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Results for “karyotype evolution”

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PubMed2002

Different genomic evolutionary rates in the various reptile lineages.

Although Reptiles occupy a strategic position among terrestrial vertebrates, studies of the composition and evolution of their genome are scarce. The cytogenetic analysis of nearly 1400 species evidenced different karyotypical evolutionary rates and different G-banding structures in turtles and crocodiles on the one hand and squamates on the other. A similar dichotomy was also identified through the study of the quantitative and compositional characteristics of the genome. The different evolutionary rates of chromosome morphology and genome size and composition and the diversification of coding and non-coding sequences bear an interesting relationship to the number of extant species and the extinction rates of the reptilian orders and suborders studied, suggesting a large role for such different evolutionary rates in the phylogenesis of this class. The different molecular and structural organisation of chromosomes could be an important, though by no means the sole, factor affecting the genome's evolutionary rate.

Alligators and Crocodiles↗
PubMed1998

Emergence of secondary acute leukemia in a patient treated for osteosarcoma: implications of germline TP53 mutations.

BACKGROUND: Secondary leukemia and myelodysplastic syndromes have been reported in patients following treatment for a wide range of neoplastic disorders. However second malignancies after chemotherapy and/or irradiation for osteosarcoma are unusual. PROCEDURE: We report the case of a 15-year-old girl who developed a myelodysplastic syndrome with evolution to acute nonlymphocytic leukemia after treatment for osteosarcoma. Therapy-related acute leukemia karyotype findings such as abnormalities of chromosomes 5, 7, and 17 were found in the cytogenetic analysis. Moreover, using denaturing gradient gel electrophoresis and DNA sequencing, we detected the presence of a double germline mutation in exon 7 of the TP53 gene. CONCLUSION: This observation supports the possibility of a causal relationship between germline TP53 mutations and the development of secondary leukemia and myelodysplasia.

Adolescent↗
PubMed2000

Sex chromosome evolution in fish: the formation of the neo-Y chromosome in Eigenmannia (Gymnotiformes).

Chromosomes of a species of Eigenmannia presenting a X1X1X2X2:X1X2Y sex chromosome system, resulting from a Y-autosome Robertsonian translocation, were analyzed using the C-banding technique, chromomycin A3 (CMA3) and mithramycin (MM) staining and in situ digestion by the restriction endonuclease AluI. A comparison of the metacentric Y chromosome of males with the corresponding acrocentrics in females indicated that a C-band-positive, CMA3/MM-fluorescent and AluI digestion-resistant region had been lost during the process of translocation, resulting in a diminution of heterochromatin in the males. It is hypothesized that the presence of a smaller amount of G + C-rich heterochromatin in the sex chromosomes of the heteromorphic sex when compared with the homomorphic sex may be associated with the sex determination mechanism in this species and may be a more widely occurring phenomenon in fish with differentiated sex chromosomes than was initially thought.

Animals↗
PubMed2002

Cytological study of Tibetia (Fabaceae) in the Hengduan Mountains region, China.

The Hengduan Mountains comprise one of the world's most important hot spots of biodiversity. Tibetia (Ali) H.P. Tsui (Fabaceae), which has four or five species in two sections, is one of the genera endemic to the region. This paper describes for the first time the karyotype of three of those species. The chromosome counts of all three are 2 n = 16. The karyotypes of the species examined contain chromosomes of variable karyotypic symmetry with centromeres at median and submedian positions that correlate with the morphological characteristics of the species. Karyotypic variation at the diploid level appears to be the predominant feature of chromosome evolution in the genus and may provide a clue to the study of evolutionary patterns of plants in this region.

Journal Article↗
PubMed2005

Multiple origins of tetraploid taxa in the Eurasian Bufo viridis subgroup.

We used Q-banding and analyzed nucleolar organizing regions (NORs) to study the cytogenetic evolution of tetraploids within the Palearctic Bufo viridis subgroup, the only known amphibian complex comprising di-, tri- and tetraploid bisexually reproducing taxa. We examined three diploid (2n) nominal taxa (Bufo viridis viridis, B. v. turanensis, B. v. kermanensis) from five Eurasian localities and six tetraploid (4n) nominal taxa (B. oblongus, B. o. danatensis, B. pewzowi pewzowi, B. p. taxkorensis, B. p. unicolor, B. p. strauchi) from eight Central Asian localities. Homeologous chromosomes of 2n and 4n toads exhibit a similar morphology. Silver-staining and in situ hybridization revealed terminal NORs in the long arms of chromosomes 6 in all 2n but in only two out of four chromosomes 6 in all 4n taxa. Q-banding and a rapidly evolving mitochondrial marker suggest at least two origination events for Asian 4n toads: "Western Central Asian tetraploids" (B. oblongus Nikolsky, 1896) exhibit distinct differences within some chromosome quartets, which are divisible into pairs of chromosomes and may be allopolyploid. In contrast, "Central Asian tetraploids" (B. pewzowi Bedriaga, 1898) showed homogenous Q-banding patterns within each quartet, suggesting autopolyploidy. In Northeastern Iran, we discovered a zone of either common ancestry or hybridization of 2n and Western Central Asian 4n toads. This raises intriguing questions about how diploid and tetraploid taxa may evolve by exchanging genetic material.

