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Results for “karyotype evolution”

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At least 1,531 records · Page 85Linked to original sources
PubMed2005

Mitochondrial phylogeny reveals differential modes of chromosomal evolution in the genus Tatera (Rodentia: Gerbillinae) in Africa.

The African gerbils of the genus Tatera are widespread and abundant throughout sub-Saharan Africa. There is still today a certain controversy concerning the taxonomy of these rodents and very few attempts have been made to assess their systematic relationships. The present paper introduces findings based on the partial sequences of cytochrome b (495 bp) and the 16S rRNA (469 bp) mitochondrial genes of six (T. robusta, T. nigricauda, T. vicina, T. leucogaster, T. valida, and T. kempi) species together with two additional taxa. We also report the karyotypes of T. vicina and T. leucogaster. We propose that T. vicina should be considered as a valid species and show the monophyly of the robusta species group, with the exclusion of T. leucogaster. Our results show there is a different chromosomal evolutionary pattern within the two major lineages, which is recognizable through molecular phylogenetics. One is characterized by karyotype stability and the other by a considerable number of chromosomal rearrangements. The lineage divergence coincides with the formation of the East African Rift. The processes that led to the origin of the East African species seem to be related to the subsequent climatic changes, which caused cyclic contraction and expansion of the savannah biomes. Furthermore, geological activities that characterized East Africa during Plio-Pleistocene may also have contributed to lineage divergence.

Africa↗
PubMed2004

Monosomy 7 in patients with aplastic anemia and paroxysmal nocturnal hemoglobinuria with evolution into acute myeloid leukemia.

We report two cases of Thai patients with aplastic anemia/paroxysmal nocturnal hemoglobinuria (AA/PNH) who subsequently developed acute myeloid leukemia (AML) at their terminal phase. Monosomy 7 was demonstrated upon karyotypic analysis of bone marrow in both cases at the time leukemia developed The first patient was a 25-year-old man diagnosed with AA at age 14, recovered from AA at age 15, developed PNH at age 21 and turned into AML at age 25. The second patient was a 27-year-old man diagnosed with PNH at age 22, developed severe AA at age 25 and turned into AML at age 27. This latter patient received anti-lymphocyte globulin when he developed severe AA but did not respond well whereas the first patient fully recovered from AA with anabolic hormone treatment. Time to diagnosis of AML in the patient who received immunosuppressive therapy was strikingly shorter than that who received conventional androgen therapy (2 years vs 11 years after AA, respectively). The presence of monosomy 7 in leukemic cells of both patients emphasizes its central role in the development of AML from AA/PNH. However, other factors such as choice of AA/PNH therapy and patients response may modulate the time to emergence of monosomy 7-carrying AML clone and frank leukemia. Further studies into the biologic and genetic mechanisms involved in the development of leukemic clone arising from AA/PNH should be explored.

Acute Disease↗
PubMed1975

Localization of rDNA and Giemsa-banded chromosome complement of white-handed gibbon, Hylobates lar.

A karyotype based on banding pattern and chromosome length is presented for the white-handed gibbon, Hylobates lar. Little homology with the banding patterns of the chromosomes of the other Hominoidea can be seen, confirming the early evolutionary separation of Hylobatidae and the other apes. Hybridization in situ with ribosomal RNA shows that the secondary constriction of a submetacentric chromosome (15) is the only site of the nucleolar organizer, as in the Cercopithecoidea. The correlation of polymorphic variation in size of this secondary constriction with grain density suggests differences in the number of gene copies per chromosome.

Animals↗
PubMed1991

Increased SOD1 enzymatic activity and gene modifications in orangutans: evolutionary implications.

Superoxide dismutase CuZn (SOD1) enzymatic activity was measured in five orangutans (Pongo pygmaeus, PPY) and compared to that of man, chimpanzee, and gorilla. It was found to be increased by a factor of two in one orangutan (Ralfina) and by a factor of 1.5 in the four others. In situ hybridization of the SOD1 cDNA human probe showed a heterozygous intra-chromosomal rearrangement of pair PPY XXI, possibly an insertion, in Ralfina. Southern blotting showed that the SOD1 gene is modified in the three orangutans that were investigated and that a further modification of the 5'-end of the gene had occurred in Ralfina. The evolutionary implications of these observations are discussed.

