云南泸定百合8个野生居群的染色体核型分析

用常规压片法,对云南省境内泸定百合(Lilium sargentiae Wilson)8个野生居群的染色体进行了核型分析,结果显示:(1)野生泸定百合8个居群均为二倍体(2n=2x=24),染色体基数为12,共24条染色体,无B染色体;(2)核型类型均为3A,第1、2对染色体均为具中部(m)或近中部(sm)着丝点的大形染色体,且第1对染色体上均具有随体;(3)染色体长度比为1.64～2.26,平均臂比为6.43～8.22,核型不对称系数为79.82% ～ 81.77%。研究表明,泸定百合染色体数相对稳定,染色体变异主要表现在结构变异,各个居群的染色体组成、随体数、随体位置、臂比、染色体长度比及核型不对称系数均有差异,泸定百合各居群间存在明显的核型多态性。     

紫万年青的核型分析

本文采用直接敲片法制作紫万年青植物染色体标本,通过体细胞染色体计数确定其染色体数目为12条,核型分析表明紫万年青植物染色体总长度为57.35μm,全组染色体平均长度9.56μm,其核型公式为K(2n)=12=3m+3Sm.同时通过观察、测量发现其染色体绝对长度变异范围为11.36～7.72μm,其相对长度组成为2n=12=6M2+6M1;最长染色体与最短染色体之比为1.47:1,臂比的变异范围为1.01～2.56,臂大于2的染色体占全组染色体的33.33%,属于"2A"类型.另一方面,间期附加核型特征确定紫万年青属于复杂染色中心型.本研究将对紫万年青植物的起源、系统演化及品种改良等提供必要的细胞遗传学依据.     

核型不对称性的一种定量测定法及其在进化研究中的应用

本文提出了一种测定核型不对称性的定量方法。决定核型不对称性的两变量是染色体臂比和相 对长度。核型全部染色体臂比等于1,且长度彼此相等时,称该核型为理想对称核型。任一实际观测核型与理想对称核型的差异用臂比不对称系数D_c和长度不对称系数D_t度量。以D_c和D_l作座标可以绘制二维平面图。不同居群或分类群依其核型不对称性在平面图中有其确切的相对位置,进而反映出其间在细胞学上的关系及核型变异趋势。     

中国特有的八角莲和六角莲的核型

本文研究了八角莲Dysosma versipellis(Hance)M.Cheng和六角莲Dysomapleiantha((Hance)Woodson的核型。二者的染色体数目均为2n=12,由四对具中部着丝点染色体、一对具近中部着丝点染色体和一对具端部着丝点染色体组成,各有一对染色体具有次缢痕,八角莲的次缢痕在第3对染色体的长臂上,六角莲的次缢痕在第1对染色体的短臂上。二者均属较对称的“2A”核型。但它们在染色体相对长度的变异幅度和差值、臂比的变异幅度和差值以及最长与最短染色体的比值上均有微小的差异。结果表明二者有密切的亲缘关系。演化趋势是八角莲→六角莲。八角莲的核型为首次报道。     

中国特有的八角莲和六角莲的核型

本文研究了八角莲Dysosma versipellis(Hance)M.Cheng和六角莲Dysomapleiantha((Hance)Woodson的核型。二者的染色体数目均为2n=12,由四对具中部着丝点染色体、一对具近中部着丝点染色体和一对具端部着丝点染色体组成,各有一对染色体具有次缢痕,八角莲的次缢痕在第3对染色体的长臂上,六角莲的次缢痕在第1对染色体的短臂上。二者均属较对称的“2A”核型。但它们在染色体相对长度的变异幅度和差值、臂比的变异幅度和差值以及最长与最短染色体的比值上均有微小的差异。结果表明二者有密切的亲缘关系。演化趋势是八角莲→六角莲。八角莲的核型为首次报道。     

基于比较核型分析方法追溯百合族 (百合科) 二型性核型的起源

百合族具有非常一致的二型性核型,由4条长染色体以及20条短染色体组成。目前有两个假说解释其二型性核型的来源,着丝粒横裂和多倍化。但是,具体是哪一种机制起主要作用仍然不清楚。根据文献以及自己的实验结果,我们整理并重新分析了百合亚科和美德兰亚科所有属的核型资料。比较核型分析结果表明,来自单条染色体的特征、染色体臂数、核型不对称性以及染色体的相对长度诸方面的证据都支持着丝粒横列是百合族核型进化的主要机制,但不能排除其它的机制也在起着作用,如臂间倒位和易位。臂间倒位和易位可能在郁金香族的核型进化中起着主要的作用。另外,本研究还报道了三个种的核型,粗茎贝母 (Fritillaria crassicaulis)、准格尔郁金香 (Tulipa suaveolens) 和尖果洼瓣花 (Gagea oxycarpa)。     

