Genome relationships between octoploid and decaploid Thinopyrutn ponticum

MOUSTAKAS, M., 1993. Genome relationships between octoploid and decaploid Thinopyrum ponticum . The genomic relationships between octoploid and decaploid Thinopyrum ponticum were determined by computer-aided karyotype analysis. All the chromosome pairs of the octoploid race can be matched with those of the decaploid chromosome race. Four chromosome pairs that were recognized as marker chromosomes in octoploid and decaploid T. ponticum were almost identical. It is suggested that the two chromosome races of T. ponticum are segmental allopolyploids with genome designations J^jJ^jJ^eJ^e and J^jJ^jJ^jJ^eJ^e. Genome designations Jand J^e represent the same genome but with structural differentiation. Phylogenetic relationships between Thinopyrum species may be indicated by the presence or absence and type of marker chromosomes in the different species.     

Comparative analysis of rDNA location in five Neotropical gomphocerine grasshopper species

We report here, for the first time, the chromosome complement, number and location of the nucleolar organizer regions (NORs) revealed by silver staining (AgNO₃) and fluorescent in situ hybridization (FISH) in five Neotropical gomphocerine species: Rhammatocerus brasiliensis, R. brunneri, R. palustris, R. pictus and Amblytropidia sp. The objective of this study was to summarize available data and propose a model of chromosome evolution in Neotropical gomphocerines. All five species studied showed chromosome numbers consisting of 2n = 23,X0 in males and 2n = 24,XX in females. Amblytropidia sp. was the only species showing a bivalent (M₈) with megameric behavior during meiosis. The rDNA sites were restricted to autosomal pairs, i.e. the pericentromeric region of the S₉ chromosome, the consensus NOR location in all five species. R. brasiliensis was the only species showing additional NORs on M₄ and M₆ pairs which, likewise the S₉ NOR, were active in all cells analyzed. Comparison of these results with those reported previously in Palearctic gomphocerine species suggests higher resemblance of Neotropical species with the Old World species also possessing 23/24 chromosomes. Evolutionary mechanisms responsible for the observed interspecific variation in NOR location in this group are discussed.     

赤链蛇染色体组型、C型和Ag—NORs的研究

以骨髓细胞为材料研究赤链蛇的染色体,结果表明该物种2n=46,由8对大型的和15对微小的染色体组成,AF＝50。性染色体的大小介于3号和4号之间,为ZW;8大型染色体均显示着丝粒C带,1－6号还显示浅染端粒C带。W染色体为整条C带阳性,该物种一对NOR位于7号染色体近着丝粒区。不同地理分布群赤链蛇核型可能经历过Z与W染色体不等交换。     

Cytogenetic localization of genetic markers on porcine chromosome 7q

Four microsatellite markers ( S0078, SWR1210, SW732, and SW304 ) taken from the linkage map of porcine chromosome 7 were assigned to the cytogenetic map of pig chromosome 7 by fluorescence in situ hybridization (FISH) analysis of selected yeast artificial chromosomes (YACs). These four new polymorphic cytogenetic markers provide additional anchor points for integrating the linkage and cytogenetic maps of chromosomal region 7q.     

植物细胞遗传图及其应用

细胞遗传图（cytogenetic map）综合了来自遗传图（genetic map）和细胞学图（cytological map）两方面的信息,它既能反映基因或DNA标记之间在染色体上的真实距离,又能显示它们与染色体的细胞学结构间确切的位置关系。构建植物细胞遗传图的宗旨是将遗传图上的诸多标记与其在染色体的具体位置联系起来。目前主要有两种方法用于细胞遗传图的构建。较广泛使用的一种方法是借助染色体断点来确定遗传标记在染色体上的位置,另一种方法是利用荧光原位杂交（FISH）直接把DNA序列定位到染色体上。此外,利用RN-cM图也可以把遗传标记定位于粗线期染色体。从细胞遗传图可以看出,染色体两臂的远端有较高的基因密度和重组频率。细胞遗传图在比较近缘植物基因组的同线性、揭示植物的进化关系、研究基因定位克隆等方面都有重要意义.     

