Cytogenetic Basis Research Articles

Cytogenetic basis of breeding system in some verbenaceous species.

To determine the cytogenetical basis of breeding systems, detailed vegetative and floral features along with the chiasmata/nucleus/bivalent have been investigated in two successful colonising species Lippia nodiflora and L. geminata. These attributes have been compared with those in two non-colonising ornamentals, Verbena hybrida and V. bonariensis. The comparative analysis of data indicates that colonising species possess besides dynamic breeding mechanisms like vegetative, selling and outcrossing, a significantly higher chiasmata/bivalent resulting in high frequency of gene reshuffling. The ornamentals on the other hand have only sexual mode of breeding, mostly outcrossing, and lower chiasmata per bivalent. This differential behaviour between the two groups of species enables the colonisers to thrive in adverse ecological niches under rigorous natural selection whereas the ornamentals thrive only under human care and nurture.

Cytogenetic studies of leafy spurge, Euphorbia esula, and its allies (Euphorbiaceae)

Cytological and cytogenetic studies were carried out on populations of leafy spurge (Euphorbia esula L. s.l.) and its allies primarily from North America but also from Europe. Chromosome numbers were determined for 126 samples of E. esula, 11 of E. cyparissias L., 1 of the hybrid (E. ×pseudoesula Schur) between these two species, and 1 of E. agraria Bieb. All plants of E. esula were hexaploid. Of the total, 125 leafy spurge accessions had a chromosome number of n = 30; 1 of n = 25++. Very few meiotic abnormalities were observed. Euphorbia cyparissias was primarily tetraploid (n = 20), although occasional diploids (n = 10) were encountered. Tetraploids were fertile; diploids were sterile. The hybrid between the two foregoing species had a chromosome number of n = 25, indicating that the E. cyparissias parent was a tetraploid; meiosis in the hybrid was abnormal. Euphorbia agraria was found to have a gametic number of n = 20, which is the first chromosome number determination for this species; meiosis was normal. Artificial crosses were made successfully between 31 accessions of leafy spurge. Seed germination of the F1 progeny slightly exceeded that reported for natural populations, and meiosis was normal. Pollen stability studies were carried out on herbarium material. Stainability was 100% for most of the samples studied. Extensive pollen size polymorphism was found. It is suggested that this phenomenon supports the hypothesis that E. esula is of allopolyploid origin. No cytological or cytogenetic basis was found for considering the leafy spurge accessions examined in this study as other than as a single, albeit somewhat polymorphic, species.

Cytogenetic basis of human cancer

The significance of germ-line and somatic genetic changes to the etiology of cancer has been a subject of continuing interest for cancer cell biologists. Recognition of certain basic principles of cancer cell genetics such as the clonal nature of tumors and their dynamic genetic systems were the early results of these studies, which mainly related to chromosomes in tumor cells. Recent advances in techniques of chromosome analysis and the integration of tumor cytogenetics with immunology and molecular genetics have permitted extraordinary insights into the nature of the perturbations that gene structure and function undergo in cancer cells. These developments have been reviewed here in so far as they address the central issue of cancer genetics, namely, the role of somatic and gerrn-line chromosome change in the origin and evolution of neopolastic cells.

A Cytogenetic Basis for Transferring Russian Wildrye from Elymus to Psathyrostachys1

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski, is a native grass of the Asian interior, but it has become in important range grass in western North America where it is known as Elymus junceus Fsisch. The purposes of this investigation were 1) to determine the genome relationships between Russian wildrye and Psathyrostachys fragilis (Boiss.) Nevski, and 2) to determine the appropriate taxonomic treatment of Russian wildrye. After several unsuccessful attempts, Russian wildrye was hybridized with P. fragilis in 1979. The parents and hybrids were diploid, 2n=14. More than half of the Metaphase‐I cells in the F1 hybrids contained seven bivalents, demonstrating that the genomes of Russian wildrye and P. fragilis are closely homologous. The hybrids produced up to 5% stainable pollen, thus permitting introgression between the parent species. The cytogenetic data leave no doubt that Russian wildrye and P. fragilis are closely related and should be placed in the same genus, Psathyrostachys. The appropriate name for Russian wildrye is therefore P. juncea. European and Asian taxonomists are using this name, which should also be accepted in North America.

Biological significance of liver cell polyploidy: an hypothesis

The liver cell polyploidy phenomenon, a characteristic of many species of mammals, is reviewed. The liver parenchyma of adult animals represents a mixed population of mononuclear and binuclear cells with different number of chromosome sets and, therefore DNA content per nucleus. The polyploid hepatocytes are formed during postnatal liver growth as a result of a change from normal mitoses to polyploidizing ones. Hence, the polyploidization of hepatocytes is regarded as an equivalent of cell multiplication. An hypothesis of the biological significance of liver cell polyploidy is based on the fact of a high level of spontaneous chromosome aberrations in mitotic hepatocytes. Ploidy increase is known to give resistance against different kinds of genome alteration. Polyploidization of the liver cells ensures protection against deleterious consequences of the aberrant genome formation resulting from aberrant mitoses. Some implications of the hypothesis are discussed: the reasons for species-specific differences of liver cell polyploidy; the mechanisms of hepatocyte radioresistance; the relation of polyploidy to liver cell aging. The prerequisite factors for unbalanced cell genome formation are adduced: DNA and chromosome damage as the first step in the process, stimulation of mitosis as the second one. The aberrant polyploid genome of hepatocytes is assumed to be the cytogenetic basis for some chronic liver diseases in man.