柏科的细胞分类学研究

柏科Ｃｕｐｒｅｓｓａｃｅａｅ含１１５－１２５种,隶２０属,广布于两半球。该科迄今已有１４属５５种植物作过核型分布析,分别以平均臂比和染色体长度比为纵,横座标的各植物核型座标点的相对中以反映出它们的进化趋势及相互亲缘关系。     

不同产地木耳菜的染色体核型分析

为了研究木耳菜核型特征及不同产地间的进化关系,以来自7个产地的8个木耳菜品种为材料,采用常规压片法进行核型分析,并进行核型进化趋势分析和主成分分析。结果表明:(1)所有木耳菜的染色体数目均为2n=2x=44,未见异常染色体,染色体类型均为中部着丝粒染色体(m)或近中部着丝粒染色体(sm),且m数量多于sm。(2)不同产地的木耳菜在染色体核型公式、核型类型、随体位置、染色体长度比、臂比及核型不对称系数等指标均存在明显差异;随体均为1对,但随体位置不同。(3)核型类型为1A、1B和2A型,其中1A型5种,数量最多。(4)染色体长度比范围为1.51~2.06,平均臂比值范围为1.30~1.48,仅有吉林‘利丰’和江西‘航城’存在臂比大于2的染色体。(5)核型不对称系数范围为56.25%~59.17%,核型的对称程度较高,推测木耳菜的进化程度较为原始,其中河北‘金发’是最原始,江西‘航城’最进化。研究结果为木耳菜的细胞遗传学研究提供了参考依据。     

韭菜三个品种的核型研究(摘要)

本文研究了我国不同地区韭菜三个品种(尸州韭、青岛韭、银川韭)的核型。结果表明:三个品种的核型均为同源四倍体,其核型公式为2n=4x=32=28m+4st(SAT),第1—7号为具中部着丝点染色体,第8号为近端着丝点染色体并带有随体,但其中有二个染色体带有明显的随体,另二个染色体所带随体较难以分辨。三个不同品种之间,染色体全组总的长度、染色体相对长度、最长和最短的变异范围、臂比范围都存在一些差异,但并不显著。本实验不同品种韭菜的核型研究结果与文献记载相符,不同者为第8对带随体染色体为具中部着丝点。而有的作者测定为近端着丝点染色体。此外,对于带随体染色体类型的不同与随体显现的程度进行了初步讨论。     

杉科的两条演化路线

本文根据核型资料提出杉科可能存在A、L两条演化路线,前者包括由原始到进化的柳杉属、水 松属、落羽杉属、台湾杉属,以平均臂比快速增加、染色体长度比缓慢增加为特征;后者包括依序进化的水杉属、巨杉属、红杉属、杉木属(可能还有密叶杉属),以平均臂比缓慢增加、染色体长度比迅速增加为特点。该结论也得到形态学、解剖学、胚胎学等资料的支持。     

籼,粳稻及其杂种粗线期的核型分析

研究了典型籼,粳稻及其杂种粗线期的核型,结果表明：（１）籼稻品种南特号具有两对随体染色体,分别为第十和第十二染色体,粳稻品种巴利拉具１对随体染色体,为第十染色体,杂种南特号／巴利拉的随体染色体与南特号相同;（２）在粗线期,两品种均可见单核仁和双核仁的细胞存在,说明细胞贩核仁数目与随体数目并不对应;（３）两品种的对应染色体之间,在染色体相对长度,臂比及染色粒分布上均无明显差异。     