Animals↗
PubMed1977

Comparative cytogenetic and histologic studies on early malignant transformation in mesothelial tumors of the ovary.

Comparative cytogenetic and histologic studies on 18 mesothelial ovarian tumors revealed a normal chromosome complement in benign lesions, and the well-known cytogenetic pattern in cystadenocarcinomas. But all borderline tumors of the series evidenced an abnormal stem line and a more or less marked tendency to polyploidization. Serous papillary cystadenomas of this group showed in five out of six cases a stem line with the karyotype 47,XX+C10 (identified by Q-banding), present in both sides of bilateral lesions. It is evidenced that malignant change on the chromosomal level precedes histologically detectable features of malignancy. Histologic equivalents appeared, when the abnormal cell line was established. The initiation of malignant transformation therefore may be signalized by karyotype abnormalities before structural changes can be detected in the corresponding histologic specimens. The results discussed include the concepts of multicentric origin and clonal evolution of malignancy.

Cell Transformation, Neoplastic↗
PubMed1993

Lack of intratumoral heterogeneity in DNA ploidy pattern of hepatocellular carcinoma.

BACKGROUND: From biological and clinical perspectives, it is important to clarify tumor heterogeneity. This study was aimed to investigate whether or not intratumoral heterogeneity of DNA ploidy pattern exists in hepatocellular carcinoma (HCC). METHODS: Using fresh materials resected from 31 untreated patients, DNA ploidy was analyzed at different sites of the same HCC by means of flow cytometry. The tumor size ranged from 1.7 to 25.0 cm. RESULTS: There was no case in which euploid and aneuploid HCCs coexisted in the same tumor. The DNA ploidy pattern was euploid in 15 and aneuploid in 16 instances. Of 15 euploid tumors, the areas analyzed were all diploid in 12 and tetraploid in 2 but diploid/tetraploid in 1. Among 16 aneuploid tumors, the DNA indices (DI) at different sites were similar in 9, but apparently, different aneuploid subclones coexisted in 7 cases. The incidence of DI heterogeneity in aneuploid HCCs was similar between small (< 5 cm) and large (> or = 5 cm) tumors; 3 of 7 (42.9%) versus 4 of 9 (44.4%). CONCLUSIONS: It is assumed that euploid and aneuploid HCCs develop in their own ploidy pattern and that the evolution of aneuploid subpopulations from euploid HCC is rare, but new aneuploid subclones can evolve from aneuploid HCC due to increased instability of its karyotype.

Adult↗
PubMed1998

Isolated mild fetal pyelectasis detected by transvaginal sonography in advanced maternal age.

OBJECTIVE: To evaluate the importance and evolution of isolated, mild fetal pyelectasis, detected in early pregnancy by high-resolution transvaginal sonography, and to determine its association with abnormal fetal karyotypes. METHODS: Transvaginal scan at 11-16 weeks' gestation and transabdominal ultrasound examinations at the time of amniocentesis (16-18 weeks) were performed in 1093 pregnant women undergoing genetic amniocentesis because of advanced maternal age. In 795 cases, transabdominal scans were repeated at 22-24 weeks. Women were excluded if they had a spontaneous abortion, chose to terminate their pregnancy, or declined amniocentesis. Each patient was screened for fetal pyelectasis, defined as an increase in anteroposterior renal pelvic diameter, using cutoff values related to various stages of pregnancy. RESULTS: Isolated fetal pyelectasis was detected at the first ultrasound examination in 56 women (5.1%) in early pregnancy, in 32 (2.9%) at the time of amniocentesis, and in 23 (2.9%) at 22-24 weeks' gestation. Two fetuses with diagnoses of mild pyelectasis at the first transvaginal ultrasound demonstrated abnormal karyotypes at amniocentesis. In one case, the pyelectasis disappeared at 22-24 weeks' gestation. CONCLUSION: This retrospective study shows that pyelectasis is more frequently detectable by high-resolution transvaginal sonography in the first half of pregnancy than in the second half. When detected in early pregnancy, the finding is frequently transient and not associated with an increased risk of abnormal fetal karyotypes.

