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PubMed1974

The importance of gene rearrangement in evolution: evidence from studies on rates of chromosomal, protein, and anatomical evolution.

We have compared the relative rates of protein evolution and chromosomal evolution in frogs and mammals. The average rate of change in chromosome number has been about 20 times faster in mammals than in frogs. Whereas it takes only 3.5 million years, on the average, for a pair of mammal species to develop a difference in chromosome number, the corresponding period for frogs is 70 million years. In contrast, the rate of protein evolution in mammals has been roughly equal to that in frogs. The rapid rate of gene rearrangement in mammals parallels both their rapid anatomical evolution and their rapid evolutionary loss of the potential for interspecific hybridization. Thus, gene rearrangements may be more important than point mutations as sources for evolutionary changes in anatomy and way of life.

Adaptation, Biological↗
PubMed1999

A potential model for early stages of chromosomal evolution via concentric Robertsonian fans: a large area of polymorphism in southern short-tailed shrews (Blarina carolinensis).

Western Tennessee contains unusually highly polymorphic populations of southern short-tailed shrews (Blarina carolinensis). We previously documented eight Robertsonian translocations (ROBs) accounting for a variation in diploid number from 46 in most of this species' range to 34-40 in western Tennessee. We have now expanded our study to include data from adjacent areas in Tennessee and Mississippi, 10 localities in all. The new data show a variation in diploid number ranging from 31 to 41, four new ROBs (for a total of 12), and the novel finding of monobrachial translocations in this group. All animals collected from this large area (extending over 12, 000 km(2)) had some level of ROBs, and none represented the 2n = 46 form seen in other parts of the range of this species. Because other species of shrews (genus Sorex) are not affected in the same area, the factors and/or selective forces causing this extensive polymorphism in B. carolinensis must be unique to this species and to this geographic area. Some ROBs were found throughout this large area of over 12,000 km(2). Other translocations (including those with monobrachial homology) were located in one or two localities in this large area, and still other translocations were intermediate in their distribution. There was a concentric pattern to the evolution and presumed spreading of the ROBs. This allowed us to expand the concept of a Robertsonian "fan," introduced by Matthey (1970), to that of concentric evolution of multiple fusion fans: ROBs likely arose independently, separated temporally and geographically, and radiated into surrounding populations to create this complex zone of polymorphism. This is an active process in its infancy, and it is not as mature as that seen in European studies of Mus and Sorex.

Animals↗
PubMed2003

Genetic studies on premating isolation in Drosophila simulans. II. A D. simulans line highly crossable to males of D. yakuba and D. teissieri.

Females of the S1 line of Drosophila simulans, an isofemale line from a natural population at Mishima, Japan, were found to show high crossability to males of D. yakuba and D. teissieri. With D. yakuba males, 24.0-58.5% of the S1 females were inseminated, while the rate was only 0.0-6.3% for the control lines. The high crossability was ascribed to the genes on the X and third chromosomes. With D. teissieri males, 38.0-51.5% of the S1 females were inseminated, while the rate was only 0.0-6.2% for the control lines. The crossability was ascribed to the genes on the third chromosome, and possibly the second chromosome genes acted additively. The crossabilities of hybrid females between the S1 and the control lines were intermediate between the parental lines both to D. yakuba males and to D. teissieri males.

Animals↗
PubMed2005

[Divergence of the polytene chromosome banding sequences as a reflection of evolutionary rearrangements of the genome linear structure].

Banding sequences of five chromosomal arms (A, C, D, E, and F), accounting for about 70% of the total genome size in 63 Chironomus species, were used as phylogenetic markers to analyze divergence patterns of the linear genome structure during the evolution. The number of chromosomal breakpoints between the pairs of banding sequences compared served as a measure of divergence. It was demonstrated that the greater the divergence between the species compared, the higher the number of chromosomal breakpoints and the smaller the size of the conserved chromosomal regions. A banding sequences comparison in sibling species demonstrated a lower number of chromosomal breakpoints; the breakpoint number was maximum in a comparison of the banding sequences in the subgenera Chironomus and Camptochironomus. The use of the number of chromosomal breakpoints as a divergence measure provided establishment of phylogenetic relationships between 63 Chironomus species and discrimination of sibling species groups and cytocomplexes on a phylogenetic tree.

