中国五种高山锄足蟾的核型、Ag-NORs和C-带的研究

作者用核型、Ag-NORs和C-带,对分布于川、滇两省的二属(齿突蟾、齿蟾)五种(胸腺齿突蟾、圆疣齿突蟾、凉北齿蟾、秉志齿蟾、疣刺齿蟾)锄足蟾作了属间和种间关系的比较分析,并讨论了它们的核型演化机制。结果表明:(1)齿突蟾和齿蟾两属间在核型和带型上都有明显的差异,演化途径主要的可能是含有重复DNA染色体片段的相互易位或臂间倒位;(2)属内不同种之间带型无显著差异,但某些对应染色体对间,其相对长度和臂比值差异明显,十分可能是常染色质片段的易位和臂间倒位所致;(3)凉北齿蟾有染色体数目变异多态现象;(4)五种锄足蟾均未发现异形性染色体。     

云南三种角蟾的细胞遗传学研究

本文研究了云南三种角蟾的核型,C－带和Ag-NORs,结果显示宽头大角蟾,其2n=26(16M 8SM 2T),NF=50,5 8,No.10为T,次缢痕和Ag－NORs位于1p per,该区域同时还呈现C－带正染,其全部染色体的着丝点都有强弱不等的C－带染色;大花角蟾的核型2n=26(16M 8SM=2ST),NF＝50,5＋8,No.6为ST,次缢痕和Ag-NORs位于5q pes,全部着丝点均有C－带正染;凹顶角蟾5n=26(16M 4SM 6T),NF=46,6 7.No.11-13为T,次缢痕和Ag-NORs位于5q per,全部着丝点及周围均有浓C－带正染。三个种均未发现与性别相关的异形染色体,最后讨论了角蟾属核型演化的途径。     

白鱀豚的核型及其C－带核型的研究

采用常规的白细胞培养技术及ＢＳＧＣ－带技术分析了白豚的核型、Ｃ－带核型。结果是：白豚的染色体数目２ｎ＝４４,其核型由１２条中部着丝点染色体、１８条亚中部着丝点染色体、４条亚端部着丝点染色体、８条端部着丝点染色体和２条性染色体所组成。染色体臂数（ＮＦ）雌性为７６,雄性为７５。Ｃ－带异染色质呈现出很深的着色区,主要分布在染色体臂上,着丝点区则几乎没有。Ｃ－带异染色质的量约为总染色质量的１２％。这一结果表明白豚与海生豚类的核型、Ｃ－带核型有较明显的相似性。     

棕色田鼠的细胞遗传学研究

本次首次报告棕色田鼠（Microtus mandarinus)的核型,核型公式为2n=50=2(M,T) 2SM 44T XX(M,SM),XY(SM,ST),发现第一对常染色体及X性染色体存在多态现象,在所研究的15只雌性个体中有7只雌性个体的细胞只有1条X性染色体,性染色体组成为XO型,核型公式为2n=49=2(M,ST) 2SM 44T＋XO,。其中X性染色体不同于雄性中的X（SM）,为M类型,本文提出的综色田鼠3种核型与Brown等人（1964）提出的Microtus oregoni的3种核型（XO,YO,XY）有异,本文还阐述了染色体多态产生的机制和探讨了XO型个体发生的机理及其繁殖。     

Biogeographic patterns in the chromosomal distribution of a satellite DNA in the banded tetra Astyanax fasciatus (Teleostei: Characiformes)

The As-51 satellite DNA is a transposon-like sequence formerly described for arthropods and physically identifiable by fluorescent in situ hybridization. In the present work, we describe the occurrence of this sequence, as well the C-banding and karyotype composition, in populations of the group Astyanax fasciatus from Mogi-Guaçu (Araras-SP), Paranapanema (Angatuba and Pilar do Sul-SP), Ribeira de Iguape (Sete Barras-SP) and Tietê (Indaiatuba and Salesópolis-SP) river basins. The specimens from Sete Barras (10 M + 20SM + 12ST + 6A) and Araras (8 M + 22SM + 12ST + 6A) have 2n?=?48 chromosomes. The samples from Angatuba, Pilar do Sul and Indaiatuba presented 2n?=?46 chromosomes (12 M + 20SM + 10ST + 4A). The individuals collected in Salesópolis showed three cytotypes, bearing 2n?=?46 (12 M + 20SM + 10ST + 4A), 2n?=?48 (8 M + 22SM + 12ST + 6A) and 2n?=?50 (8 M + 16SM + 14ST + 12A). C-banding revealed large heterochromatic blocks at terminal chromosomal regions in all populations and/or cytotypes. All analyzed populations have conspicuous blocks carrying the As-51 satellite DNA, although the number of chromosomes bearing this repetitive sequence was variable among them. Such differences were not related to the diploid number of individuals, but rather to a biogeographic pattern. Aspects of the karyotype evolution and distribution of this sequence in distinct populations are discussed.     

