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Results for “karyotype evolution”

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PubMed1998

[Chromosome arrangements and cytogenetic differentiation of two species of African mice of the genus Mus (Rodentia, Muridae)].

Karyotypes of two African mouse species, Mus mahomet, 2n = 36, NFa = 34 (34A + XA + YA) and Mus sp. A, 2n = 34, NFa = 32 (32A + XA + YA), from five localities of the Bale Mountains National Park, Ethiopia, were analyzed. In both species all autosomes contained C-positive pericentromeric blocks. In M. mahomet, heterochromatin blocks of different chromosomes varied in size. In addition, the X chromosomes of both species contained a pericentromeric block and showed more intensive staining throughout the chromosome. The Y chromosome was two times larger in Mus sp. A than in M. mahomet and C-positive in both species. Comparative analysis of G-banding patterns revealed a similarity with respect to nine autosomes and the X chromosome. Autosome 1 of Mus sp. A was demonstrated to result from centromere-telomere fusion of two M. mahomet acrocentrics. The other five autosomes represent different linkage groups determining a specificity of the karyotypes. The karyotypes of M. mahomet and Mus sp. A were also compared with that of M. musculus. The evolution of M. mahomet and Mus sp. A karyotypes was shown to have involved structural rearrangements in 10 and 12 autosomes, respectively. The high karyological divergence confirmed molecular phylogenetic data. The cytogenetic differences T of M. musculus C from M. mahomet and Mus sp. A are high enough to different genera.

Animals↗
PubMed2004

Chromosomes of tuatara, Sphenodon, a chromosome heteromorphism and an archaic reptilian karyotype.

We examined karyotypes of the endemic New Zealand reptile genus Sphenodon (tuatara) from five populations, finding a karyotype unchanged for at least one million years. Animals karyotyped were from five geographically distinct populations, representing three groups, namely S. guntheri, S. punctatus (Cook Strait group), and S. punctatus (northeastern North Island group). All five populations have a diploid chromosome number of 2n = 36, consisting of 14 pairs of macrochromosomes and four pairs of microchromosomes. Chromosomal differences were not found between the five populations nor between female and male animals, except for one animal with a structural heteromorphism. Similarity between Sphenodon and Testudine karyotypes suggests an ancestral karyotype with a macrochromosome complement of 14 pairs and the ability to accumulate variable numbers of microchromosome pairs. Our research supports molecular phylogenies of the Reptilia.

Animals↗
PubMed1996

Report of a complex karyotype in recurrent metastatic fibrolamellar hepatocellular carcinoma and a review of hepatocellular carcinoma cytogenetics.

Metastatic fibrolamellar hepatocellular carcinoma (HCC) was detected in the abdominal lymph nodes of an adolescent male after resection of the primary tumor. No dividing cells were isolated from attempted cytogenetic studies of the primary tumor. However, cytogenetic analysis of lymph node metastases detected 9 and 12 months after partial hepatectomy revealed abnormal hypertriploid karyotypes, with a suggestion of clonal evolution: 62-92 < 3n >,XX, -Y, +3, +6, +6, +7, +7, +8, +10, +13, +15, +16, +20, -21, -22, +mar1 x 2, +mar[cp6]/46,XY[8] and 78 < 3n >,XX, -Y,der(1)t(1;1)(p36.1;q21), +4, +6, +6, +7, +7,i(8)(q10), +10, +15, +20, -21, -22, +mar1 x 2, +mar2[3]/46, XY[17], respectively. Karyotypes of this variant of HCC have not been reported previously. The cytogenetics of HCC are reviewed.

Adolescent↗
PubMed2001

Comparative cytogenetics of the African elephant (Loxodonta africana) and Asiatic elephant (Elephas maximus).

G- and C-banded karyotypes of the two extant species of the mammalian order Proboscidea are presented for the first time. Chromosome complements were 2n = 56 in both Loxodonta africana and Elephas maximus. Comparisons between the species demonstrated a high level of chromosome band homology, with 26 conserved autosomal pairs. The normal diploid karyotype of L. africana had 25 acrocentric/telocentric and two metacentric/submetacentric autosomal pairs. E. maximus differed by having one less acrocentric and one additional submetacentric pair due to either a heterochromatic arm addition or deletion involving autosomal pair 27. Several acrocentric autosomes of L. africana exhibited small short arms that were absent in homologous chromosomes of E. maximus. The X chromosomes in both species were large submetacentric elements and were homologous. However, the small acrocentric Y chromosomes differed; in E. maximus it was slightly larger and had more distinct G-bands than its counterpart in L. africana. Extant Elephantidae appear to be relatively conservative in their rates of chromosomal change compared to some other mammalian families. The high-quality banded karyotypes presented here should prove useful as references in future chromosome analyses of elephant populations and in comparative cytogenetic studies with other ungulate orders.

