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Results for “karyotype evolution”

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At least 1,009 records · Page 56Linked to original sources
PubMed1998

Cytogenetic comparison of primary tumors and lymph node metastases in breast cancer patients.

Chromosome banding analysis of primary tumors and axillary lymph node metastases from 10 breast cancer patients revealed abnormal karyotypes in all samples with cytogenetic similarities between the primary tumor and the metastasis in all informative pairs. Although karyotypically unrelated clones were also found in the lymph node samples, they were less numerous than in the primary tumors, indicating that there was more genetic heterogeneity among the neoplastic cells in the primary than in the secondary tumors. On the other hand, some of the clones had become more complex in the metastases as a result of clonal evolution, and by and large these metastatic breast cancer cases had more karyotypic anomalies than do unselected primary breast carcinomas. Among the aberrations occurring more frequently, and that consequently may predispose to disease spread, were losses of chromosomes 17 and 22 and homogeneously staining regions, a cytogenetic sign of gene amplification.

Adult↗
PubMed1992

Evolution of pericentromeric heterochromatin of human X chromosome.

An unusual large heterochromatic segment around the pericentromeric region of the X-chromosome is reported. In normal circumstances, the pericentromeric region of the X-chromosome is negative by the restriction endonuclease AluI/Giemsa technique. However, this unusual X-chromosome was found to have AluI resistant (positive) chromatin. The evolution of extra heterochromatin is a postzygotic event as substantiated by the presence of a normal cell line.

Biological Evolution↗
PubMed1998

Cytogenic studies of Hynobiidae (Urodela). XIV. Analysis of the chromosome of a Chinese salamander, Batrachuperus pinchonii (David).

The chromosome number of a Chinese salamander, Batrachuperus pinchonii, was re-examined Adults and embryonic specimens had a diploid number of 66, with 33 bivalents during meiosis, in contrast to previous reported results. Furthermore, when C-banding analysis was performed with embryos, chromosomes with banding patterns homoeologous to those of Salamandrella keyserlingii and Hynobius species were found. It appears, therefore, that Batrachuperus, Salamandrella and Hynobius might be derived from a common ancestral species in eastern Asia.

Animals↗
PubMed2003

Molecular cytogenetic analysis and centromeric satellite organization of a novel 8;11 translocation in sheep: a possible intermediate in biarmed chromosome evolution.

During analysis of genome organization in sheep (Ovis aries, 2n = 54, XY/XX), we found a novel chromosomal translocation in an animal expected to be normal, adding to the six 'centric fusions' previously reported. The translocation was identified as t(8;11) by G-banding and was shown to be centric, involving whole chromosome arms by chromosome painting with probes for Chromosomes (Chrs) 8 and 11. Satellite I and a newly isolated satellite II clone was used to characterize the centromeric regions of both the novel and the three pairs of evolutionarily derived biarmed chromosomes. The novel t(8;11) showed satellite I proximal on both arms with satellite II covering the centromere, while the evolutionarily derived fusion leading to Chrs 2 and 3 showed the opposite configuration, not obviously derived by a simple fusion. Chr 1 has lost the satellite I hybridization patterns. The novel t(8;11) provides strong evidence for an intermediate step in evolution of the biarmed chromosomes in sheep.

Animals↗
PubMed1998

Sex determination in plants.

The majority of flowering plants produce flowers that are "perfect." These flowers are both staminate (with stamens) and pistillate (with one or more carpels). In a small number of species, there is spatial separation of the sexual organs either as monoecy, where the male and female organs are carried on separate flowers on the same plant, or dioecy, where male and female flowers are carried on separate male (staminate) or female (pistillate) individuals. Sex determination systems in plants, leading to unisexuality as monoecy or dioecy, have evolved independently many times. In dioecious plant species, the point of divergence from the hermaphrodite pattern shows wide variation between species, implying that the genetic bases are very different. This review considers monoecious and dioecious flowering plants and focuses on the underlying genetic and molecular mechanisms. We propose that dioecy arises either from monoecy as an environmentally unstable system controlled by plant growth substances or from hermaphroditism where the underlying mechanisms are highly stable and control does not involve plant growth substances.

