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Results for “karyotype evolution”

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PubMed2006

Chromosomal mapping of the major and minor ribosomal genes, (GATA)n and (TTAGGG)n by one-color and double-color FISH in the toadfish Halobatrachus didactylus (Teleostei: Batrachoididae).

The karyotype of Halobatrachus didactylus presents 46 chromosomes, composed of eight metacentric, 18 submetacentric, four subtelocentric, and 16 acrocentric chromosomes. The results of FISH showed that the major ribosomal genes were located in the terminal position of the short arm of a large submetacentric chromosome. They also showed a high variation in the hybridization signals. The products of amplification of 5S rDNA produced bands of about 420 pb. The PCR labeled products showed hybridization signals in the subcentromeric position of the long arm of a submetacentric chromosome of medium size. Double-color FISH indicated that the two ribosomal families are not co-located since they hybridized in different chromosomal pairs. Telomeres of all the chromosomes hybridized with the (TTAGGG)n probe. The GATA probe displayed a strong signal in the long arm of a submetacentric chromosome of medium size, in the subcentromeric position. The double-color FISH showed that the microsatellite GATA and the 5S rDNA gene are located in different chromosomal pairs. The majority presence of GATA probes in one pair of chromosomes is unusual and considering its distribution through different taxa it could be due to evolutionary mechanisms of heterochromatine accumulation, leading to the formation of differentiated sex chromosomes.

Animals↗
PubMed1994

Chromosomal speciation and adaptive radiation of mole rats in Asia Minor correlated with increased ecological stress.

The evolutionary forces causing chromosomal speciation and adaptation are still enigmatic. Here we tested the Israel evolutionary model of positive association of diploid chromosome number (2n) and genetic diversity with aridity stress in subterranean mole rats, on a 30-times-larger scale in Asia Minor. We analyzed both karyotype and allozyme diversity across Turkey, based on 37 allozymic loci in 20 localities of the Spalax leucodon and 4 localities of the Spalax ehrenbergi superspecies. We found extensive chromosomal speciation in S. leucodon (2n = 38, 40, 50, 54, 60, and 62) and in S. ehrenbergi (2n = 52, 56, and 58), presumably representing from 14 to > 20 additional biological species. Genetic diversity indices were low, but, like the chromosome number (2n), positively correlated with aridity stress, increasing centripetally from the periphery toward geologically young, arid, and climatically unpredictable central Anatolia. Nei's genetic distance D across all populations averaged 0.174 (range 0.002-0.422), supporting, combined with 2n and ecogeography, the biological species status of most tested populations. Chromosome evolution is the basis of speciation and adaptation in Spalax; it provides both postmating reproductive isolation, as well as higher levels of recombination with increased 2n. A mathematical model shows that a Robertsonian fission of a single metacentric considerably increases haplotype diversity. This haplotype diversity may contribute to population adaptation to climatic stress and ecological unpredictability in space and time. The increase in diversity corroborates the nichewidth genetic-variation hypothesis.

Animals↗
PubMed1998

Jumping translocations of chromosome 1q in multiple myeloma: evidence for a mechanism involving decondensation of pericentromeric heterochromatin.

Karyotypes in multiple myeloma (MM) are complex and exhibit numerous structural and numerical aberrations. The largest subset of structural chromosome anomalies in clinical specimens and cell lines involves aberrations of chromosome 1. Unbalanced translocations and duplications involving all or part of the whole long arm of chromosome 1 presumably occur as secondary aberrations and are associated with tumor progression and advanced disease. Unfortunately, cytogenetic evidence is scarce as to how these unstable whole-arm rearrangements may take place. We report nonrandom, unbalanced whole-arm translocations of 1q in the cytogenetic evolution of patients with aggressive MM. Whole-arm or "jumping translocations" of 1q were found in 36 of 158 successive patients with abnormal karyotypes. Recurring whole-arm translocations of 1q involved chromosomes 5,8,12,14,15,16,17,19,21, and 22. A newly delineated breakpoint present in three patients involved a whole-arm translocation of 1q to band 5q15. Three recurrent translocations of 1q10 to the short arms of different acrocentric chromosomes have also been identified, including three patients with der(15)t(1;15)(q10;p10) and two patients each with der(21)t(1;21)(q10;p13) and der(22)t(1;22) (q10;p10). Whole-arm translocations of 1q10 to telomeric regions of nonacrocentric chromosomes included der(12)t(1;12) (q10;q24.3) and der(19)t(1;19)(q10;q13.4) in three and two patients, respectively. Recurrent whole-arm translocations of 1q to centromeric regions included der(16)t(1;16)(q10;q10) and der(19)t(1;19)(q10;p10). The mechanisms involved in the 1q instability in MM may be associated with highly decondensed pericentromeric heterochromatin, which may permit recombination and formation of unstable translocations of chromosome 1q. The clonal evolution of cells with extra copies of 1q suggests that this aberration directly or indirectly provides a proliferative advantage.