Africa↗
PubMed1983

The karyotype of Galago crassicaudatus is ancestral for lorisiforms.

The karyotype, comprised of 62 chromosomes, of Galago crassicaudatus is described. It is compared to the karyotype of Galago senegalensis and to that of the presumed common ancestor to Lorisiforms, previously reconstructed. Most of the reconstructed chromosomes were found, unmodified, in G. crassicaudatus, strengthening the validity of the reconstruction.

Animals↗
PubMed2004

Detection of BCR/ABL fusion product in normoblasts in a case of chronic myelogenous leukemia.

Erythroblast phase of chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute erythroid leukemia are rare events. The distinction between these two entities is poorly defined. The World Health Organization (WHO) classification requires the presence of more than 50% of erythroblasts in the bone marrow for the diagnosis of both the erythroid/myeloid or pure erythroid subtypes of acute erythroid leukemia. However, in previous studies of erythroblast crisis CML, the percentage of erythroid series in the bone marrow is seldom mentioned and the direct relationship of the erythroblasts and the Philadelphia chromosome has never been established. We report a well-documented case of acute erythroid leukemia transformed from CML. The studies in morphology, immunohistochemistry, and flow cytometry fulfill the WHO criteria for the diagnosis of acute erythroid leukemia, and yet the complex karyotype containing Philadelphia chromosome indicates genetic evolution. Finally, the direct demonstration of the BCR/ABL fusion product by fluorescence in situ hybridization in the erythroblasts provides concrete evidence that the erythroblasts are part of the leukemic process and not an innocent bystander.

Erythroblasts↗
PubMed2004

Recombination drives the evolution of GC-content in the human genome.

Unraveling the evolutionary forces responsible for variations of neutral substitution patterns among taxa or along genomes is a major issue in the identification of functional sequence features. Mammalian genomes show large-scale regional variations of GC-content (the isochores), but the substitution processes at the origin of this structure are poorly understood. We have analyzed the pattern of neutral substitutions in 14.3 Mb of primate noncoding regions. We show that the GC-content toward which sequences are evolving is strongly correlated (r(2) = 0.61, P </= 2 10(-16)) with the rate of crossovers (notably in females). This demonstrates that recombination drives the evolution of base composition in human (probably via the process of biased gene conversion). The present substitution patterns are very different from what they had been in the past, resulting in a major modification of the isochore structure of our genome. This non-equilibrium situation suggests that changes of recombination rates occur relatively frequently during evolution, possibly as a consequence of karyotype rearrangements. These results have important implications for understanding the spatial and temporal variations of substitution processes in a broad range of sexual organisms, and for detecting the hallmarks of natural selection in DNA sequences.

Animals↗
PubMed1994

Genome evolution: between the nucleosome and the chromosome.

Intermediate between DNA sequences and broad patterns of karyotypic change there is a major gap in understanding genome structure and evolution. The gap is at the megabase level between genes and chromosomes. New methods for analyzing large DNA fragments cloned in yeast or bacterial vectors provide experimental access to genome evolution at the megabase level by enabling the assembly of megabase-size contiguous regions. Genome evolution at the megabase level can also be studied using high-resolution genetic maps. Rates and patterns of genome evolution in mammals (mouse versus humans) and Drosophila (D. virilis versus D. melanogaster) are compared and contrasted. Opportunities for research in genome evolution using the new technologies are enumerated and discussed.

Animals↗
PubMed2001

Polymorphism and polytypy for pericentric inversions in 38-chromosome Mastomys (Rodentia, Murinae) and possible taxonomic implications.