Animals↗
PubMed2006

Chromosome rearrangements in Pectinidae (Bivalvia: Pteriomorphia) implied based on chromosomal localization of histone H3 gene in four scallops.

Chromosomal structural rearrangement in four scallops, Chlamys farreri (n=19), Patinopecten yessoensis (n=19), Chlamys nobilis (n=16) and Argopecten irradians (n=16), was studied by fluorescence in situ hybridization using histone H3 gene probes. The results show that histone H3 gene sites differ strikingly with regard to number, location, and intensity among, or even within these species. For example, two histone H3 gene loci were detected on the metaphase chromosomes of P. yessoensis, while one locus was found in the others. In P. yessoensis, differing intensities of hybridization signals were detected between homologues 5 and 11, and within homologue 11. These data suggest that the histone H3 gene is a qualified chromosome marker for the preliminary understanding of the historical chromosomal reconstructing of the Pectinidae family. The variable distribution patterns of the histone H3 gene suggest that gene duplication/diminution as well as chromosome rearrangements by inversion and translocation may have played important roles in the genomic evolution of Pectinidae. We also compiled our present results with former published data regarding the chromosome mapping of rDNAs in species of the Pectinidae family. Such comparative chromosomal mapping should improve our understanding of historical chromosomal reconstructions of modern-day scallops.

Animals↗
PubMed1991

Gene mapping in marsupials: detection of an ancient autosomal gene cluster.

The genes HRAS, HBB, and CAT, which are located together on the short arm of human chromosome 11, appear to be part of a conserved synteny group found in many eutherian mammals. These genes were mapped to the chromosomes of two marsupial (metatherian) species by in situ hybridization. All three genes were located together on chromosome 3 in Macropus eugenii. Only HRAS and CAT were used to probe Dasykaluta rosamondae metaphases and these genes both mapped to chromosome 4. This suggests that the HRAS-HBB-CAT gene cluster has been conserved at least since the metatherians and eutherians diverged some 130 million years ago. These findings support the concept of a mammalian genome that has remained highly conserved throughout evolution.

Animals↗
PubMed1993

Radiation of chromosome shuffles.

Rock wallabies, Petrogale, exhibit chromosome diversity that is exceptional in marsupials, with 20 distinct chromosome races being recognized. Many of the karyotypic changes identified within Petrogale appear to be recent, although the rate of chromosome evolution varies between taxa. While the patchy distribution of Petrogale and their social structure would facilitate the fixation of novel rearrangements, these factors alone do not explain the pattern of chromosome evolution shown in this group. The chromosome changes that have come to characterize each taxon may offer selective advantages in the particular areas occupied, or it may be that these rearrangements play an important role in reproductive isolation. In Petrogale, the taxa with the largest number of chromosome rearrangements are those that are sympatric, or have multiple zones of parapatry, with other members of the genus. Male hybrids from a variety of chromosomal admixtures were found to be sterile, but with those heterozygous for the least complex rearrangements being least affected. As expected, equivalent female hybrids were less severely affected. Chromosomal and genic changes both appear important in these processes.

Animals↗
PubMedDate not supplied

Mosaic trisomy 15 and hemihypertrophy.

We report a case of mosaic trisomy 15 with mental retardation, facial dysmorphism, and hemihypertrophy, but no manifestations of Prader-Willi or Angelman syndromes. Mosaic trisomy 15 (11%) was discovered at the amniocentesis. Uniparental disomy for chromosome 15 was excluded by molecular analysis. Post-natal blood karyotype and examination were normal. Mosaic was confirmed on skin fibroblasts, placenta and cord. Evolution was marked by progressive right hemi-hypertrophy, and developmental delay. Our case is the first patient reported with hemihypertrophy associated with mosaic trisomy 15. The relevant literature is reviewed.

Adult↗
PubMed1984

Genomic alterations involving the c-myc proto-oncogene locus during the evolution of a case of chronic granulocytic leukaemia.

In a patient with Ph-positive chronic granulocytic leukaemia who had 3 separate episodes of promyelocytic transformation associated with new cytogenetic and genetic changes DNA from the peripheral-blood leucocytes obtained during the second episode of transformation showed an 8-fold to 16-fold amplification of cellular myc proto-oncogene (c-myc) sequences, and rearrangement of these sequences. There was no amplification or rearrangement of c-myc sequences in DNA from leucocytes collected during the chronic phase, nor were these sequences amplified in DNA from leucocytes collected during the third episode of transformation. These observations show that new clones of cells that proliferate during the evolution of a myeloid leukaemia can carry genetic changes in addition to any recognisable karyotypic changes. Such genetic changes might underlie the progression of the disease.

Adult↗
PubMed2000

Polysomy 13 with concomitant deletion of 13q13-14 involving the retinoblastoma gene and the D13S25 locus in a case of acute myeloid leukemia.