鹿科麂属动物基因组演化研究进展

鹿科麂属(Muntiacus, Cervidae)在近两三百万年内经历了快速物种辐射, 但其物种间核型差异巨大. 5个现生种核型数据显示, 该类群染色体数目范围从小麂(Muntiacus reevesi)的46条到赤麂(M. muntjak vaginalis)的6条. 该类群的基因组在较短时间内发生了快速演化, 使其成为进化生物学研究的理想材料. 40多年来, 技术的革新使该领域的研究不断深入, 染色体重排的类型、推动重排的分子机制及物种间的核型演化历程逐渐被阐释. 而且, 研究中发现, 雄性黑麂(M. crinifrons)1p+4染色体的演化途径与哺乳动物Y染色体的演化历程相似, 可成为哺乳动物性染色体演化研究的珍贵模型. 有关麂属动物基因组演化依然有许多问题等待更加全面、深入的探讨. 本文总结了该领域研究进展, 并对未来研究热点进行了展望.     

大蹄蝠的核型分析

研究了大蹄蝠的核型、C-带和Ag-NORs。大蹄蝠的染色体数目是2n=32,NF=60,No.8染色体上有一明显的次缢痕,大蹄蝠有丰富的结构异染色质,主要以着丝粒带的形式存在;且有若干对染色体部分或全部异染色质化;一对Ag-NORs稳定地出现于No.8染色体。     

Loss of nucleolar organizer regions during chromosomal evolution in the South American cricetid Graomys griseoflavus

Graomys griseoflavus is a South American phyllotine rodent having a remarkable Robertsonian polymorphism which may have produced reproductive isolation between 2n=42–41 and 2n=38–34 karyomorphs. Analysis of nucleolar organizer region (NOR) locations both by silver staining (Ag-NOR) and in situ hybridization revealed that 2n=42 individuals exhibit highly variable Ag-NOR patterns, while specimens of the 2n=38–34 karyomorphic group showed a single Ag-NOR pattern. The latter animals underwent two NOR deletions in reference to the 2n=42 karyomorphs, one of which would be the consequence of a Robertsonian fusion and the other would be produced by the unequal crossing-over mechanism. The differential NOR homogenization supports the hypothesis that G. griseoflavus karyomorphs are evolving separately towards the acquisition of separate species status.     

NOR polymorphism in the Iberian species Chondrostoma lusitanicum (Pisces: Cyprinidae) – re-examination by FISH

Chromosomal polymorphism regarding the number of chromosomal NOR sites in the cyprinid fish Chondrostoma lusitanicum reported previously (Rodrigues & Collares-Pereira, 1996) was re-examined using fluorescence in situ hybridization (FISH) with a ribosomal DNA (rDNA) probe. All positive CMA3-bands contained ribosomal DNA documented by either two or four FISH positive signals in the respective karyotypes. This polymorphism suggests the occurrence of structural rearrangements of translocation type in rDNA region from one ancestral NOR-bearing chromosome pair ubiquitous among leuciscine cyprinid fishes to another pair. The absence of individuals heterozygous for this polymorphism is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chromosome characterization and variability in some Iridaceae from Northeastern Brazil

The chromosomes of 15 species of Iridaceae of the genera Alophia, Cipura, Eleutherine, Neomarica and Trimezia (subfamily Iridoideae) were examined after conventional Giemsa staining. The karyotypes of Alophia drummondii (2n = 14+1B, 28, 42 and 56), Cipura paludosa (2n = 14), C. xanthomelas (2n = 28) and Eleutherine bulbosa (2n = 12) were asymmetric; Neomarica candida, N. caerulea, N. humilis, N. glauca, N. gracilis, N. northiana and Neomarica sp. (2n = 18); N. cf. paradoxa (2n = 28), Trimezia fosteriana (2n = 52), T. martinicensis (2n = 54) and T. connata (2n = 82) were all generally symmetric. New diploid numbers of 2n = 56 for Alophia drummondii, 2n = 18 for N. candida, N. humilis, N. glauca, and N. gracilis, 2n = 28 for N. cf. paradoxa, and 2n = 82 for T. connata are reported. The karyotypic evolution of the studied species is discussed.