Structural Chromosome Mutations Research Articles

Multiple Chromosomal Polymorphism in Birch Mice of the Subtilis Group (Rodentia, Dipodoidea, <i>Sicista</i>) from Saratov Right Bank

Cytogenetic analysis (routine, G-, C-, AgNOR-chromosome banding) allowed to obtain new data on chromosomal polymorphism in the population (n = 13) of Sicista sp. 1, representative of the Sicista subtilis group from the Saratov Region, right bank of Volga River. It was shown that in the studied polymorphic population of a species from the northern part of the species' range (Voskresensky district of the Saratov region) the diploid number of chromosomes varies from 2n = 22 to 2n = 24, and the number of autosome arms from NFa = 39 to NFa = 44, and the sample includes the following 6 karyotype variants: with 2n = 24, NFa = 44; 2n = 24, NFa = 43; 2n = 23, NFa = 40; 2n = 23, NFa = 41; 2n = 22, NFa = 39; 2n = 22, NFa = 40. Based on G‑banding method, the determined intrapopulation chromosomal polymorphism in Sicista sp. 1 was defined by two chromosomal rearrangements: tandem translocation involving two biarmed autosomes No 4 and 10 and a pericentric inversion of pair No 6. In the studied sample (n = 13), a stable advantage of heterozygotes was revealed for both structural chromosomal mutations and the chromosomal polymorphism is characterized as balanced or heterozygous. The potential role of the identified polymorphism in chromosomal evolution and adaptive strategy of the species is discussed.

Syndrome del(5)(q14~23),der(10)(p12p15)?add(10)(q26): Case report and literature review

Structural chromosomal mutations are changes that do not modify the number of chromosomes in the cell, but they determine the appearance of abnormal chromosomes. The aim of this study is to report the clinical and cytogenetic history of a patient carrier of a structural mutation with karyotype 46,XY,del(5)(q14~23),der(10)(p12p15)?add(10)(q26) attended by the Genetic Counseling Service of the State University of Londrina. The patient (ABT) is male, had 1 year and 9 months on the day of the examination, normally born, full term (38 weeks) with Psychomotor Development Retardation (PDR) and without other complications. At birth, ABT’s mother was 25 years old and his father was 31 years old. The x-ray, urine analysis, pre- and postnatal ultrasonography, parasitological, ophthalmologic, gastrointestinal and neurological exams do not reveal changes. At the time of cytogenetic examination, the patient underwent surgery for the treatment of esophagogastric reflux and inguinal hernia. Currently, ABT follows up with Pediatrician, Social Worker, Physiotherapist, Speech Therapist, Neuropediatrician, Nutritionist and Ophthalmologist. These findings, particularly PDR, were consistent with the rare syndrome of the 10q + chromosome, since only ten cases of trisomy for the distal segment of the major arm of chromosome 10 (10q +) were described. Excluding the PDR, other characteristics were not found in the trial. Structural chromosomal syndromes represent an opportunity to understand clinical phenotypes and become important in gene mapping, especially when associated with molecular genetic techniques, the next step in diagnostic genetic research. In this way, the patient follows the treatment of the symptomatology.

DNA double-strand break repair in parental chromatin of mouse zygotes, the first cell cycle as an origin of de novo mutation

In the human, the contribution of the sexes to the genetic load is dissimilar. Especially for point mutations, expanded simple tandem repeats and structural chromosome mutations, the contribution of the male germline is dominant. Far less is known about the male germ cell stage(s) that are most vulnerable to mutation contraction. For the understanding of de novo mutation induction in the germline, mechanistic insight of DNA repair in the zygote is mandatory. At the onset of embryonic development, the parental chromatin sets occupy one pronucleus (PN) each and DNA repair can be regarded as a maternal trait, depending on proteins and mRNAs provided by the oocyte. Repair of DNA double-strand breaks (DSBs) is executed by non-homologous end joining (NHEJ) and homologous recombination (HR). Differentiated somatic cells often resolve DSBs by NHEJ, whereas embryonic stem cells preferably use HR. We show NHEJ and HR to be both functional during the zygotic cell cycle. NHEJ is already active during replacement of sperm protamines by nucleosomes. The kinetics of G1 repair is influenced by DNA-PK(cs) hypomorphic activity. Both HR and NHEJ are operative in S-phase, HR being more active in the male PN. DNA-PK(cs) deficiency upregulates the HR activity. Both after sperm remodeling and at first mitosis, spontaneous levels of gammaH2AX foci (marker for DSBs) are high. All immunoflurescent indices of DNA damage and DNA repair point at greater spontaneous damage and induced repair activity in paternal chromatin in the zygote.