Evidence of species specific pericentric inversion in the karyotype of the midge Chironomus balatonicus

Pericentric inversions do not play any important role in chromosomal rearrangements in the karyotype evolution of the genus Chironomus. However, a unique case of the fixed pericentric inversion was discovered in chromosome 2 of Chironomus balatonicus--one of the members of plumosus-species group (Kikhadze et al., 1996a; Golygina et al., 1996). According to morphological criteria, a centromere band on chromosome 2 changed its position in Ch. balatonicus. The cloned H3-SauDNA, specific for centromeres in plumosus group, was in situ hybridized with Ch. balatonicus polytene chromosomes, and thus a real change in the centromere position was proved to be a result of pericentric inversion. This was also confirmed after differential C-staining.     

三种食肉目动物的核型分析

本文报道了产于我国华北地区的艾鼬、貉和果子狸的核型。其中艾鼬2n=36。组型由20条双臂染色体、14条单臂染色体和一对性染色体组成。貉2n=65,它与wuster等报道过的貉的2n=42的核型表现出同种动物核型间的多态现象。果子狸2n=44,其c带带型中具有一对带有较大异染色质的中部着丝点染色体。     

Molecular characterization of the pericentric inversion of chimpanzee chromosome 11 homologous to human chromosome 9

In addition to the fusion of human chromosome 2, nine pericentric inversions are the most conspicuous karyotype differences between humans and chimpanzees. In this study we identified the breakpoint regions of the pericentric inversion of chimpanzee chromosome 11 (PTR 11) homologous to human chromosome 9 (HSA 9). The break in homology between PTR 11p and HSA 9p12 maps to pericentromeric segmental duplications, whereas the breakpoint region orthologous to 9q21.33 is located in intergenic single-copy sequences. Close to the inversion breakpoint in PTR 11q, large blocks of alpha satellites are located, which indicate the presence of the centromere. Since G-banding analysis and the comparative BAC analyses performed in this study imply that the inversion breaks occurred in the region homologous to HSA 9q21.33 and 9p12, but not within the centromere, the structure of PTR 11 cannot be explained by a single pericentric inversion. In addition to this pericentric inversion of PTR 11, further events like centromere repositioning or a second smaller inversion must be assumed to explain the structure of PTR 11 compared with HSA 9.     

彭泽鲫两个雌核发育克隆的染色体组型分析

采用PHA和秋水仙素体内注射法直接制作肾细胞染色体标本,对彭泽鲫种群内两个不同雌核发育克隆的亲本进行染色体数目及组型分析。结果表明,彭泽鲫种群内的两个不同克隆存在染色体数目及组型差异,其中克隆H包含6条超数染色体在内的染色体众数是156,150条基本染色体的组型公式为：42M 36SM 39ST 33T,NF=228;克隆L包含12条超数染色体在内的染色体众数是162,150条基本染色体的组型公式为：36M 45SM 33ST 36T,NF=231。两个不同雌核发育克隆的发现及其染色体的差异说明彭泽鲫种群内同样存在着类似银鲫种群内的遗传多样性。     

Karyological study of the dolly vardenSalvelinus malma from Alaska

The karyotype of the dolly vardenSalvelinus malma from Alaska was analysed. A pair of huge acrocentrics, which could have resulted from either tandem fusion or centric fusion followed by pericentric inversion, was observed. Ag-NORs were observed at the terminal regions of the second largest chromosome pair, and individual size-differences in Ag-NORs and in chromosomes with Ag-bands were found. From a comparison of the karyotypes of the dolly varden from Alaska and Hokkaido (Japan), karyotype differentiation by pericentric inversion and translocation was discussed.     

