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741.
Grishanin AK Rasch EM Dodson SI Wyngaard GA 《Evolution; international journal of organic evolution》2006,60(2):247-256
Collectively, populations of Acanthocyclops vernalis, a species complex of freshwater copepods, are remarkably similar as to morphology and DNA content, despite variability in chromosome number. Reproductive isolation had been reported among some populations, but with each new investigation the species boundaries and factors that may influence them appeared less clear. To clarify the pattern of biological species within this group of populations, we adopted a comprehensive approach and examined patterns of reproductive isolation in populations for which morphology, chromosome number, DNA content, and 18S rDNA sequences are known. In this study we established nine isofemale lines from four sites in Wisconsin and performed 266 crosses. Crosses within and among these lines were used to relate the degree of reproductive isolation to chromosome differences and to construct a model to explain the origin and maintenance of chromosome number variability. Different gametic and somatic chromosome numbers were observed among specimens within some isofemale lines. In a few cases, gametes with different haploid numbers were produced by a single female. Matings within isofemale lines always produced at least some reproductively successful replicate crosses (produced viable, fertile offspring). Crosses between lines from the same site showed reduced success relative to within-line crosses. Crosses between populations from distant sites showed limited genetic compatibility, producing viable, fertile F1 offspring but infertile F2 adults. One cross between lines with different chromosome numbers (one with 2n = 8 and one with 2n = 10) produced fertile viable offspring, which reproduced for at least 60 generations. These hybrids had either eight or nine chromosomes in the third generation of inbreeding, and eight chromosomes after 20 generations. These hybrids also had reduced nuclear DNA contents at the third generation, a level that persisted through the 20th generation. Successful backcrosses between some hybrids and their parental lines further demonstrated the potential for genetic compatibility among forms with different chromosome numbers. We propose a model in which alterations due to Robertsonian fusions, translocations, and/or loss of chromosomal fragments generate heritable variation, only some of which leads to reproductive isolation. Hence, some of the criteria traditionally used to recognize species boundaries in animals (morphology, DNA content, chromosome number) may not apply to this species complex. 相似文献
742.
743.
Identification of microRNAs from different tissues of chicken embryo and adult chicken 总被引:1,自引:0,他引:1
We report for the first time the identification of 25 microRNAs from tissues originating from chicken embryo and adult chicken. Most of the cloned microRNAs are expressed in both adult chickens and chicken embryos. Fourteen were identified without any prior prediction. One microRNA, miR-757, is thought to be chicken-specific. Three of the microRNAs appear to be extremely tissue specific. 相似文献
744.
745.
Sphingolipids function as bioactive mediators of different cellular processes, mostly proliferation, survival, differentiation and apoptosis, besides being structural components of cellular membranes. Involvement of sphingolipid metabolism in cancerogenesis was demonstrated in solid tumors as well as in hematological malignancies. Herein, we describe the main biological and clinical aspects of leukemias and summarize data regarding sphingolipids as mediators of apoptosis triggered in response to anti-leukemic agents and synthetic analogs as inducers of cell death as well. We also report the contribution of molecules that modulate sphingolipid metabolism to development of encouraging strategies for leukemia treatment. Finally we address how deregulation of sphingolipid metabolism is associated to occurrence of therapy resistance both in vitro and in vivo. Sphingolipids can be considered promising therapeutic tools alone or in combination with other compounds, as well as valid targets in the attempt to eradicate leukemia and overcome drug resistance. 相似文献
746.
Expression of Robo receptor molecules is important for axon guidance across the midline of the mammalian central nervous system. Here we describe novel isoform a of human ROBO2, which is initially strongly expressed in the fetal human brain but thereafter only weakly expressed in adult brain and a few other tissues. The known isoform b of ROBO2 shows a more or less ubiquitous expression pattern, suggesting diverse functional roles. The genomic structure and distinct expression patterns of Robo2a and Robo2b have been conserved in the mouse, but in contrast to human ROBO2a mouse Robo2a is also abundant in adult brain. Exons 1 and 2 of human ROBO2a lie in an inherently unstable DNA segment at human chromosome 3p12.3 that is associated with segmental duplications, independent chromosome rearrangements during primate evolution, and homozygous deletion and loss of heterozygosity in various human cancers. The 5' end of mouse Robo2a lies in a <150-kb DNA segment of break in synteny between mouse chromosome 16C3.1 and the human genome. 相似文献
747.