Animals↗
PubMedDate not supplied

[Unilateral congenital glaucoma].

The paper reports on the case of a 6-year-old child with OD congenital glaucoma and increase of the ocular globe volume with ruptures of Descemet's membrane. VARE = 1/8 non correcting, VALE = 34 mmHg, RE--divergent strabismus. The left microphthalmus with the corneal diameter of 9 mm. Normal karyotype. Trabeculectomy was performed at the right eye. Good postsurgical evolution. This is a case of phenocopy because in the development and formation of the iridocorneal angle in the sixth month of pregnancy, a series of extrinsic teratogenous factors appeared: measles, influenza, toxemia of pregnancy that produced modifications of the trabecula.

Child↗
PubMed1986

Cytogenetics of Dictyocaulus arnfieldi (Cobbod, 1884) Railliet and Henry, 1907.

A cytogenetic study of Dictyocaulus arnfieldi was made for the first time. The diploid chromosome number was 2n = 11 for males and 2n = 12 for females; there was an XO/XX sex determinism mechanism. Diplotene stage showed bivalents with 3, 2 or 1 chiasmata. The possible differences in the evolution of D. arnfieldi and Dictyocaulus filaria are discussed.

Animals↗
PubMed1980

Chromosomal evolution of 19 species of sub-species of Cercopithecinae.

Chromosome analysis by handling techniques of 19 species and sub-species of Cercopithecinae shows an important accumulation of chromosome rearrangements (51). With a clear predominance of fissions (26) and of inversions (17). It is impossible to reconstruct a simple genealogy of these species because chromosomal evolution did not follow the principle of a strict dichotomy. The progressive increase of the number of chromosomes, by fission, corresponds to the inverse of the Robertsonian evolution and suggests the existence of numerous interstitial centromeres and telomeres.

Animals↗
PubMed1977

Comparative investigation of DNA from mouse and Ehrlich ascites tumor cells.

Mouse DNA and DNA of Ehrlich ascites tumor have been comparatively studied in the search for changes in DNA during tumor progression. No differences were found in kinetics of homologous (mouse X mouse) and heterologous (mouse X tumor) DNA reassociation; in thermal stability of homologous and heterologous duplexes of repeated, unique and satellite DNA; in percentage of hybridization with mouse liver heterogenous nuclear RNA; in thermal stability of the RNA.DNA hybrids. The negative results suggest that the considerable evolution of transplantable tumors (both in biological properties and in karyotype) has not been accompanied by alterations of the genome which could be detected by the now available methods of molecular hybridization for studying DNA divergence. In the light of the results obtained the functions ascribed to the mouse satellite DNA are discussed.

Animals↗
PubMed2004

Evolution of clonal cytogenetic abnormalities in aplastic anemia.

Prior to the introduction of effective therapies, the high mortality rates of severe aplastic anemia (AA) precluded recognition of late complications of this disease. Once the survival of AA improved, observation of clonal evolution raised questions as to whether the development of secondary myelodysplastic syndrome (MDS) is a part of the extended natural history of the disease or is related to the therapies applied. Clinical features of myelodysplasia and AA can overlap, and typical MDS may evolve as a complication of AA. Common pathophysiologic elements operate in these diseases and are subject to many studies and theories as to what mechanisms in AA may lead to the late evolution of MDS. Similarly, AA has been hypothesized to be a reflection of an over-reactive immune response triggered by the appearance of genetically altered and/or phenotypically abnormal dysplastic clones. Hypocellular variants of myelodysplasia and responsiveness of certain forms of MDS to immunosuppressive regimens serve as the most appealing examples of the intricate and close pathophysiologic relationship of this disease with AA. The diagnosis of clonal evolution in the course of AA can be obvious if secondary cytopenia involves hypercellularity and a high percentage of blasts. In addition, the occurrence of a new karyotypic defect objectively heralds the progression of disease to MDS. However, the diagnostic imprecision of dysplasia recognition in the context of marrow hypocellularity, inability to obtain informative cytogenetics, and a high proportion of MDS cases with normal karyoptype have hampered studies designed to determine the frequency and timing of MDS evolution in AA. In addition, the diagnostic criteria and definitions used are not unified. While some centers recognize that the abnormal karyotype does not preclude the diagnosis of AA; in others, the diagnosis of AA includes the presence of normal karyoptype. Many typical features of dysplastic evolution in AA have been clarified. For example, karyotypes most frequently encountered in MDS secondary to AA involve chromosomes 6, 7 and 8. The evolution rates seem to be in the range of 10-15% in 10 years, but there are no predictive clues as to which patients are at greatest risk for this complication. Study of the mechanisms of clonal evolution in AA may help understand the pathophysiology of other forms of MDS and leukemia and also the mechanisms of antileukemic surveillance. Clinically, identification of patients at increased risk for clonal complications may influence the choice of therapies applied.