云南三种同域分布的棘蛙（蛙科Ranidae：无尾目Anura）的核型和银带研究

本文比较分析了云南景东地区三种同域分布棘蛙的核型和Ａｇ－ＮＯＲｓ。花棘蛙２ｎ＝２６（１６Ｍ＋ １０ＳＭ）,ＮＦ＝５２,次缢痕和Ａｇ－ＮＯＲｓ位于１ｐｉｎｔｅｒ,Ｎｏｓ．２－４,８,９等为ＳＭ。棘肛蛙２ｎ＝４０（１６Ｍ＋ ２０ＳＭ＋２ＳＴ＋２Ｔ）,ＮＦ＝７８,Ｎｏｓ．５－９,１１－１３,１５,１７等１０对为ＳＭ,Ｎｏ．３为ＳＴ,Ｎｏ．１８为Ｔ,其余 均为Ｍ,Ａｇ－ＮＯＲｓ位于１１Ｐ。二种的Ａｇ－ＮＯＲｓ都有异形现象。双团棘胸蛙２ｎ＝６４Ｔ,次缢痕和Ａｇ－ ＮＯＲＳ在４ｑｐｅｒ。都未发现异形性染色体。最后,对棘蛙属的核型演化机制和物种形成方式作了讨论。     

Molecular Definition of Pericentric Inversion Breakpoints Occurring during the Evolution of Humans and Chimpanzees

High-resolution G-banding analysis has demonstrated remarkable morphological conservation of the chromosomes of the Hominidae family members (humans, chimpanzees, gorillas, and orangutans), with the most notable differences between the genomes appearing as changes in heterochromatin distribution and pericentric inversions. Pericentric inversions may have been important for the establishment of reproductive isolation and speciation of the hominoids as they diverged from a common ancestor. Here the previously published primate karyotype comparisons, coupled with the resources of the Human Genome Project, have been used to identify pericentric inversion breakpoints seen when comparing the human karyotype to that of chimpanzee. Yeast artificial chromosome (YAC) clones were used to detect, by fluorescencein situhybridization, five evolutionary pericentric inversion breakpoints present on the chimpanzee chromosome equivalents of human chromosomes 4, 9, and 12. In addition, two YACs from human 12p that detect a breakpoint in chimpanzee detect a similar rearrangement in gorilla.     

Meiotic analysis of a pericentric inversion, inv(7) (p22q32), in the father of a child with a duplication-deletion of chromosome 7

In a family in which a large pericentric inversion of chromosome 7 is segregating, two of the four progeny of inversion heterozygotes show severe psychomotor retardation and have the karyotype 46,XX,rec(7),dup q,inv(7)(p22q32), derived from crossing-over within the inversion. Meiotic analysis in one of the heterozygotes revealed no evidence of inversion loops in well-spread pachytene cells. In approximately 20% of cells in diakinesis, the presumptive bivalent 7 had only one chiasma. Two alternatives to the reversed loop mode of meiotic pairing of inversions are proposed. Review of the literature supports the view that "small" pericentric inversions have a much better genetic prognosis than "large" pericentric inversions.     

洞庭湖水系沅水和澧水野鲫的染色体组型及资源保护

鲫(Carassius auratus)是洞庭湖水系一种重要的经济鱼类。为了解洞庭湖水系野鲫的细胞遗传背景,采用PHA和秋水仙素活体注射法,对沅水和澧水采集的野鲫样本逐一进行肾细胞染色体制片及组型分析。结果发现,在两条河流的野鲫群体中均检测出染色体数为100和基本染色体数为150的两种不同倍性个体,其中,两条河流染色体数为100的二倍体鲫组型公式为2N=28M+22SM+28ST+22T,NF=150;基本染色体数为150的三倍体鲫组型公式为3N=42M+33SM+42ST+33T,NF=225。在沅水和澧水不同采样点随机采集的共100尾野鲫中,检测出的三倍体比例(85%)远高于二倍体(15%),且二倍体与三倍体鲫个体在形态特征上不存在明显差异(P0.05)。两种不同倍性鲫在同一水体的共存对于鲫的遗传进化与选育具有一定的理论和实践意义,而二倍体鲫种群的大量减少,则提示我们应该从染色体组遗传多样性角度加强对洞庭湖水系二倍体野鲫资源的保护。     

Chromosome and C-heterochromatin polymorphisms in the Italian newt,Triturus italicus

A combined chromosome and C-heterochromatin polymorphism in pair 12 in the complement of the newt species, T. italicus is described. The C-heterochromatin polymorphism is presumably due to a loss in the proximal C-band, whereas the chromosomal polymorphism has its origin in two different independent pericentric inversions both including the centromere and the proximal C-band of chromosome 12. The double-inversion polymorphism has a wide distribution over the range and follows a clear bipolarity between a northern area where the karyotype is homomorphic for the standard type of pair 12 (ST/ST) and an opposite area where the ST type is completely replaced by variant M₁ and M₂ metacentric chromosomes 12. Various karyophylogenies are possible, but the simplest and the most probable presumes an ancestral karyotype of ST/ST and a mechanism of gradual replacement of the heterobrachial chromosome ST by two independent pericentric inversions. The present data are discussed in relation to existing theories on karyological evolution of Urodeles and the functional significance of telocentric chromosomes suggested by Sessions et al. (1982).     

