

Homologous recombination in fission yeast: Absence of crossover interference and synaptonemal complex

The study of homologous recombination in the fission yeastSchizosaccharomyces pombe has recently been extended to the cytological analysis of meiotic prophase. Unlike in most eukaryotes no tripartite SC structure is detectable, but linear elements resembling axial cores of other eukaryotes are retained. They may be indispensable for meiotic recombination and proper chromosome segregation in meiosis I. In addition fission yeast shows interesting features of chromosome organization in vegetative and meiotic cells: Centromeres and telomeres cluster and associate with the spindle pole body. The special properties of fission yeast meiosis correlate with the absence of crossover interference in meiotic recombination. These findings are discussed. In addition homologous recombination in fission yeast is reviewed briefly.This article is dedicated to Urs Leupold, the founder of fission yeast genetics.     

Karyotype and chromosome banding in the reed frogHyperolius viridiflavus ommatostictus (Amphibia,Anura, Hyperoliidae)

Summary C-banding and mithramycin staining were used to characterize the karyotypes of 10 specimens of the African reed frogHyperolius viridiflavus ommatostictus from Tanzania. The diploid chromosome number is 2n=24. Although no heteromorphic sex chromosomes were present in the mitotic karyotypes, in many diakineses of male meiosis one or two bivalents exhibited an end-to-end arrangement. In the laboratory 7 out of 24 females changed sex spontaneously. This indicates that an XY/XX system of sex determination operates inH. viridiflavus ommatostictus.This study was supported by the Deutsche Forschungsgemeinschaft (Schm 484/2-4). We thank K. E. Linsenmair and C. M. Richards for helpful comments on an earlier draft.