Somatic chromosomes of higher diptera

Summary The chromosome complements of eighty brain cells ofHylemya antiqua have been studied. The eighty cells were found in thirty-three larvae. Total complement length (TCL) is not randomly distributed among the larvae. Because there is an inverse correlation between chromosome length and width, it appears that in the cells studied the different chromosome lengths are partly expressions of different stages of metaphase contraction. It is suggested that synchronous division of cells still occurs in late larvae.The length of each chromosome arm is highly correlated with that of every other arm. It is possible that the correlations are complete but that inadequate technique causes the departures from completeness which are observed. The chromosome lengths are corrected slightly for distortions, but the corrections make very little difference in the correlation coefficients. There is a high value for the correlation between the correlation of two arm lengths and the sum of the two arm lengths. This is to be expected if the perfect correlation between all arm lengths is being obscured by errors of drawing and measurement.The autosomal arms have very similar coefficients of variation. The arm ratios (length of long arm divided by short arm) are not correlated with TCL or with each other, and arm ratio is randomly distributed among the larvae. The sex chromosomes have a smaller coefficient of variation than the autosomes, so that they are relatively large in small cells and relatively small in large cells.Twenty-two cells inHylemya fugax were measured. The autosomes also showed a high correlation between arm lengths. An entirely heterochromatic autosomal arm showed the same phenomenon of a low coefficient of variation which was shown by the heteropycnotic sex chromosomes inH. antiqua. The low variability of heterochromatic regions accompanied by an apparently non-random distribution of the TCL may produce an erroneous picture of the species complement when dealing with small numbers.It is suggested that for simplicity in using cytological observations of this sort for taxonomic purposes, the technique of measuring the percent TCL of a chromosome plus its arm ratio be replaced by the percent TCL of each arm plus the average length difference between the arms of each chromosome pair in units of percent TCL.     

辽宁产粗皮蛙的染色体组型研究(图版Ⅳ,下)

用骨髓细胞制片法分析了粗皮蛙的染色体组型 ,结果表明其二倍体染色体数为 2 6 ,可配成 13对 ,有5对大型染色体 (相对长度 >9)和 8对小型染色体 (相对长度 <6 5 ) ,其中 ,第 1、 5、 6、 7、 8对为中部着丝点染色体 ,第 12对为端部着丝点染色体 ,第 2、 3、 4、 9、 10、 11、 13对为亚中部着丝点染色体 ,第 4对为性染色体 ,属XY型 ,X染色体为亚中部着丝点 (相对长度为 10 70 ,臂比指数为 1 72 ) ,Y染色体为亚中部着丝点(相对长度为 12 83,臂比指数为 2 0 2 )。     

Frequency and sites of sister chromatid exchanges in rat kangaroo chromosomes

The frequency of sister chromatid exchanges in the chromosomes of a cell line from the Tasmanian rat kangaroo was determined to be 0.79 exchanges per chromosome for two cell cycles. Twenty-five percent of these exchanges occurred at the kinetochore. The mean frequency of exchanges per chromosomal arm was roughly proportional to the length of the chromosome, with the exception of a mean frequency of 0.20 exchanges per chromosome found at the kinetochore of all chromosomes, regardless of length. Thus, the kinetochore is a highly preferential site for sister chromatid exchanges. Compared to the main portion of the chromosomal arms the exchange frequency was somewhat lower adjacent to the kinetochore and at chromosome ends. The number of exchanges per unit length also tended to be lower for the short arm of chromosome 1. No correlation was found between the frequency of exchanges and late-replicating DNA.     

Densitometric and visual measurements of human chromosome 21

Summary The finding of heteromorphisms in certain regions of human chromosomes is useful in chromosome identification, especially in the study of the origin of nondisjunction. Quantitation of heteromorphisms in the smaller human chromosomes is theoretically valuable but remains technically difficult. In this paper we evaluate two methods for quantitation of human chromosome 21—visual and densitometric measurement of Q-banded 35-mm negatives. Thirteen parameters are defined for chromosome 21. We find three of them to show less variability between different measurements of the same cell and from cell to cell in the same individual: (1) the centromere index, defined as the ratio of length of the satellite, stalk, and short arm to the length of the satellite, stalk, and short and long arms; (2) the ratio of length of the satellite to the length of the total heteromorphic region of the short arm; and (3) the ratio of the short arm intensity to the intensity of band q21. Another parameter, the ratio of satellite intensity to the intensity of band q21, is reproducible by visual measurement but not by densitometry. Based on these studies we conclude that densitometry is not necessarily better than visual quantitation of the heteromorphic region of chromosome 21.     

The chromosome complement of the Rhesus monkey (Macaca mulatta) determined in kidney cells cultivated in vitro

Summary The chromosome complement of male and female Rhesus monkey has been investigated in kidney cells cultivatedin vitro for 3 to 6 days. The chromosome number is 42. The Y chromosome of the heterogametic male is the smallest element in the complement, and it is acrocentric. The X chromosome ranks eigth in decreasing order of size and typically has an arm ratio of 1.4. The autosomes form a graded size series of metacentric chromosomes, 3–15μ long in early metaphase, and with arm ratios from 1.1 to 3.3. Chromosome IX carries a large secondary constriction near the centromere; it is presumed to be the main nucleolar chromosome. A smaller secondary constriction is found consistently in the long arm of chromosome I. The X chromosome and chromosome XXI appear to be dimorphic in the limited population studied, the alternative forms differing in arm ratios but not in total length. An idiogram of the haploid chromosome complement is presented incorporating measurements of 10 completely analyzed nuclei, five from male monkeys and five from females. On the basis of relative length, arm ratio, and occurrence of secondary constrictions, most chromosomes of the complement can be individually identified. Supported in part by grants from the National Cancer Institute of Canada; the National Institutes of Health of the United States, Public Health Service; and the National Foundation for Infantile Paralysis.     