A cytogenetic and phenotypic characterization of somatic hybrid plants obtained after fusion of two different dihaploid clones of potato (Solatium tuberosum L.)

Somatic hybrid plants of various ploidy levels obtained after chemical fusion between two dihaploid clones of potato Solanum tuberosum L. have been analysed by cytological, morphological and molecular methods. The hybrid nature of tetraploid and hexaploid plants and the genome dosage in hexaploid hybrids were confirmed by Giemsa C-banding. Tetraploid and hexaploid hybrids showed numerical as well as structural chromosome mutations. The latter occurred mainly in the nuclear organizing chromosome. The tetraploid hybrids were more vigorous than the dihaploid parents as demonstrated by an increase in height, enlargement of leaves, increase in the number of internodes, restored potential for flowering and increased tuber yield. The grouping of tetraploid somatic hybrids into various classes on the basis of leaf morphology revealed that plants with a full chromosome complement were more uniform than aneuploids. Many hexaploid somatic hybrids were also more vigorous than the dihaploid parents and could be grouped into two different classes on the basis of floral colour and tuber characteristics, the differences being due to their different dosage of parental genomes. Most of the tetraploid somatic hybrids showed pollen development halted at the tetrad stage as one of the parental clones contained a S. Stoloniferum cytoplasm. However, one tetraploid plant produced pollen grains with high viability. The chloroplast genome in the hybrid plants was determined by RFLP analysis. All of the hybrids had a cpDNA pattern identical to one parent, which contained either S. Tuberosum or S. Stoloniferum cpDNA. A slight preference for S. Tuberosum plastids were observed in hybrid plants. No correlation between pollen development and plastid type could be detected.

The evaluation of the germinal mutagenic impact of Chernobyl radiological contamination in Hungary

The genetic consequences of radioactive fall-out deposition from the Chernobyl (USSR) accident in Hungary was evaluated as a part of the ongoing programme on the population-based Hungarian Surveillance of Germinal Mutations. The surveillance is based on three groups of indicator conditions: 15 sentinel anomalies (indicators of germinal dominant gene mutations), Down's syndrome (an indicator of germinal numerical and structural chromosomal mutations) and unidentified multiple congenital abnormalities (indicators of germinal dominant gene and chromosomal mutations). Cases with these indicator conditions were selected from the material of the Hungarian Congenital Abnormality Registry. After the diagnostic accuracies were checked, familial and sporadic cases were separated. Only the latter group was evaluated for evidence of new mutations. The analysis did not reveal any measurable germinal mutagenic effects of the Chernobyl accident. Furthermore, there were no significant differences in the rates of these three groups of indicator conditions between regions with higher and lower increased background radiation.

Incidence of legal abortions and congenital abnormalities in Hungary

The annual and monthly distributions of congenital abnormalities and pregnancy outcomes as confounding factors were evaluated in Hungary in reflection of the accident at the Chernobyl reactor. The different congenital abnormality entities and the components of fetal radiation syndrome did not show a higher rate after the Chernobyl accident in the data-set of the Hungarian Congenital Abnormality Registry. Among confounding factors, the rate of induced abortions did not increase after the Chernobyl accident in Hungary. In the 9th month after the peak of public concern (May and June, 1986) the rate of livebirths decreased. Three indicator conditions: 15 sentinel anomalies as indicators of germinal dominant gene mutations. Down syndrome as an indicator of germinal numerical and structural chromosomal mutations, and unidentified multiple congenital abnormalities as indicators of germinal dominant gene and chromosomal mutations were selected from the material of the Hungarian Congenital Abnormality Registry. Diagnoses were checked, familial and sporadic cases were separated and only the sporadic cases were evaluated. The analysis of indicator conditions did not reveal any measurable germinal mutagenic effect of the Chernobyl accident in Hungary.

Variability of DNA content and karyotype in cell cultures of an interdihaploid Solanum tuberosum

Karyological and DNA cytophotometric observations were carried out to follow nuclear events in cell cultures of an interdihaploid potato, genotype H(2)578, 2n=2x=24. The percentage of polyploid cells increased in leaf calluses, but decreased and then remained at a constant level when these cells were cultured in suspension. These suspension cultures did not survive, maybe because they did not become tetraploid. Another suspension culture proliferated with hypotetraploid cells only. Unlike the DNA contents of their interphase nuclei, the karyotypes varied considerably because of numerical and structural chromosome mutations.