Centromere↗
PubMed1999

Quantitative chromosome map of the polyploid Saccharum spontaneum by multicolor fluorescence in situ hybridization and imaging methods.

Somatic chromosomes of a wild relative of sugarcane (Saccharum spontaneum L.) anther culture-derived clone (AP 85-361, 2n = 32) were identified and characterized by computer-aided imaging technology and molecular cytological methods. The presence of four satellite chromosomes and four nearly identical chromosome sets suggests that the clone is a tetrahaploid with the basic number x = 8. A quantitative chromosome map, or idiogram, was developed using image analysis of the condensation pattern (CP) at the prometaphase stage of somatic chromosomes. The 45S and 5S ribosomal RNA gene (rDNA) loci were simultaneously visualized by multi-color fluorescence in situ hybridization (McFISH) and precisely localized to the regions of 3p3.1 and 6q1.3 on the idiogram. The simultaneous visualization of two sets of four ribosomal RNA genes confirms tetraploidy of this clone. This conclusion is consistent with results of molecular marker mapping. The quantitative chromosome map produced will become the foundation for genome analyses based on chromosome identity and structure. Previously impossible identification of small chromosomes and untestable hypotheses about the polyploid nature of plants can now be settled with these two approaches of quantitative karyotyping and FISH.

Chromosomes↗
PubMed2003

High-rate evolution of Saccharomyces sensu lato chromosomes.

Forty isolates belonging to the Saccharomyces sensu lato complex were analyzed for one nuclear and two mitochondrial sequences, and for their karyotypes. These data are useful for description and definition of yeast species based on the phylogenetic species concept. The deduced phylogenetic relationships among isolates based on the nuclear and mitochondrial sequences were usually similar, suggesting that horizontal transfer/introgression has not been frequent. The highest degree of polymorphism was observed at the chromosome level. Even isolates which had identical nuclear and mitochondrial sequences often exhibited variation in the number and size of their chromosomes. Apparently, yeast chromosomes have been frequently reshaped and therefore also the position of genes has been dynamic during the evolutionary history of yeasts.

Base Sequence↗
PubMed1989

Acute transformation of chronic large granular lymphocyte leukemia associated with additional chromosome abnormality.

A patient with large granular lymphocyte (LGL) leukemia that transformed into an acute or aggressive form after 20 months of the chronic phase is reported. The patient's leukemic cells were mature, medium-sized lymphocytes with sparse azurophil granules and the surface phenotypes of the cells were CD2+, CD3-, CD11+, and CD16+. Molecular analysis showed a germ line configuration in both T-cell receptor beta-chain genes and T-cell receptor tau-chain genes. A clonal anomaly of chromosome (trisomy 8) was demonstrated in peripheral blood cells. LGL after acute transformation of the disease displayed large blastic morphology with prominent nucleoli, intense basophilic cytoplasm, and numerous granules. Karyotypic analysis demonstrated a mosaic of trisomy 8 and trisomy 8 with an additional marker chromosome. Thus, transformation of chronic LGL leukemia into an acute or aggressive form in this patient was associated with morphologic and karyotypic changes of the leukemic cells. Patients with a stable form of chronic LGL leukemia should be examined carefully for the possible acute crisis associated with a clonal evolution.

Adult↗
PubMed1993

Temperature related fertility selection on body size and the sex-ratio gene arrangement in Drosophila pseudoobscura.

We measured temperature-dependent fertility selection on body size in Drosophila pseudoobscura in the laboratory. One hundred single females of each of the three karyotypes involving the 'sex-ratio' (SR) and the standard (ST) gene arrangement on the sex chromosome laid eggs at either 18 or 24 degrees C. The experiment addressed the following hypotheses: (a) Fertility selection on body size is weaker at the higher temperature, explaining in part why genetically smaller flies appear to evolve in populations at warmer localities. (b) Homokaryotypic SR females are less fecund than homokaryotypic ST females, possibly mediated by the effect of body size on fertility, explaining the low frequencies of SR despite its strong advantage due to meiotic drive. The data were also expected to shed light on a mechanism for the evolution of plasticity of body size through fertility selection in environments with an unpredictable temperature regime. Hypothesis (a) was clearly refuted because phenotypically larger ST females had an even larger fertility surplus at the higher temperature and, more importantly, the genetic correlation between fertility and body size disappeared at the lower temperature. As to (b), we found that temperature affects fertility directly and indirectly through body size such that ST and SR females were about equally fecund at both temperatures, although different in size and size-adjusted fertility. We observed heterosis for both size and fertility, which might stabilize the polymorphism in nature. The reaction norms of body size to the temperature difference were steeper for ST females than for SR females, implying that fertility selection could change phenotypic plasticity of body size in a population. Selection on body size depended not only on the temperature, but also on the karyotypes, suggesting that models of phenotype evolution using purely phenotypic fitness functions may often be inadequate.

