RESUMO
Premature chromosome condensation (PCC) was induced in order to study the arrangement of muntjac chromosomes in the interphase nuclei of proliferating and resting cells with respect to their polarity and the spatial relationship between them. The data were compared with the situation in in situ fixed and colcemid blocked metaphases. It appears that in rapidly dividing cells almost all G1- and G2 interphase chromosomes exhibit the Rabl type polarized orientation. This pattern still predominates in G0 lymphocytes which may have been arrested at this stage for some months or even years. - The location of the small chromosome Y2 was found to be "central" in normal metaphases but "peripheral" in colcemid blocked mitoses. The behavior in the premature condensed chromosome preparations was intermediate. Measurements of centromere distances between all possible pairs of chromosomes as well as on the relative position of chromosomes in circular spreads revealed no evidence for homologous somatic association during interphase and metaphase or any other suprachromosomal ordering principle. Interphase chromosome orientation seems to be solely the result of chromosome arrangement of the foregoing anaphase. Association between heterochromatic regions or the nucleolus organizers did not substantially influence this pattern. There is no support for speculations that in mammalian cells close proximity of homologous sites is instrumental in functional cooperation.
Assuntos
Cromossomos/ultraestrutura , Cervos/genética , Animais , Corantes Azur , Células Cultivadas , Mapeamento Cromossômico , Feminino , Cariotipagem , Linfócitos/ultraestrutura , Masculino , MitoseRESUMO
Cytogenetic studies of an 8-year-old caucasian girl with typical but mild manifestation of Bloom's syndrome showed a characteristic increase of homologous chromatid translocations and prematurely condensed chromosomes. The average frequency of sister chromatid exchanges (SCE) in lymphocytes with 133 was much higher than in skin fibroblasts with 49. The inter- and intrachromosomal distributions of SCE in lymphocytes were analyzed.
