T.C. Hsu

Localization of heterochromatin in human chromosomes

Heterochromatic regions in chromosomes of man, mainly at the centromeric areas, can be demonstrated with consistency using a special staining procedure. This procedure includes treatments of cytologic

Distribution of constitutive heterochromatin in mammalian chromosomes

Using a special staining technique, a survey of the chromosomes of many mammalian species showed that constitutive heterochromatin is present in all cases and that the heterochromatin pattern appears to be specific and consistent or each chromosome and each taxon. Usually heavy heterochromatin is found in the centromeric areas, but terminal heterochromatin is not uncommon. Occasionally interstitial heterochromatin bands occur. In some species, such as the Syrian hamster and Peromyscus, many chromosome arms are completely heterochromatic.

Populations of repeated DNA sequences in the human genome

Abstract Some properties of the repeated sequences in the DNA of the human genome have been investigated. The human genome consists of 7 × 10 9 base pairs and about 35% of these are repeated sequences. The repeated sequences were divided into families, or groups of families having different reassociation rates. The most rapidly-renaturing repeated sequences constitute 10% of the genome and appear to be closely spaced, possibly in tandem arrangement, while the slowly-reassociating repeated sequences are dispersed. In addition, the rapidly-reassociating sequences were fractionated with respect to the G + C content by thermal elution chromatography. Repetitious sequences, both fast- and slow-reassociating, were found in every arbitrary temperature segment. This indicates the heterogeneity of the repeated sequences since they apparently occurred in the entire spectrum, from very A + T-rich to very G + C-rich varieties. In situ DNA-[ 3 H]RNA hybridization experiments were performed with human cells and [ 3 H]RNA complementary to the various human repetitious DNA fractions. The results suggest that (a) unlike the case of mouse where essentially all centromeric heterochromatins are composed of one DNA family, human heterochromatin is composed of a variety of DNA families, and (b) mapping human chromosomes by nucleic-acid hybridization appears feasible.

Involvement of chromosome 6 in rearrangements in human malignant melanoma cell lines

We analyzed the karyotypes of nine established human malignant melanoma cell lines derived from two female and six male patients. Each of the cell lines had an aneuploid stemline chromosome number. Analysis of G-banded chromosomes identified a number of altered (marker) chromosomes in these cell lines; in all the lines, chromosome 6 was found to be involved in the marker chromosomes. A review of the literature and these cases showed that of 47 cell lines or primary melanoma cells karyotyped, 38 (80.8%) had a marker involving the 6. We believe that the genetic factor determining melanoma initiation is located in the distal segment of 6q. Deletion of this segment or the entire 6q is responsible for the cells (melanoblast or melanocyte) becoming malignant. The proximal segment of 6q and 6p can be involved in marker formation.

The C-band and G-band patterns of Microtus agrestis chromosomes.

The C-band and G-band patterns of Microtus agrestis metaphase chromosomes are described. The C-band pattern reveals constitutive heterochromatin as uniformly intenselystained areas but cannot aid in identifying autosomal pairs. The G-bands revealed by a heat renaturation method (ASG) were compared with those revealed by treatment with three proteolytic enzymes. All procedures yield apparently the same specific pattern of crossbands on the autosomes, and each autosomal pair can therefore be identified by its characteristic pattern. The constitutive heterochromatin of the sex chromosomes stains uniformly with the heat renaturation method but is subdivided into regions with different staining intensities with each enzyme treatment. A G-band karyotype for Microtus agrestis metaphase chromosomes is presented.

Giemsa banding of meiotic chromosomes with description of a procedure for cytological preparations from solid tissues

A procedure is described for preparing solid tissues for Giemsa banding and other cytological applications. Carnoy-fixed tissues are transferred to 60 % acetic acid to dissociate the cells, which are

Relationships between patterns of chromosome banding and DNA synthetic sequences: a study on the chromosomes of the Seba’s fruit bat, Carollia perspicillata

The termination sequences of DNA replication, as visualized in tritiated-thymidine autoradiographs of chromosomes of Carollia perspicillata, appear to follow this order: euchromatin

Induction of Chromosome Banding in Early Stages of Spermatogenesis by Ethidium Bromide

Distinct chromosome banding of early meiotic prophase (leptotene through early pachytene) can he induced in male Chinese hamsters by injecting ethidium bromide and Actinomycin D intratesticularly for 4 hours and making acetic orcein squash preparations from minced testicular tissue. Zygotene pairing apparently starts from chromosome ends.