Chromosome banding analysis (R- and C-bands) of two 38-chromosome Mastomys specimens originating from the Ivory Coast and Uganda revealed different numbers of autosome arms (NFa), equal to 51 and 60, respectively. Comparison of their chromosome banding patterns with those of Mastomys specimens from the Sudan (NFa = 41) and Senegal (NFa = 51-54), studied previously, showed that variation of the NFa from 40 to 60 throughout the species distribution is the result of a pericentric inversion polymorphism involving 3-12 chromosome pairs. At the population level, this variation is much narrower and never results from more than two chromosome pairs involved in inversion polymorphism. Taking into account that the NFa values recorded to date form a well-defined discontinuous row, we presume that introgressive hybridization between populations differing from each other by 3-5 to 11-12 pericentric inversions is interrupted. From there, the hypothesis of the existence of at least three cryptic species (designated provisionally as MER-1, MER-2, and MER-3) within 38-chromosome Mastomys populations previously assigned to M. erythroleucus can be made. It looks likely that one of them, possessing a karyotype with an NFa = 50-56, is widely distributed throughout sub-Saharan Africa and includes karyotyped populations from Senegal, the Ivory Coast, Mali, Benin, Cameroon, Zaire, and the Sudan. The second species (MER-2) includes the specimens karyotyped (NFa = 40-41) from Chad and the Sudan. Finally, a third tentative species (MER-3) corresponds to specimens with NFa = 59-60 found in East Zaire and Uganda, as well as possibly Mali and Chad.

Animals↗
PubMed2006

Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae).

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, São Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.

Animals↗
PubMed2003

Karyotype variation in the South American aphid genus Neuquenaphis (Hemiptera, Aphididae, Neuquenaphidinae).

The endemic South American aphid genus Neuquenaphis (Hemiptera, Aphididae, Neuquenaphidinae) forms an important component of the phytophagous insect fauna associated with southern beeches, Nothofagus (Nothofagaceae), but has not previously been studied cytologically. As part of ongoing studies of the taxonomy, evolution and host relationships of this genus, the karyotypes of 12 species are described and illustrated. Species are mostly distinguishable by differences in number and/or relative lengths of chromosomes, with 2n (female) numbers ranging from 6 to 16. The taxonomic and evolutionary significance of the karyotype variation in this group are discussed.

Animals↗
PubMed1980

Evolution of cultured leukemic cell lines monitored by chromosomal and immunologic analysis.

We have investigated the karyotypes and markers of B lymphocyte differentiation in two leukemic cell lines, NALM-6-B and NALM-6-MI, both derived from a patient with non-T, non-B acute lymphoblastic leukemia. Both possess characteristics of thymus-independent, bursal-equivalent (B) lymphocytes. By means of immuno-fluorescence techniques, NALM-6-B was shown to possess 47% surface membrane immunoglobulin-positive (Slg+) cells, while NALM-6-MI is surface membrane immunoglobulin-negative (Slg-), but does possess cytoplasmic immunoglobulin M (ClgM+) in more than 90% of the cells. The Slg- ClgM+ phenotype, coupled with morphologic features, is consistent with NALM-6-MI being arrested at a stage early in B-lymphocyte differentiation (a "pre-B" cell). The predominant banded chromosome karyotype of NALM-6-B is pseudodiploid with a translocation of chromosomal material from the long arm of a chromosome 5 to the short arm of a chromosome 12 (5q-/12p+) and a marker Y chromosome. NALM-6-MI possesses the same marker Y chromosome and a deletion of the long arm of chromosome 5(5q-) since in most cells material missing from chromosome 5 does not appear on the short arm of chromosome 12. Within the limits of resolution available with the banding technique, no other karyotypic differences are observed in the two cell lines. The history of the two cell lines, the karyotypic analysis, and the pattern of immunoglobulin markers indicate the possible clonal evolution of NALM-6-MI from NALM-6-B and implicate a portion of the long arm of chromosome 5 in lymphoid differentiation of these leukemic cell lines.

Adult↗
PubMed1976

Karyotypic analysis and evidence of tetraploidy in the North American paddlefish, Polyodon spathula.

A model chromosome number of 120 was obtained for the ancient fish. Polyodon spathula (Pisces: Chondrostei). The karyotype consists of 48 macrochromosomes and 72 microchromosomes. The microchromosomes are like those found in certain other primitive fishes as well as in reptiles and birds. The possiblity that Polyodon is a species of tetraploid origin is strongly suggested by the fact that the 120 chromosomes are easily arranged into 30 groups of four homologs each. Evolutionary comparisons are made with other primitive fish groups.

Animals↗