Conditions for Protected Inversion Polymorphism under Supergene Selection

Conditions for protected inversion polymorphism under the operation of both karyotype and supergene selection in a viability model have been analytically determined. When supergene selection (the effect of recombination in homokaryotypes lowering the mean fitness of their offspring) is acting on gene arrangements and there is no karyotype selection, it is demonstrated that a polymorphic stable equilibrium is reached by the population, which is a function of only the recombination effects in homokaryotypes. Under both supergene and karyotype selection the degree of dominance (h) of karyotype selection is critical to produce a protected inversion polymorphism. In general, the opportunity for protected polymorphism increases as the degree of dominance decreases. For small s values, the conditions for protected polymorphism are r > 2sh and c > 2s(h - 1), where r and c are the average loss of viability for offspring of ST/ST and IN/IN homokaryotypes, respectively. These findings suggest that supergene selection may be an important balancing mechanism contributing to the maintenance of inversion polymorphism.     

Chromosomal evolution in the Brazilian lizards of genus Leposoma (Squamata, Gymnophthalmidae) from Amazon and Atlantic rain forests: banding patterns and FISH of telomeric sequences

An extensive karyotype differentiation was found among three species of gymnophthalmid lizard genus Leposoma which occur in the tropical forest areas of Brazil. We examined the chromosomes of the Amazonic species L. guianense (LOU) and L. oswaldoi (LOS) and the Atlantic forest species L. scincoides (LSC) after conventional and differential staining, and FISH of telomeric sequences. Both Amazonic species shared very similar 2n = 44 karyotypes, including 20 biarmed macrochromosomes and 24 microchromosomes (20 M + 24 m). However, the location of Ag-NORs and the amount of constitutive heterochromatin differed in these karyotypes. The Atlantic forest species L. scincoides has a very distinct karyotype with 52 acrocentric and subtelocentric chromosomes of decreasing size. Comparative R-banding analysis revealed complete homeology of the macrochromosomes of LGU and LOS and correspondence of banding patterns between LSC acrocentrics and subtelocentrics and some arms of biarmed LGU and LOS chromosomes. Pair 1 had similar banding patterns in the three species, implying the occurrence of a pericentric inversion. Interstitial telomeric bands (ITBs) detected by FISH at the pericentromeric region of some biarmed LGU and LOS chromosomes could be remnants of chromosomal rearrangements occurred during the differentiation of the karyotypes. Robertsonian rearrangements as well as pericentric inversions events probable were involved in the karyotype evolution of these Amazon and Atlantic forests species of Leposoma.     

染色体多态性与临床效应及生殖关系的探究

为了探讨人类染色体结构多态性与生殖异常临床效应的关系,按常规技术方法制备外周血淋巴细胞染色体,经G、C显带,对1 414例遗传咨询者进行核型分析,检出异常核型273例。其中多态性变异180例,占65.93%,非多态性异常核型93例,占34.07％。多态性变异包括D、G组短臂增长10例,次缢痕增长(包括1、9和16号染色体)35例,大Y染色体和小Y染色体 99例,Y染色体臂间倒位6例,9号染色体臂间倒位30例。结果表明,人类染色体多态性与流产、不孕不育、死胎、生育畸形儿等有相关性。     

鲤鱼染色体组人工调控的核型证明

以囊胚细胞制备鲤鱼单倍体染色体永久片并分析了单倍体染色体的核型。用囊胚细胞及白细胞培养法制取雌核二倍体及人工三倍体的永久片。以单倍体的核型为根据对人工二倍体及三倍体的染色体配对证明,人工诱发雌核二倍体的染色体是来自两个完整的染色体组,而人工三倍体的染色体则依不同个体而有差异。有部分个体的染色体来自三套完整的染色体组,但大部分个体是非整倍体,前者的雌性个体性腺发育正常,后者是不育的。