Animals↗
PubMed2003

Reciprocal chromosome painting shows that squirrels, unlike murid rodents, have a highly conserved genome organization.

We present the first report of reciprocal chromosome painting between humans and a rodent. Gene mapping and sequencing data lead to the generalization that rodent genomes are highly rearranged. In contrast, our results show a surprising conservation of genome structure between humans and squirrels. The synteny of 12 human chromosomes was entirely conserved (5, 6, 9, 11, 13-15, 17, 18, 20, 21, and X). Of the 12 syntenic associations of human chromosomes present in the squirrel, six are well-known ancestral eutherian associations (3/21, 4/8, 7/16, 12/22, 14/15, 16/19). Apparently, few derived translocations characterize the evolutionary origin of the rodents. One association (10p/1qter) may be a cladistic marker for the cohort Glires, linking rodents and lagomorphs.

Animals↗
PubMed1997

Geographical distribution of B chromosomes in the grasshopper Eyprepocnemis plorans, along a river basin, is mainly shaped by non-selective historical events.

The analysis of 19 populations of the grasshopper Eyprepocnemis plorans, collected along four rivers belonging to the Segura basin (Mundo, Benamor, Taibilla and Segura itself), has shown that the presence of B chromosomes ends abruptly in each river, coinciding with the existence of a narrow pass in which this grasshopper cannot live because of the absence of the appropriate habitats. The existence of a broad inland region lacking grasshoppers with B chromosomes suggests that B chromosomes arose after the first colonization of the Iberian Peninsula by E. plorans specimens from North African populations. The B chromosome seems to have spread upstream along each of these four rivers until reaching geographical barriers that have impeded its advance and thus have preserved the non-B chromosome region. The available evidence indicates that the observed geographical distribution of the B chromosome polymorphism in this zone was shaped mainly by historical non-selective events.

Altitude↗
PubMed2003

Karyological and genetic variation in Middle Eastern lacertid lizards, Lacerta laevis and the Lacerta kulzeri complex: a case of chromosomal allopatric speciation.

Karyological (standard and C, Ag-NOR and Alu-I banding methods) and mtDNA analyses (cytochrome b and 12S rRNA) were conducted on specimens from eight allopatric populations of the Lacerta kulzeri complex. Parallel analyses were performed for comparison on Lacerta laevis specimens. Karyological and molecular studies support the morphological and ethological evidence indicating the specific separation between Lacerta laevis and Lacerta kulzeri. In the Lacerta kulzeri complex, chromosomal analysis substantiated an interpopulation differentiation roughly along a north-south trend, mainly regarding the sex chromosome morphology and heterochromatin. The cytochrome b and 12S rRNA gene analyses showed minor genetic differences that were considerably smaller than those commonly found in genetically isolated populations. The L. kulzeri populations from Barouk, Druze and Hermon show a mean genetic distance that, in other saurians, characterises subspecies. The conditions found in L. laevis and L. kulzeri are reminiscent of King's model of chromosomal primary allopatry and support the hypothesis that in these lacertid lizards chromosome variations can become fixed before the accumulation of the genetic mutations.

Animals↗
PubMed2004

Comparative analysis (Hippotragini versus Caprini, Bovidae) of X-chromosome's constitutive heterochromatin by in situ restriction endonuclease digestion: X-chromosome constitutive heterochromatin evolution.

The Bovidae X-chromosome shows a considerable variation, in contrast to the preservative autosomal conservatism. The X-chromosome variation is mostly a consequence of the constitutive heterochromatin (CH) variation; in what respect to its amount and position. This is especially common among the non-Bovinae subfamilies and tribes. In order to characterize the X-chromosome CH in non-Bovinae species--Hippotragini and Caprini tribes--we have used restriction endonuclease digestion on fixed chromosomes and sequential C-banding. With these techniques we were able to distinguish between the two X-chromosome types (Hippotragini and Caprini) CH, in what respect to its position and molecular nature. Moreover, we define at least, six subclasses of CH in both X-chromosome types analyzed. Evolutionary considerations were draw based on the results obtained. The technology used here for the analysis of the Bovidae X-chromosome CH showed to be more evolutionary informative than the classical approaches.

Animals↗