Animals↗
PubMed2002

The phylogeny of howler monkeys (Alouatta, Platyrrhini): reconstruction by multicolor cross-species chromosome painting.

We performed multidirectional chromosome painting in a comparative cytogenetic study of the three howler monkey species Alouatta fusca, A. caraya and A. seniculus macconnelli (Atelinae, Platyrrhini) in order to reconstruct phylogenetic relationships within this genus. Comparative genome maps between these species were established by multicolor fluorescence in-situ hybridization (FISH) employing human, Saguinus oedipus and Lagothrix lagothricha chromosome-specific probes. The three species included in this study and previously analyzed howler monkey species were subjected to a phylogenetic analysis on the basis of a data matrix comprised of 98 discrete molecular cytogenetic characters. The results revealed that howler monkeys represent the genus with the most extensive karyotype diversity within Platyrrhini so far analyzed with high levels of intraspecific chromosomal variability. Two different multiple sex chromosome systems were identified. The phylogenetic analysis indicated that Alouatta is a monophyletic clade which can be derived from a proposed ancestral Atelinae karyotype of 2n = 62 chromosomes by a chromosome fusion, a fission, a Y-autosomal translocation and a pericentric inversion. Following these suggestions, the genus Alouatta can be divided into two distinct species groups: the first includes A. caraya and A. belzebul, the second A. s. macconnelli, A. sara, A. s. arctoidea and A. fusca.

Alouatta↗
PubMed2001

Cytogenetic findings and their clinical relevance in myelofibrosis with myeloid metaplasia.

The prognostic significance of bone marrow cytogenetic lesions in myelofibrosis with myeloid metaplasia (MMM) was investigated in a retrospective series of 165 patients. An abnormal karyotype was demonstrated in 57% of patients. At diagnosis (n = 92), 48% of the patients had detectable cytogenetic abnormalities, and clonal evolution was frequently demonstrated in sequential studies. More than 90% of the anomalies were represented by 20q-, 13q-, +8, +9, 12p-, and abnormalities of chromosomes 1 and 7. Of these, 20q-, 13q- and +8 were the most frequent sole abnormalities, each occurring in 15-25% of the abnormal cases. Trisomy 9 and abnormalities of chromosomes 1 and 7 were equally prevalent but were usually associated with additional cytogenetic lesions. Chromosome 5 abnormalities were infrequent but were over-represented in the group of patients exposed to genotoxic therapy. In a multivariate analysis that incorporated other clinical and laboratory variables, the presence of an abnormal karyotype did not carry an adverse prognosis. Instead, +8, 12p-, advanced age and anaemia were independent prognostic determinants of inferior survival. In particular, survival was not adversely affected by the presence of either 20q- or 13q-.

Adult↗
PubMed1997

Molecular identification of sympatric chromosomal forms of Anopheles gambiae and further evidence of their reproductive isolation.

Three chromosomal forms of Anopheles gambiae s.s., designated as Bamako, Mopti and Savanna, were studied for diagnostic PCR assays based on the analysis of the X-linked ribosomal DNA (rDNA). The study was performed on a 1.3 kb fragment containing part of the 28S coding region and part of the intergenic spacer region. The amplified material was cut with fourteen restriction enzymes to detect Restriction Fragment Length Polymorphisms (RFLPs). The enzymes Tru9I and HhaI produced patterns of DNA bands which differentiated Mopti from Savanna and Bamako; moreover, a distinct 'hybrid' pattern was recognized in the F1 female progeny from the cross of Mopti with either one of the other two chromosomal forms. The diagnostic significance of the PCR-RFLP assay was verified on 203 karyotyped females from field samples collected in two villages in Mali and one village in Burkina Faso. Agreement was observed between the chromosomal and the molecular identifications. No 'hybrid' molecular patterns were detected even among carriers of rare heterokaryotypes hypothetically produced by crosses between Mopti and Savanna. The results confirm previous observations indicating barriers to gene flow within An. gambiae s.s. and supporting the specific status of the taxonomic units proposed on cytogenetic ground.

Animals↗
PubMed2004

Structure and evolution of B chromosomes in amphibians.