Adult↗
PubMed1999

ZOO-FISH analysis in a species of the order Chiroptera: Glossophaga soricina (Phyllostomidae).

Glossophaga soricina is a flower-visiting bat which lives in the neotropics. The diploid chromosome number is 2n = 32 with a fundamental number of autosomal arms, FN, of 60. G. soricina belongs to the Microchiroptera which have a lower diploid DNA content and a higher AT composition in their DNA compared with other mammals. By ZOO-FISH analysis with human chromosome-specific DNA probes, the human autosomes were found conserved in 41 segments. This is an arrangement similar to other mammals which have been analyzed. Several chromosomal associations already known from ZOO-FISH studies in other species were also present in G. soricina.

Animals↗
PubMed2000

Molecular cytogenetic dissection of human chromosomes 3 and 21 evolution.

Chromosome painting in placental mammalians illustrates that genome evolution is marked by chromosomal synteny conservation and that the association of chromosomes 3 and 21 may be the largest widely conserved syntenic block known for mammals. We studied intrachromosomal rearrangements of the syntenic block 3/21 by using probes derived from chromosomal subregions with a resolution of up to 10-15 Mbp. We demonstrate that the rearrangements visualized by chromosome painting, mostly translocations, are only a fraction of the actual chromosomal changes that have occurred during evolution. The ancestral segment order for both primates and carnivores is still found in some species in both orders. From the ancestral primate/carnivore condition an inversion is needed to derive the pig homolog, and a fission of chromosome 21 and a pericentric inversion is needed to derive the Bornean orangutan condition. Two overlapping inversions in the chromosome 3 homolog then would lead to the chromosome form found in humans and African apes. This reconstruction of the origin of human chromosome 3 contrasts with the generally accepted scenario derived from chromosome banding in which it was proposed that only one pericentric inversion was needed. From the ancestral form for Old World primates (now found in the Bornean orangutan) a pericentric inversion and centromere shift leads to the chromosome ancestral for all Old World monkeys. Intrachromosomal rearrangements, as shown here, make up a set of potentially plentiful and informative markers that can be used for phylogenetic reconstruction and a more refined comparative mapping of the genome.

Animals↗
PubMed2001

Molecular characterization and gene content of breakpoint boundaries in patients with neurofibromatosis type 1 with 17q11.2 microdeletions.

Homologous recombination between poorly characterized regions flanking the NF1 locus causes the constitutional loss of approximately 1.5 Mb from 17q11.2 covering > or =11 genes in 5%-20% of patients with neurofibromatosis type 1 (NF1). To elucidate the extent of microheterogeneity at the deletion boundaries, we used single-copy DNA fragments from the extreme ends of the deleted segment to perform FISH on metaphase chromosomes from eight patients with NF1 who had large deletions. In six patients, these probes were deleted, suggesting that breakage and fusions occurred within the adjacent highly homologous sequences. Reexamination of the deleted region revealed two novel functional genes FLJ12735 (AK022797) and KIAA0653-related (WI-12393 and AJ314647), the latter of which is located closest to the distal boundary and is partially duplicated. We defined the complete reading frames for these genes and two expressed-sequence tag (EST) clusters that were reported elsewhere and are associated with the markers SHGC-2390 and WI-9521. Hybrid cell lines carrying only the deleted chromosome 17 were generated from two patients and used to identify the fusion sequences by junction-specific PCRs. The proximal breakpoints were found between positions 125279 and 125479 in one patient and within 4 kb of position 143000 on BAC R-271K11 (AC005562) in three patients, and the distal breakpoints were found at the precise homologous position on R-640N20 (AC023278). The interstitial 17q11.2 microdeletion arises from unequal crossover between two highly homologous WI-12393-derived 60-kb duplicons separated by approximately 1.5 Mb. Since patients with the NF1 large-deletion syndrome have a significantly increased risk of neurofibroma development and mental retardation, hemizygosity for genes from the deleted region around the neurofibromin locus (CYTOR4, FLJ12735, FLJ22729, HSA272195 (centaurin-alpha2), NF1, OMGP, EVI2A, EVI2B, WI-9521, HSA272196, HCA66, KIAA0160, and WI-12393) may contribute to the severe phenotype of these patients.