We herein describe a case of acute myeloblastic leukemia (AML), FAB subtype M4, with an unfavorable clinical course and a complex karyotype, including 4-9 copies of chromosome 13. Polysomy 13 was a result of clonal evolution. Fluorescence in situ hybridization (FISH) revealed a cytogenetically unrecognizable deletion within 13q13-14 that included the retinoblastoma gene (RB) and the D13S25 locus in all but one copy of chromosome 13. The only chromosome 13 that did not show a deletion affecting the q13-14 region was translocated to chromosome 7, resulting in a dic(7;13)(q21;p11). In this case, the coexistence of polysomy and a partial deletion within the same chromosome point toward a possible formation of a fusion product with oncogenic potential and its consecutive amplification as a critical alteration in this case.

Aged↗
PubMed2000

Inactive ribosomal cistrons are spread throughout the B chromosomes of Rattus rattus (Rodentia, Muridae). Implications for their origin and evolution.

In-situ hybridization with a rDNA probe has demonstrated the presence of non-transcribed ribosomal genes in the B chromosomes of the black rat Rattus rattus. To test whether methylation of ribosomal DNA present in the B chromosomes could account for their inactivation, we performed in-situ digestions and Southern analyses of DNA digested with the isoschizomers MspI and HpaII. Our results suggest that the accessory chromosomes of this species have originated from one of the smaller NOR-carrying chromosome pairs. In the course of evolution, repetitive sequences invaded this supernumerary element and its ribosomal DNA content was dispersed throughout the chromosome and inactivated by heterochromatinization and methylation.

Animals↗
PubMed2002

A comparative cytogenetic study of five piranha species (Serrasalmus, Serrasalminae) from the Amazon basin.

Cytogenetic studies were conducted on five piranha species belonging to the genus Serrasalmus, subfamily Serrasalminae (Serrasalmus altispinis, S. compressus, S. elongatus, S. manuelli, and S. spilopleura). All the species were collected in the Amazon basin: confluence of Negro and Solimões Rivers (CatalãoLake), Solimões River (Marchantaria Island - Camaleão Lake), Uatumã River (Hydroelectric Power Station of Balbina), and Pitinga River (Hydroelectric Power Station of Pitinga). All the five species possess 2n = 60 chromosomes with 5-12 subtelo-and acrocentric chromosomes bearing nucleolar organizer regions. A proximal C-band positive heterochromatin block was evident on the long arms of a medium-sized metacentric chromosome pair in all the analized species, thus making it a cytogenetic marker for the genus. It is hypothesized that 2n = 60 chromosomes represents a derived feature in terms of the chromosomal evolution of piranhas because the basal lineages possess 2n = 62. Both Robertsonian centric fusion and non-Robertsonian rearragements such as pericentric inversions seem implicated in the chromosomal evolution of this group.

Animals↗
PubMed2001

Evolutionary dynamics and chromosomal distribution of repetitive sequences on chromosomes of Aegilops speltoides revealed by genomic in situ hybridization.

Simultaneous genomic in situ hybridization (GISH) with probe preannealing was used to detect the relationship between chromosomal position and sequence conservation on Aegilops speltoides var. aucheri chromosomes. DNA of Secale sylvestre, Hordeum spontaneum, Festuca pratensis, Semiarundinaria fastuosa, Arundo donax and Zea mays that represent several main groups of Poaceae were used as probes. Different GISH-banding patterns that characterize diverse evolutionary trajectories in the repetitive DNA fraction and correlate with evolutionary distance between tested species were observed. Fast-evolving sequences were detected in subterminal telomeric and subtelomeric heterochromatic regions, whereas sequences in pericentromeric regions showed high levels of conservation. GISH experiments revealed extensive conservation in NOR regions on chromosomes 1 and 6 which, in fact, appears to be a complicated mix of rDNA clusters and heterochromatin blocks of different nucleotide composition.

Chromosome Banding↗
PubMed1997

Recombination and gene flux caused by gene conversion and crossing over in inversion heterokaryotypes.

A theoretical analysis of the effects of inversions on recombination and gene flux between arrangements caused by gene conversion and crossing over was carried out. Two different mathematical models of recombination were used: the Poisson model (without interference) and the Counting model (with interference). The main results are as follows. (1) Recombination and gene flux are highly site-dependent both inside and outside the inverted regions. (2) Crossing over overwhelms gene conversion as a cause of gene flux in large inversions, while conversion becomes relatively significant in short inversions and in regions around the breakpoints. (3) Under the Counting model the recombination rate between two markers depends strongly on the position of the markers along the inverted segment. Two equally spaced markers in the central part of the inverted segment have less recombination than if they are in a more extreme position. (4) Inversions affect recombination rates in the univerted regions of the chromosome. Recombination increases in the distal segment and decreases in the proximal segment. These results provide an explanation for a number of observations reported in the literature. Because inversions are ubiquitous in the evolutionary history of many Drosophila species, the effects of inversions on recombination are expected to influence DNA variation patterns.

Animals↗