Automatic classification within families of transposable elements: Application to the mariner Family
Jacques-Deric Rouault Nathalie Casse Benoît Chénais Aurélie Hua-Van Jonathan Filée Pierre Capy 《Gene》2009
The higher levels of the classification of transposable elements (TEs) from Classes to Superfamilies or Families, is regularly updated, but the lower levels (below the Family) have received little investigation. In particular, this applies to the Families that include a large number of copies. In this article we propose an automatic classification of DNA sequences. This procedure is based on an aggregation process using a pairwise matrix of distances, allowing us to define several groups characterized by a sphere with a central sequence and a radius. This method was tested on the mariner Family, because this is probably one of the most extensively studied Families. Several Subfamilies had already been defined from phylogenetic analyses based on multiple alignments of complete or partial amino-acid sequences of the transposase. The classification obtained here from DNA sequences of 935 items matches the phylogenies of the transposase. The rate of error from a posteriori re-assignment is relatively low. 相似文献
748.
Trivedi PJ Patel PS Brahmbhatt MM Patel BP Gajjar SB Dalal EN Shukla SN Shah PM Bakshi SR 《Indian journal of human genetics》2009,15(3):137-139
We report here two cases of trisomy 13 in acute myeloid leukemia M1 subtype. short-term unstimulated bone marrow and peripheral blood lymphocyte culture showed 47, XY, +13 in all metaphase plates and trisomy 13 was confirmed with whole chromosome paint probes. Trisomy 13 in AML-M1 is a rare numerical abnormality. This is the first Indian report of sole trisomy 13 in AML-M1. Here, we present two cases of elder male patients, which may constitute a distinct subtype. 相似文献
749.
对报春花科(Primulaceae)报春花属(Primula)灯台报春组植物Section Proliferoe的7种报春进行了细胞学研究,其中腾冲灯台报春和川东灯台报春的核型分析为首次报道,结合已报道的灯台报春组其它植物的细胞学资料进行统计分析,结果表明灯台报春组植物在染色体基数、染色体形态、着丝点位置及染色体对称性上都具有很高的一致性,在灯台报春组有核型记录的种类中,其核型都属于Stebbins的2A型或2B型,核型差异很小,染色体基数均为x=11,推测其可能与报春花属中具有相同染色体基数的组亲缘关系更近。结合已发表的灯台报春组植物的细胞学资料及它们的形态特征,对其系统演化关系进行了比较分析,以期对该组的系统学及演化关系提供一些证据。 相似文献
750.
B. Hübner H. Strickfaden S. Müller M. Cremer T. Cremer 《European biophysics journal : EBJ》2009,38(6):729-747
Chromosome shattering has been described as a special form of mitotic catastrophe, which occurs in cells with unrepaired DNA
damage. The shattered chromosome phenotype was detected after application of a methanol/acetic acid (MAA) fixation protocol
routinely used for the preparation of metaphase spreads. The corresponding phenotype in the living cell and the mechanism
leading to this mitotic catastrophe have remained speculative so far. In the present study, we used V79 Chinese hamster cells,
stably transfected with histone H2BmRFP for live-cell observations, and induced generalized chromosome shattering (GCS) by
the synergistic effect of UV irradiation and caffeine posttreatment. We demonstrate that GCS can be derived from abnormal
mitotic cells with a parachute-like chromatin configuration (PALCC) consisting of a bulky chromatin mass and extended chromatin
fibers that tether centromeres at a remote, yet normally shaped spindle apparatus. This result hints at a chromosome condensation
failure, yielding a “shattered” chromosome complement after MAA fixation. Live mitotic cells with PALCCs proceeded to interphase
within a period similar to normal mitotic cells but did not divide. Instead they formed cells with highly abnormal nuclear
configurations subject to apoptosis after several hours. We propose a factor depletion model where a limited pool of proteins
is involved both in DNA repair and chromatin condensation. Chromosome condensation failure occurs when this pool becomes depleted.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This article has been submitted as a contribution to the festschrift entitled “Uncovering cellular sub-structures by light
microscopy” in honour of Professor Cremer’s 65th birthday. 相似文献