Homology of G-banded mammalian chromosomes

Linkage relationships of homologous loci and high resolution G-banding patterns of man, mouse, rat, chinese hamster, rabbit, cat, mink, pig, ox and sheep were used for identification of 11 evolutionary conservative autosomal regions. The distributions and inversions of these regions in the ancestor genomes of some phylums have been shown. For example, the regions homologous to human Ip region were detected in cat, mink and rabbit genomes. In the genomes of rodents studied the intraregion inversion was detected. In the ox and sheep genomes the distal end deletions were detected within these regions. In the pig genome these regions were represented solely by disruptions. We supposed that the rapid "catastrophic" chromosomal evolution took place during short time periods of some orders and families separation.     

An improved method for preparing G-banded chromosomes from mouse peripheral blood

We describe here several improvements in the method we originally developed to prepare mitotic chromosomes from peripheral blood of laboratory mice. In addition, we have tried several methods to improve metaphase yield from lymphocytes of the inbred strain DBA/2J, which respond poorly to phytohemagglutinin. The yield of mitoses from DBA/2J cells cannot be improved by enhancing T-cell response using interleukin-2 or by using a different T-cell mitogen, concanavalin A. Metaphase yield from peripheral blood cells of DBA/2J mice can be improved significantly by adding lipopolysaccharide to cultures, probably stimulating B-cell as well as T-cell proliferation.     

The G-banded prophase chromosomes of man.

Using a simple G-banding technique developed in our laboratory, analysis of late prophases enables the visualization of approximately 1000 bands in the haploid set of human chromosomes. These bands have been classified according to the recommendations of the Paris Conference. The increased resolution offered by this technique is likely to be useful in the study of the structure and molecular organization of chromosomes and in identifying minute chromosome defects in birth defects and neoplasia.     

Electron microscopy of G-banded human mitotic chromosomes

Trypsin-treated human metaphase chromosomes stained with Giemsa and uranyl acetate showed clear, reproducible band structures under the transmission electron microscope (TEM). The banding pattern observed with TEM corresponded very closely to the G-band pattern visualized by light microscopy. The TEM images were used for karyotype analyses. Trypsin-treated chromosomes stained with uranyl acetate alone also showed clear G-bands under TEM. Shadow casting in addition to uranyl acetate staining revealed more structural detail of the chromosomes. Chromosome fibers, 200 Å–300 Å in diameter, were observed in the interband regions. Most chromosomes showed the major G-bands under the higher TEM magnification wit0out any trypsin treatment.     

A photographic representation of the variability in the G-banded structure of the chromosomes in the mouse karyotype

Analysis of the mouse chromosomes is becoming increasingly important in many fields of genetic research. It is generally considered that the mouse chromosomes are more difficult to analyse than, for example, human chromosomes which has often led to their misidentification. This article presents a guide to the correct identification of trypsin-Giemsa banded chromosomes from the mouse. The variability in the G-banded structure of each chromosome is presented pictorially together with some suggestions for their unequivocal identification. Since many of the mouse chromosomes have similar banding patterns, those chromosomes which are more frequently misidentified have been compared and contrasted. Finally a summary of the main features for the identification of each chromosome is presented.     

High resolution scanning electron microscopy of plant chromosomes

A preparation technique for high resolution field emission scanning electron microscopy of plant chromosomes is described. The technique was optimized to use standard squash preparations of mitotic and meiotic chromosomes from root tips of barley, wheat, and rye. After light microscopic observation and documentation, the same object can be investigated with a 100-fold higher resolution using a field emission scanning electron microscope. Tilting of the specimens provides a three-dimensional insight into chromosomal structures at different stages of condensation and decondensation. With this technique it was possible to document for the first time at high resolution structures such as the centromeric region, the spindle apparatus and the spindle fibre attachment region. The smallest unit of the DNA packed that can be resolved is a beads on a string-like structure of the nucleofilament (10–15 nm fibre).by D. Schweizer     

The G-banded chromosomes of Roosevelt's muntjac, Muntiacus rooseveltorum

The chromosomes of a female Roosevelt's muntjac (Muntiacus rooseveltorum) captured in Laos have been studied with G-banding. The diploid number is six and the karyotype is indistinguishable from that of the Indian muntjac (Muntiacus muntjak vaginalis).     

Localization of chromosomal RNA in human G-banded metaphase chromosomes

Chromosomal RNA with an 11% dihydropyrimidine content was extracted from human placental chromatin. Under appropriate conditions, this RNA showed wide-spread in situ hybridization to metaphase chromosomes. This included preferential hybridization to the telomeric regions and heterochromatic short arms of acrocentric chromosomes as well as significant hybridization to Q- and G-positive bands.     

A simple procedure for obtaining autoradiographs of G-banded chromosomes

Chromosomal preparations from cells flash-labeled with ³H-dT were Giemsa-banded following trypsin digestion, allowed to air-dry, and then were coated with a layer of 1% Formvar. The slides were subsequently coated with radiographic emulsion (NTB2) and processed for autoradiography. The resulting chromosomes had distinct G-banding and radiographic labeling patterns. Chemographic grain formation in the emulsion, normally caused by Giemsa stain, was prevented by the film of Formvar, allowing a very low background grain level.     