Anemia, Aplastic↗
PubMedDate not supplied

Centromere dynamics and chromosome evolution in marsupials.

The eukaryotic centromere poses an interesting evolutionary paradox: it is a chromatin entity indispensable to precise chromosome segregation in all eukaryotes, yet the DNA at the heart of the centromere is remarkably variable. Its important role of spindle attachment to the kinetochore during meiosis and mitosis notwithstanding, recent studies implicate the centromere as an active player in chromosome evolution and the divergence of species. This is exemplified by centromeric involvement in translocations, fusions, inversions, and centric shifts. Often species are defined karyotypically simply by the position of the centromere on certain chromosomes. Little is known about how the centromere, either as a functioning unit of chromatin or as a specific block of repetitive DNA sequences, acts in the creation of these types of chromosome rearrangements in an evolutionary context. Macropodine marsupials (kangaroos and wallabies) offer unique insights into current theories expositing centromere emergence during karyotypic diversification and speciation.

Animals↗
PubMed2000

A comparative study of chromosome morphology among the nine annual species of Cicer L.

Thirty-six accessions, representing the full complement of all the nine annual Cicer L. species, viz C. arietinum, C. reticulatum, C. echinospermum, C. pinnatifidum, C. judaicum, C. bijugum, C. chorassanicum, C. yamashitae and C. cuneatum, were subjected to karyotype analysis for the first time in a single comprehensive study. The detailed karyotype of C. chorassanicum was also investigated for the first time. A 12 h cold water pretreatment and 13 min 60 degrees C 1 N HCl hydrolysis confirmed a somatic chromosome number of 2n = 16 in all the species. Within species interchromosomal size variation was observed to be quite large in C. arietinum, C. reticulatum and C. echinospermum, but not in the remaining six species. Individual chromosome size ranged from 3.77 microns in C. echinospermum to 1.32 microns in C. arietinum while the haploid genome length ranged from 20.65 microns in C. echinospermum to 14.92 microns in C. cuneatum. Ample rearrangement of chromatin among chromosomes within a species was implied to have played a role in Cicer genome evolution. The nine species were classified in two groups based on karyotypic similarity, with the first group comprising the inter-crossable species C. arietinum, C. reticulatum and C. echinospermum, while the remaining species forming the second group. The first group species are also genetically close to each other as deduced by other morphological, biochemical and DNA based studies. Circumstantial evidence has lead to the speculation that perhaps karyotypic similarity and interspecific crossability are positively related to each other.

Centromere↗
PubMed1976

New karyological data of Rhinoderma: the chromosomes of Rhinoderma rufum.

The chromosomes of the Chilean frog Rhinoderma rufum are described for the first time. This chromosome set is compared with the karyotype of R. darwinii. The importance of the karyological data applied to the phylogeny and systematics of this genus are discussed. A tentative hypothesis of karyological evolution of Rhinoderma is given.

Animals↗
PubMed2006

A cytological study on Kelloggia (Rubiaceae), an intercontinental disjunct genus between eastern Asia and western North America.

A cytological study was carried out for the first time on four populations of the only two species of Kelloggia (Rubiaceae), which occur disjunctly in eastern Asia (K. chinensis Franch.) and western North America (K. galioides Torr.). The consistent mitotic prophase chromosome condensation pattern and interphase nuclei type were determined for both species. The chromosome base number of the genus is suggested to be x = 11. The karyotype of 2n = 22 = 2x = 16m + 6sm was examined for both species. The karyotypical asymmetry of 1A and 2A was found in K. chinensis and K. galioides, respectively. According to the predominant evolutionary direction of karyotype asymmetry in angiosperms, K. galioides (2A) seems slightly more evolved than K. chinensis (1A). Our finding is consistent with the hypothesis of the Old World origin of Kelloggia based on molecular study.

Biological Evolution↗