Cytological indications of the complex subtelomeric structure.

Research on the subtelomeric region has considerably increased because this chromosome segment (1) keeps the chromosome number constant, (2) intervenes in cancer and cell senescence processes, (3) presents more crossovers than other regions of the genome and, (4) is the site of cryptic chromosome aberrations associated with mental retardation and congenital malformations. Quantitative microphotometrical scanning and computer graphic image analysis enables the detection of differentially distributed Giemsa-stained structures in T-banded subtelomeric segments of human and Chinese hamster ovary (CHO) chromosomes. The presence of high density stain patterns in the subtelomeric region was confirmed using endoreduplicated chromosomes as a model.

Chromosomal aberrations: formation, identification and distribution.

Chromosomal aberrations (CA) are the microscopically visible part of a wide spectrum of DNA changes generated by different repair mechanisms of DNA double strand breaks (DSB). The method of fluorescence in situ hybridisation (FISH) has uncovered unexpected complexities of CA and this will lead to changes in our thinking about the origin of CA. The inter- and intrachromosomal distribution of breakpoints is generally not random.

The underlying structure of the subtelomeric region detected by microphotometrical scanning and chromosome graphic image analysis.

Previous research showed that the microphotometrical scanning of T-banded subtelomeric regions reveals the presence of specific patterns of the Giemsa stain density distributions as detected in chromosomes of normal human lymphocytes and CHO cells. Analyses with this method of the T-banded subtelomeric segments of CHO endoreduplicated chromosomes confirmed that these density patterns replicate in a similar way in sister chromosomes. Besides, the specific removal of portions of the subtelomeric segments appearing as tiny holes located where these density patterns are found suggested that both phenomena are related.

Computer graphics as a tool in cytogenetic research and education.

Scanning microscope photometry has been extensively used for image analysis of nuclei and chromosomes and for automated karyotyping. Color graphics terminals, software development and appropriate data manipulation have expanded the scope of scanning microphotometry so that it is now particularly useful for the quantitative analysis of cell components. We have developed application software for displaying nuclear and chromosome densities on a computer terminal of in the form of pixeled images and pseudo-three-dimensional graphic diagrams, as well as for image transformation, object illumination and rotation to enhance chromatin features.