introduction: heterochromatin consists of dna sequences that are not transcribed, and are repeated in short tandem at heterochromatic regions of chromosomes 1, 9, 16 as well as the distal part of long arm of chromosome y. slightly large tandem repeats at the centromeres of human chromosomes are also considered as heterochromatin regions. the main aim of the present study is to evaluate the hete...

Mouse-human somatic cell hybrids that lose (segregate) human chromosomes produce only mouse 28S ribosomal RNA even when they retain copies of the human chromosomes that contain the genes for 28S ribosomal RNA. In contrast, mouse-human hybrid cells that segregate mouse chromosomes produce only human 28S ribosomal RNA even when they have retained copies of mouse chromosomes that contain the 28S r...

Though reported from a wide variety of human neoplasias, ring chromosomes, in general, are a rare finding in these diseases. The majority were detected by chance when tumors were screened for chromosomal aberrations. In most cases they are a part of highly complex karyotypic alterations and therefore part of unfavourable prognostic factors. However, in some tumor entities (e.g. tumors of mesenc...

Obvious mitotic abnormalities have long been known to occur very commonly in malignant tumours, but as a result of recent improvements in technique much more reliable cytogenetic observations are now possible. Transplantable tumours were the first to be accurately examined, and these were found to consist of populations of cells with variations around a modal (" stemline ") type which differs i...