High resolution bands in maize chromosomes by G-banding methods

Summary It was demonstrated that G-bands are unequivocally present in plant chromosomes, in contrast to what had been formerly believed by plant cytologists. Maize chromosomes prepared by an enzymatic maceration method and treated with trypsin or SDS showed clear G-bands spreading along the chromosomes. The most critical point during the G-banding procedures was the post-fixation with glutaraldehyde solution. Banding patterns were processed by using the chromosome image analyzing system and a clearer image was obtained. Gbanding technique and the image manipulation method described here can be applied to many plant species, and would contribute new information in the field of plant cytology and genetics.     

The centromere index and relative length of human high-resolution G-banded chromosomes

Summary The relative length and centromere index were compared in prometaphase and midmetaphase for each human chromosome from five normal men. There were very few differences between prometaphase and midmetaphase chromosomes in these two parameters. Chromosome 7 had a significantly different centromere index between prometaphase and midmetaphase, but no difference in relative length. This was accounted for by significant differences in the relative length of both 7p and 7q between prometaphase and midmetaphase; 7p became relatively less condensed and 7q relatively more condensed with progression from prometaphase to midmetaphase. For chromosome 1, the short arm was significantly longer than the long arm in both prometaphase and midmetaphase, a finding that underscores the structural similarity of this chromosome among the hominids.     

High resolution analysis and differential condensation in RBA-banded human chromosomes

Summary Human prophase, premetaphase, and mid-metaphase chromosomes are prepared and analyzed using the thymidine cell synchronization technique and R-banding patterns (RBA). Haploid sets with 700–1000 bands can be demonstrated. Sequences of chromosomes of different degrees of condensation are helpful for a better understanding and classification of regions of extended chromosomes. A considerable variation in the condensation of parts of homologous chromosomes is reflected in the variability of the arm ratio. This differential condensation of chromosomes is entirely effected by variation of the degree of condensation in AT rich interbands and can be attributed to the degree of labeling by BrdU.     

High resolution R-bands produced in equine chromosomes after incorporation of bromodeoxyuridine

Cell synchronization was used to obtain an adequate percentage of very long chromosomes in equine mitotic spreads. Reported here is our variation, adapted to horse chromosomes, of a method using excess thymidine followed by bromodeoxyuridine incorporation. This technique routinely yields excellent quality cells, predominantly in prometaphase and prophase. Among other differences with the standard technique, this method does not use Colcemid, which, in addition to inhibiting spindle fiber formation, also increases chromosome contraction resulting in thicker and thus fewer bands. Consequently, horse prometaphase chromosomes, which have incorporated BrdU in the late-S-phase, are very long and display a large number of R-bands after the fluorescence-photolysis-Giemsa method. This technique should definitely be useful for the analysis of structural anomalies and the standardization of equine R-bands.     

High resolution mid-prophase human chromosomes induced by echinomycin and ethidium bromide

The antitumor antibiotic echinomycin (EM) was used in combination with ethidium bromide (EB) to induce high resolution mid-prophase chromosomes from amethopterin synchronized blood lymphocytes. With this combination of drugs, trypsin G-banded chromosomes showed over 1200 bands per haploid set in cells having a mid-prophase length of decondensation.     

Localization of single copy DNA sequences on G-banded human chromosomes by in situ hybridization

Recombinant lambda bacteriophage clone H3 containing a human DNA segment of 14.9 kb present in one or two copies per haploid genome was isolated. In situ hybridization to human metaphase chromosomes of the ³H-labeled cloned DNA resulted in highly significant labeling (53% of cells) of band p36 of chromosome 1, such that 22% of all chromosomal grains were located on this region. Hybridization was dependent upon the presence of dextran sulfate in the hybridization mixture and was not affected by repetitive DNA competitor. These results demonstrate localization of a single copy sequence on human metaphase chromosomes.     

Characterization of G-banded chromosomes of the Indian muntjac and progression of banding patterns through different stages of condensation

Muntjac prophase and metaphase chromosomes were G-banded following methotrexate-mediated synchronization of peripheral lymphocytes. Bands and subbands were characterized from prophase through metaphase, and the progression of band patterns from late prophase to mid-metaphase was analyzed. Extended prophase chromosomes exhibited more bands and subbands, a number of which became fused with each other, giving rise to fewer and thicker bands in the condensed metaphase chromosomes. It appeared that the dark bands condensed relatively more than the light bands. Precise delineation of the bands and subbands on extended prophase chromosomes and the usage of a proposed banding pattern nomenclature should aid in better detection and localization of induced chromosomal rearrangements with this extremely useful experimental material.     

High resolution scanning electron micrographic study of dissociated mouse taste cells

New techniques for enzymatic dissociation of mammalian tastecells allowed us to study, for the first time, the morphologyof murine taste receptor cells using high resolution scanningelectron microscopy. Cell shape varied from spindle to bipolarto lamellar, similar to shapes previously described in cellsfrom amphibian taste buds. Cell length varied from 19 to 65µm (39 ± 19 µm), with width averaging 6 ±3.4 µm. A rare picture of the apical microvilli of a tastereceptor cell, and a view of microvilli within a taste pore,suggest that at any given time, five to eight taste cells maybe exposed to the oral cavity. Assuming a cell life-span of10 days, and 50 cells per bud, all of which eventually reachthe taste pore, one can calculate that the average cell is exposedto the oral environment for