Chromosome abnormalities, tumours and developmental disorders (author's transl)

Clonal chromosome disorders occurring or acquired at any postnatal age are often closely related with the origin of tumours. In man the Ph1-chromosome (9; 22) anomaly in CML or the 8; 14 translocation in the African malignant Burkitt Non-Hodgkin lymphoma are, among other cases, prominent examples. On the other hand, constitutive, inherited or novel chromosome anomalies conveyed from the zygote to all tissues of the organism may cause a higher risk for the origin of tumours. Rarely, inheritable minor structural chromosome mutations are known to determine the occurrence of dysontogenetic tumours, as e.g., nephroblastoma, but it is assumed that more such cases will become elucidated in the future. As a special phenomenon, true hydatiform mole is a tumour of the placental tissue due to a disorder of intragenome regulation. Constitutive or numerical structural chromosome anomalies of man are a frequent cause of early or late abortion or of abnormal development and malformation. Despite the predominating principle of selective fetal elimination, a few anomalies such as Down's syndrome, may escape to longer survival due to the relatively mild effects of chromosome 21 triplication. Trisomies which represent in man the most frequent type of chromosome disorders, can be induced, and systematically studied in an experimental model of the mouse. This allows the elaboration of the developmental profiles of all trisomies (and monosomies) of the mouse. Also, the above mentioned principle of selective elimination of abnormal implants can be analysed experimentally. Although the developmental span of a trisomic zygote is limited, there is evidence that cells and tissues isolated from the chromosomally abnormal organism can survive much longer. Thus, haemopoietic stem cells, at least in Ts 12 and 19 of the mouse, can be rescued from trisomic fetuses by transferring them to lethally irradiated adult mice, whose blood forming organs may eventually become permanently repopulated by the trisomic cell lineage. This type of experiments is suited for closer analyses of potential functions vs. defects of chromosomally abnormal cellular systems, e.g., with regard to growth and development.

Incorporation of3H-leucine into acid brain protein of hibernating animals

Spontaneous chromosome reconstructions were examined in bone marrow cells, peripheral blood lymphocytes and epithelial kidney cells from monkeys (Macaca mulatta). In normal monkeys, the chromosome reconstruction frequency was higher in epithelial kidney cells and lower in bone marrow cells. Peripheral blood lymphocytes occupied an intermediate position as regards the chromosome reconstruction frequency. The structural chromosome mutations were characterized mainly by single and twin fragments, with the former ones being predominant. The monkeys examined showed age-associated differences in the frequency of spontaneous chromosome reconstructions.

Isolation of a homozygous X-linked translocation stock with two additional sex-chromosomes in the onion fly Hylemya antiqua Meigen

The onion fly, Hylemya antiqua Meigen, was subjected to irradiation and selection based on observations of fertility and cytogenetics, in order to isolate structural chromosome mutations which might be used for genetic control of this species. To the present time, only a "simple" X-linked translocation could be obtained as a homozygous stock. Sibcrossing was carried out using translocation trisomics (TN + X) obtained from test-crossed translocation heterozygous females (TN) showing numerical nondisjunction. A homozygous stock was obtained with two additional sex-chromosomes. This is a unique case because normally an X-linked translocation can not be made homozygous in the male sex, which normally only carries one X-chromosome.

Synthesis of compound chromosomes from a pericentric inversion in the onion fly Hylemya antiqua.

STRUCTURAL chromosome mutations such as reciprocal translocations1,2, pericentric inversions3 and compound chromosomes4,5 have been considered for the control of insect pests. Their exploitation is based on the capacity to reduce the fertility of a population, and they might be used to introduce a gene into a natural population to render the pest less harmful. This possibility arises from the fact that some structural chromosome mutations confer higher sterility in crosses to wild type, or in the hybrids from such crosses, than in matings within the mutant strain. This property is particularly evident with compound chromosomes which have homologous arms attached to common centromeres rather than to different centromeres. This causes intersterility with wild-type individuals, because all the hybrids carry chromosome duplications and deficiencies. In contrast to studies5–7 in which compound chromosomes were isolated starting from two almost whole arm reciprocal translocations. I have used a pericentric inversion in the onion fly, Hylemya antiqua.

The influence of numerical and structural chromosome mutations on chiasma conditions

The influence of numerical and structural chromosome mutations on chiasma conditions