The cytogenetic basis of dominant-lethal mutations in mice: studies with TEM, EMS, and 6-mercaptopurine

The cytogenetic basis of dominant-lethal mutations in mice: studies with TEM, EMS, and 6-mercaptopurine

Studies on chemically induced dominant lethality. I. The cytogenetic basis of MMS-induced dominant lethality in post-meiotic male germ cells

Young adult male mice were injected intravenously with doses of methyl methanesulfonate(MMS) ranging from 25 to 100 mg/kg body weight. These males were serially mated to superovulated females from day 1 post injection to day 23 post injection. The morning after mating (about 4–6 h post-copulation) the females were sacrificed and ova flushed from the ampulla. The ova were cultured, in the presence of colchicine, for 26 h and metaphase preparations made of the first cleavage division. Chromosome analysis was done and the types, and extent, of chromosome aberrations correlated to previously published dominant lethal data at the same MMS doses and time intervals. The types of aberrations seen were predominantly double fragments (presumably isochromatid deletions), chromatid interchanges, and some chromatid deletions, as well as shattering effect on the male complement at the highest dose and the time of peak sensitivity to dominant lethal induction. When the frequency of cells containing a cytologically visible aberration is compared to the total dominant lethal data an excellent correlation is obtained. Furthermore, the frequency of highly damaged cells, agrees very well with estimated frequencies of preimplantation loss. These data strongly suggest that chromosome aberrations seen at the first cleavage stage are the basis of MMS-induced dominant lethality.

Cytogenetic Basis of Acute Myeloid Leukemia

The chromosomes of 12 adult patients with acute leukemia were analyzed by conventional means and by Giemsa and centromeric banding techniques. Acute myeloblastic leukemia was diagnosed in 7, acute myelomonocytic leukemia in 2, and acute undifferentiated leukemia in 3. Bone marrow was aspirated from patients when in relapse or remission, and both euploid and aneuploid cells were examined. All patients showed trisomy no. 9 and many showed additional numerical or structural changes in some or all their cells. These changes included monosomy no. 21 and/or monosomy no. 8. The proportion of trisomy no. 9 cells was 30-50% in patients in full remission and up to 100% in patients in relapse; thus trisomy no. 9 might be an important marker of leukemic cells. A mechanism was proposed to explain the induction and selection of the trisomy no. 9 karotype.

Reduction malformations and chromosome anomalies.

Three infants were born with serious limb defects (reduction malformations) and chromosomal anomalies. Other cases of skeletal malformations of the extremities that are associated with cytogenetic changes have been previously reported. The chromosomal anomaly usually is betrayed by associated malformations rather than by the type of limb defect. The recognition of the cytogenetic basis of limb malformation is of importance because it may influence the individual prognosis and genetic counseling.

An Interactive Chromosone Scanning System

To the relatively few groups actively engaged in automated chromosome studies, the title of this paper is rather self explanatory because it proposes to address a problem which has become apparent to all of us who have sought to automate cell analysis. The need for human interaction implies that our automated procedures are not error free and require some degree of human verification and correction within the procedure. Indeed this is so. The fact that a problem exists may be attributed to an over-optimistic concept of the capability of machines to duplicate apparently simple human activity. It follows that certainly one purpose of this paper would be to discuss the need for human interaction in automated chromosome analysis and to suggest an approach to the question of where and how interaction should be implemented. However, so that others who may be unfamiliar with automated chromosome analysis can achieve a better understanding, the format of this paper includes a brief overview of human cytogenetics along with an attempt to treat the significance of chromosome abnormalities in terms of the need for population studies. Unfortunately, the justification for automated procedures in cytogenetics has been based upon the need to reduce the labor and tedium involved in large studies without the need for the large studies themselves being clearly established on a cytogenetic basis.

Cytogenetic studies of Poecilia (Pisces). I. Chromosome numbers of naturally occurring poeciliid species and their hybrids from Eastern Mexico.

Cytological studies of fish from the subgenus Poecilia (Pisces) including members of an all-female species, P. formosa, have clearly shown diploid, somatic chromosome complements and Robertsonian arm numbers of 46. A triploid somatic chromosome complement of 3N = 69 was demonstrated for members of a naturally occurring variant clone of P. formosa, a form whose general body morphology closely resembles that of its sympatric species P. mexicana. Chromosomes of the different poeciliid species studied are remarkably similar in size, shape and structure, being mostly short acrocentrics, 2 μ long or less.The presence of a chromosome bearing a sub-terminal centromere within the complement of the Amazon molly provides the only direct evidence to date of centric shifts within the chromosome complement of the subgenus Poecilia. This finding also provides the first plausible cytogenetic basis for concluding that P. formosa is of relatively recent origin. Comparisons of relative chromosome lengths from both mitotic and meiotic configurations of related species indicate that the heteromorphic chromosome pair of P. formosa probably was derived by hybridization between P. latipinna and P. mexicana. Finally, as suggested by the numbers and forms of chromosomes in atypical, triploid specimens of P. formosa, their complements apparently contain both a maternal diploid set of chromosomes from the all-female species, and a paternal haploid set of chromosomes from P. mexicana.

KARYOTYPIC CLONAL EVOLUTION IN A CYSTIC ADENOMA OF THE OVARY

Short-term culture of cells from a cystic adenoma of the ovary removed from a 66-year-old woman, revealed normal cells, cells with a supernumerary C chromosome, and cells with two apparently similar C chromosomes. This was interpreted as evidence of clonal evolution, firstly by acquisition of a supernumerary chromosome followed by its occasional duplication leading to a second clone with 48 chromosomes. The chromosomal finding and the histological appearance of the tumour agree in indicating that this case illustrates the cytogenetic basis for the beginning of an evolution towards malignancy.