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Results for “karyotype evolution”

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PubMed1985

G-banding evidence for a conserved complement in the Marsupialia.

G-banding data are presented for a wide range of Australian marsupial species and one South American species, all of which have 2n = 14. The chromosome banding pattern in each of these species is very similar. Variations between species can be explained by structural changes internal to individual chromosomes. This evidence favors the hypothesis of a conserved complement common to both Australian and American marsupials and underlies the dominant role of chromosome fission in the evolution of this group.

Animals↗
PubMed1997

Conservation of human vs. feline genome organization revealed by reciprocal chromosome painting.

We employed fluorescence in situ hybridization (FISH) with probes established by flow sorting metaphase chromosomes of the domestic cat (Felis cattus, 2n = 38) to "paint" homologous segments on human chromosomes and, reciprocally, using human chromosome paints on feline metaphase preparations. The results revealed, by direct microscopic observation, widespread conservation of genome organization between the two mammalian orders and confirmed 90% of the homologous genes mapped to both species. Fourteen of 23 human chomosomes were hybridized with single cat probes, and 9 of 19 cat chromosomes were entirely labeled by a single human probe. All other chromosomes were labeled with only two or, at most, three probes of the respective species. Y-chromosome probes gave no signals. Approximately 30 syntenic segments were identified, and the number of translocations could be estimated to be on the order of one new translocation per 10 million years in the phylogenetic lines leading to human and cat. Using the principle of maximum parsimony, the primitive vs. derived human chromosome segments were identified by comparison to the feline, cattle, and pig genomes, a first step in reconstructing the evolutionary heritage of the mammalian radiations. The results suggest that reciprocal chromosome painting will help reconstruct the history of genomic changes by determining the polarity of chromosomal rearrangements and establishing the ancestral karyotype for each principle branching point in mammalian evolution.

Animals↗
PubMed1999

Small B-cell lymphomas of the lymph nodes and spleen: practical insights to diagnosis and pathogenesis.

As defined in the proposed World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues, the small B-cell lymphomas include B-cell chronic lymphocytic leukemia / small lymphocytic lymphoma, mantle cell lymphoma, follicular lymphoma, marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type, nodal marginal zone lymphoma, lymphoplasmacytic lymphoma, and splenic marginal zone B-cell lymphoma. These neoplasms are recognized mostly on the basis of their histopathologic features, but ancillary studies are useful in confirming and sometimes making the diagnosis. Clinically, the small B-cell lymphomas of lymph nodes and spleen (but not those of MALT type) are usually disseminated at diagnosis and considered incurable. With the exception of mantle cell lymphoma, however, they are generally indolent. The small B-cell lymphomas are among the best examples of how malignant lymphomas can be related to the normal immune system. Although uncertainties exist, these lymphomas are generally considered the neoplastic equivalents of normal B-cell compartments. From a molecular perspective, mantle cell and follicular lymphomas are the best characterized. In both cases, there are characteristic chromosomal translocations involving the immunoglobulin heavy chain and the cyclin D1 or bcl-2 genes, respectively, that are probably followed by additional molecular events leading to overt neoplasia. Variable proportions of the small B-cell lymphomas undergo transformation that might be associated with abnormalities in tumor suppressor genes / cell cycle regulatory proteins. After a brief review of normal B-cell development, the major small B-cell lymphomas (except for those of MALT type) will be discussed in terms of their morphologic features, immunophenotype (including paraffin-section immunostaining), genotype, karyotype, and clinical features, including disease evolution.

Humans↗
PubMed2005

[Divergence patterns of banding sequences in different polytene chromosome arms reflect relatively independent evolution of different genome components].

Divergence patterns of the banding sequences from the chromosomal arms A, C, D, E, and F were compared in 63 species of the genus Chironomus. Evaluation of the number of breakpoints between the pairs of inverted banding sequences and the analysis of the lengths of the conserved segments in the chromosomal arms in the chironomid species examined showed that different arms evolved relatively independently and at different rates. No direct correlation between the arm length and the breakpoints number was observed. The length of the conservative segment was not fixed, but was arm-specific. Robustness and fidelity of the estimates of phylogenetic relationships between the species examined increased with the arm number, i.e., with the genome proportion included in the analysis.

Animals↗
PubMed2006

Genetic architecture of the cryptic species complex of Acanthocyclops vernalis (Crustacea: Copepoda). II. Crossbreeding experiments, cytogenetics, and a model of chromosomal evolution.

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.

Animals↗
PubMed1990

[Demonstration of BCR-ABL rearrangement in a patient with apparently Ph-negative chronic myeloid leukemia of 15 years' duration].

We have studied the haematologic cytogenetic and molecular features in a patient with Ph negative CML of 15 years of evolution. Cytogenetic analysis showed a normal karyotype in different studies. Molecular study showed rearrangement within bcr region. This gene fusion between c-abl oncogene and bcr gene is typical of the Ph chromosome. These results show the usefulness of performing a molecular study in those patients with Ph negative CML.

Adult↗
PubMed1990

[Repetitive DNA, chromosome polymorphism and speciation of gerbils].

Restriction analysis of DNA and differential staining of chromosomes in three species of the genus Meriones: M. tristrami. M. meridianus. M. inguiculatus was carried out. High extent of homology of the genomes under study was found at the molecular and chromosomal levels. Speciation of M. tristrami followed by numerous fissions of metacentric chromosomes is assumed to be connected with appearance of the short BspRI sequence. Possible mechanisms of the mammal genome evolution are discussed.

Animals↗