B chromosomes are known from 26 species of salamanders and frogs, equivalent to about 2% of amphibian species that have been karyotyped. In most cases, the structure of amphibian B chromosomes has not been extensively investigated. The exceptions are the B chromosomes of Hochstetter's frog, Leiopelma hochstetteri, from New Zealand, and the Coastal Giant salamander, Dicamptodon tenebrosus, from North America. Dicamptodon tenebrosus carries from 0 to 10 non-heterochromatic, telocentric B chromosomes per individual, averaging 0 to 3.4 B chromosomes per individual in populations throughout its extensive range. The B chromosomes of L. hochstetteri occur in frequencies averaging from 0 to 11.4 per individual in different populations, with a known maximum of 15 B chromosomes. Amphibian B chromosomes vary in size, heterochromatin, occurrence and frequency. They are commensurate in size and structure with the rest of the A set of chromosomes of the same species in which they occur. The B chromosomes are at least partly composed of repetitive DNA sequences which exist in numerous copies throughout the autosomes, in conformity to an hypothesis of intraspecific B chromosome origins.

Amphibians↗
PubMed2002

Chromosome painting refines the history of genome evolution in hares and rabbits (order Lagomorpha).

Fluorescence in situ hybridization (FISH) was used to define homologous segments among representatives of 7 of the 11 recognized leporid genera. Chromosome painting using 22 rabbit chromosome-specific paints derived from flow-sorted chromosomes revealed that at least 18 fusions and six fissions differentiate the extant karyotypes from the presumed ancestral state (2n = 48). The riverine rabbit, Bunolagus monticularis, has the most derived karyotype, differing from the ancestor by seven fusions and five fissions, followed by Pronolagus rupestris, with four fusions and one fission. These findings are consistent with the proposed Palaeolaginae/Leporinae dichotomy in the lagomorphs. The molecular cytogenetic data allow for a refinement of the structural changes that have shaped genome evolution in this group of mammals and underscore the rapid radiation of the Leporidae suggested by mitochondrial DNA sequence data.

Animals↗
PubMed1981

A cytogenetic survey of 110 baboons (Papio cynocephalus).

A cytogenetic investigation of 110 adult baboons (Papio cynocephalus) captured in Kenya and sacrificed at the Institut Pasteur, Paris, showed the absence of anomalies, numerical or structural bearing on nonheterochromatic material; a polymorphism of the AgNOR-positive secondary constriction of chromosome 5 in 12% of the animals; a polymorphism of a secondary constriction of chromosome 7 in 2% of the animals; a fragile site of chromosome 6 in one animal. We believe that our data show that cytogenetic observations in present day primates probably reflect their chromosomal evolution.

Animals↗
PubMed1982

Evolutionary conservation of a common pattern of activity of nucleolus organizers during spermatogenesis in vertebrates.

The patterns of activity of the nucleolus organizer regions (NORs) in the spermatogeneses of ten species of all non-mammalian classes of vertebrates and one species of the cephalochordates were investigated with the silver (Ag)-staining technique. The Ag-stainability of the NORs is a measure of the transcriptional activity of the ribosomal RNA genes. In all species, there is a very similar pattern of NOR-activity in the various stages of spermatogenesis. The qualitative analysis of the Ag-stainability of the NORs was in very good agreement with the results obtained for mammals: Ag-stained NORs are detectable during the entire meiotic prophase up to the pachytene stage, completely absent in the meiotic metaphases I and II, and again demonstrable in early spermatid nuclei. The results confirm the occurrence of postmeiotic reactivation of the RNA genes. The preferential inhibition of rRNA synthesis by low doses of actinomycin D induced a rapid decline of the Ag-stainability of the postmeiotically reactivated NORs. The significance of the evolutionary conservation of the postmeiotic NOR-reactivation is discussed.

Animals↗
PubMed1986

The organization of the evolutionarily conserved GATA/GACA repeats in the mouse genome.

Simple repeated GATA and GACA sequences which were originally isolated from sex-specific snake satellite DNA have been found subsequently in all eukaryotes studied. The organization of these sequences within the mouse genome was investigated here by using synthetic oligonucleotide probes as a novel tool in comparison with conventional hybridization probes. Southern blot hybridization showed sex-specific patterns with both the (GATA)4 and (GACA)4 oligonucleotide probes, as previously described with conventional probes. The quantitative analysis of two mouse DNA phage libraries and of 25 isolated GATA-positive phage clones revealed intensive interspersion of GATA sequences with GACA, and with other repetitive and single-copy sequences. Ubiquitous interspersion and homogeneous genomic distribution of GATA and GACA sequences were confirmed by hybridization in situ of the oligonucleotide probes to metaphase chromosomes. The lengths of the GATA and GACA stretches were found to vary considerably in the individual phage clones. DNA inserts from 20 phages were assigned to autosomes and sex chromosomes and three genomic fragments were found to be confined to the Y chromosome. The organization of GATA and GACA sequences is discussed in the context of their evolutionary potential and possible conservation mechanisms.

Animals↗