Karyotypes and C-banding patterns in species of Cyphomandra Mart, ex Sendtner (Solanaceae)

The orcein and C-banded karyotypes of 11 species of Cyphomandra (Solanaceae) were described. All species were diploid with 2n = 2x = 24. The chromosomes were large, ranging from 4 to 10 u.m iⁿ length, and in each complement were largely metacentric or submetacentric with few subtelocentrics. There was a significant negative correlation between chromosome length and arm ratio within a complement as well as between taxa. In general, chromosomes of the larger complements were more symmetrical in terms of both relative chromosome length and arm ratio, implying that similar amounts of DNA had been added to or taken away from every chromosome are of each complement during evolutionary divergence. Two pairs of non-homologous chromosomes were seen to contain subterminal secondary constrictions in most species. The two Brazilian species studied differed from those of Andean origin in the location of one of these secondary constrictions, suggesting a major evolutionary divergence between these two groups of specieS. Non-homologous chromosomes were difficult to distinguish from one another without the aid of C-banding, due to a continuum in the distribution of chromosome lengths and arm ratios. Telomeric and interstitial bands were shown in all species but not all chromosomes in each complement were banded. There were no centromeric bandS. Nuclear DNA amount and the length, but not proportional length, of C-bands were correlated in each specieS. One species ( C. Luteoalba (Pers.) Child, section Cyphomandropsis ) was unique in its banding pattern, providing further evidence for the delimitatation of this species and perhaps section from other Cyphomandra taxa.     

同一生境下多年生黑麦草与节节麦的核型比较

对同一生境下多年生黑麦草（Lolium perenn L.）和节节麦（Aegilops squarrosa L.）的根尖细胞染色体作了分析,并从细胞学角度比较了两者的同源性。结果表明：多年生黑麦草的核型公式为：2n=6x=42=24m＋18sm（2SAT）,属于六倍体的＂2B＂型,在第19号染色体上有一对随体,最长与最短染色体的比为2.13,臂比大于2的染色体占全套染色体的30%,核型不对称系数为60.48%;节节麦的核型公式为2n=2x=14=10m＋4sm（2SAT）,属于二倍体的＂2A＂型,在第4号染色体有一对随体,最长与最短染色体长度比为1.49,臂比大于2的染色体占全套染色体的14%,不对称系数为58.2%,表明同一生境下多年生黑麦草比节节麦更为进化,两者在染色体水平上没有亲缘关系。     

福建壳斗科部分植物染色体计数及核型分析

采用去壁低渗法处理根尖细胞,得到了壳斗科13种植物分散较好的细胞中期分裂相,并分析了其中9种植物的染色体数目、随体数目和位置、核型公式、核型类型、臂比、相对长度、着丝点指数、核型不对称系数等内容。结果表明:除东南石栎属1B型外,其他均属2B型,K(2n)=24,在植物界属小染色体类型。     

A hemicentric inversion in the maize line knobless Tama flint created two sites of centromeric elements and moved the kinetochore-forming region

A maize line, knobless Tama flint (KTF), was found to contain a version of chromosome 8 with two spatially distinct regions of centromeric elements, one at the original genetic position and the other at a novel location on the long arm. The new site of centromeric elements functions as the kinetochore-forming region resulting in a change of arm length ratio. Examination of fluorescence in situ hybridization markers on chromosome 8 revealed an inversion between the two centromere sites relative to standard maize lines, indicating that this chromosome 8 resulted from a hemicentric inversion with one breakpoint approximately 20 centi-McClintocks (cMc) on the long arm (20% of the total arm length from the centromere) and the other in the original cluster of centromere repeats. This inversion moved the kinetochore-forming region but left the remainder of the centromere repeats. In a hybrid between a standard line (Mo17) and KTF, both chromosome 8 homologues were completely synapsed at pachytene despite the inversion. Although the homologous centromeres were not paired, they were always correctly oriented at anaphase and migrated to opposite poles. Additionally, recombination on 8L was severely repressed in the hybrid.