Base Sequence↗
PubMed2005

The zebrafish gene map defines ancestral vertebrate chromosomes.

Genetic screens in zebrafish (Danio rerio) have identified mutations that define the roles of hundreds of essential vertebrate genes. Genetic maps can link mutant phenotype with gene sequence by providing candidate genes for mutations and polymorphic genetic markers useful in positional cloning projects. Here we report a zebrafish genetic map comprising 4073 polymorphic markers, with more than twice the number of coding sequences localized in previously reported zebrafish genetic maps. We use this map in comparative studies to identify numerous regions of synteny conserved among the genomes of zebrafish, Tetraodon, and human. In addition, we use our map to analyze gene duplication in the zebrafish and Tetraodon genomes. Current evidence suggests that a whole-genome duplication occurred in the teleost lineage after it split from the tetrapod lineage, and that only a subset of the duplicates have been retained in modern teleost genomes. It has been proposed that differential retention of duplicate genes may have facilitated the isolation of nascent species formed during the vast radiation of teleosts. We find that different duplicated genes have been retained in zebrafish and Tetraodon, although similar numbers of duplicates remain in both genomes. Finally, we use comparative mapping data to address the proposal that the common ancestor of vertebrates had a genome consisting of 12 chromosomes. In a three-way comparison between the genomes of zebrafish, Tetraodon, and human, our analysis delineates the gene content for 11 of these 12 proposed ancestral chromosomes.

Animals↗
PubMed2001

Unravelling the phylogeny of tetraploid Vicia amoena (Fabaceae) and its diploid relatives using chromosomal landmarks.

The chromosomal sites of 5S and 45S rDNA genes were revealed by fluorescence in situ hybridisation, and used as landmarks to resolve the ambiguous taxonomic status of the tetraploid Vicia amoena var. amoena (Fabaceae). Comparisons of the number and location of rDNA loci in V. amoena var. sericea, V. pseudorobus, V. dumetorum, V. pisiformis and V. cracca confirmed that V. amoena var sericea, or a closely related diploid, was a likely progenitor of the tetraploid. However, the tetraploid contains chromosomes bearing rDNA loci which are probably derived from another species, such as V. pseudorobus, suggesting that it is an allotetraploid and the product of an interspecific hybridisation event. This was corroborated by fluorescence in situ hybridisation with genomic DNA from V. amoena var sericea, which not only showed that the tetraploid contains more than one chromosome set, but also that its constituent sets have undergone considerable reorganisation.

China↗
PubMed2006

Phylogenetic reconstruction of Aegilops section Sitopsis and the evolution of tandem repeats in the diploids and derived wheat polyploids.

The evolution of 2 tandemly repeated sequences Spelt1 and Spelt52 was studied in Triticum species representing 2 evolutionary lineages of wheat and in Aegilops sect. Sitopsis, putative donors of their B/G genomes. Using fluorescence in situ hybridization we observed considerable polymorphisms in the hybridization patterns of Spelt1 and Spelt52 repeats between and within Triticum and Aegilops species. Between 2 and 28 subtelomeric sites of Spelt1 probe were detected in Ae. speltoidies, depending on accession. From 8 to 12 Spelt1 subtelomeric sites were observed in species of Timopheevi group (GAt genome), whereas the number of signals in emmer/aestivum accessions was significantly less (from 0 to 6). Hybridization patterns of Spelt52 in Ae. speltoides, Ae. longissima, and Ae. sharonensis were species specific. Subtelomeric sites of Spelt52 repeat were detected only in T. araraticum (T. timopheevii), and their number and chromosomal location varied between accessions. Superimposing copy number data onto our phylogenetic scheme constructed from RAPD data suggests 2 major independent amplifications of Spelt52 and 1 of Spelt1 repeats in Aegilops divergence. It is likely that the Spelt1 amplification took place in the ancient Ae. speltoides before the divergence of polyploid wheats. The Spelt52 repeat was probably amplified in the lineage of Ae. speltoides prior to divergence of the allopolyploid T. timopheevii but after the divergence of T. durum. In a separate amplification event, Spelt52 copy number expanded in the common ancestor of Ae. longissima and Ae. sharonensis.

Base Sequence↗