Scanning electron microscopy of the G-banded human karyotype

The chromosome structure of human metaphases was observed in the scanning electron microscope (SEM) after exposure to G-banding techniques for light microscopy (LM). Individual chromosomes showed an inherent specificity of quaternary coiling. Circumferential grooves along the chromatids demarcated the individual gyres of the coils, which were shown to correspond to the LM G-banding pattern. An increased number of quaternary coils was observed in prometaphase chromosomes, which were shown to be correlated with the high resolution LM bands. We propose that the observation of G-bands relies on LM visualization of quaternary structure by accumulation of Giemsa stain between the coils.     

High-resolution idiogram of Giemsa R-banded human prophase chromosomes

The schematic representation of RHG-banded chromosomes (R-banding was produced by heat denaturation followed by Giemsa staining (RHG) in the 850-band range per haploid set, was prepared showing the relative position, the specific size, and the characteristic staining intensity for each band. To this idiogram was adapted the new International Standard Cytogenetic Nomenclature. Our aim was to produce a realistic idiogram which could help in the preparation of R-banded prophase karyotypes and in the localization of chromosomal rearrangements. A comparative analysis of bands at prophase and metaphase revealed certain aspects of the dynamics involved in chromosome condensation and in R-band organization. The effect of chromosome elongation on the appearance of R-bands within heterochromatic regions has also been discussed.     

G-banded karyotype and ideogram for the North Atlantic right whale (Eubalaena glacialis)

Published cytogenetic data for extant cetacean species remain incomplete. In a review of the literature, we found karyotypic information for 6 of the 13 tentatively recognized species of the suborder Mysticeti (baleen whales). Among those yet to be described is the critically endangered North Atlantic right whale (Eubalaena glacialis). Herein, we describe and propose a first-generation G-banded karyotype and ideogram for this species (2n = 42), obtained from peripheral blood chromosome preparations from a stranded male calf. This information may prove useful for future genetic mapping projects and for interspecific and intraspecific genomic comparisons by techniques such as zoo-FISH.     

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.     

Comparison between the G-banded karyotype of the aoudad (Ammotragus lervia) and sheep (Ovis aries)

Karyotypes of the aoudad and sheep were compared on the basis of G-banded chromosomes at the 450 band level. The common G-banded karyotype showed the homology of all aoudad chromosomes (2n=58) with sheep chromosomes (2n=54) or sheep chromosome arms. The results of cytogenetic investigations suggest that in this case karyotype evolution has led to reduction in chromosome number as a result of centric fusions. The formation of the first metacentric chromosome occurred in the aoudad. The homology of the G-banding pattern in sheep and aoudad suggests the conservation in linear arrangement of genetic material. Thus comparative cytogenetics can be a useful tool in gene mapping.     

State of the art in sheep-goat embryo transfer

Considerable advances have been made in the last 25 yr in sheep and goat embryo production and transfer technology. This presentation covers the procedures used to overcome the variability of ovarian response after treatment with exogeneous gonadotropins, the asynchrony of ovulations, failure of fertilization in females showing a high ovulatory response, and the side-effects of repeated treatments (surgical trauma, gonadotropins and their antibodies). In the ewe, prior antigonadotrophic pretreatment results in a significant gain in ovulation rate due to the elimination of nonresponses and in a two-fold increase in embryo yield. A better comprehension of the relationships between oocyte quality and follicular characteristics after superovulation can be gained using in vitro techniques. This knowledge will subsequently be used for the optimization of embryo production needed for the genetic improvement of livestock and the development of new biotechnologies.     

High resolution G-banded chromosomes of the mouse

High resolution G-banded mouse chromosomes were prepared using an actinomycin D and acridine orange pretreatment protocol, resulting in late prophase mouse chromosomes which reveal over twice the number of bands as compared with mid metaphase. These elongated chromosomes, described here in detail and used to construct a precise schematic representation of the late prophase banding patterns, should be generally useful in high resolution mouse chromosome analysis.     

High-resolution human/goat comparative map of the goat polled/intersex syndrome (PIS): the human homologue is contained in a human YAC from HSA3q23

The genetic and cytogenetic map around the chromosome 1 region shown to be linked with polledness and intersexuality (PIS) in the domestic goat (Capra hircus) was refined. For this purpose, a goat BAC library was systematically screened with primers from human coding sequences, scraped chromosome 1 DNA, bovine microsatellites from the region, and BAC ends. All the BACs (n = 30) were mapped by fluorescence in situ hybridization (FISH) on goat chromosome 1q41-q45. The genetic mapping of 30 new goat polymorphic markers, isolated from these BACs, made it possible to reduce the PIS interval to a region of less than 1 cM on goat chromosome 1q43. The PIS locus is now located between the two genes ATP1B and COP, which both map to 3q23 in humans. Genetic, cytogenetic, and comparative data suggest that the PIS region is now probably circumscribed to an approximately 1-Mb DNA segment for which construction of a BAC contig is in progress. In addition, a human YAC contig encompassing the blepharophimosis-ptosis-epicanthus-inversus region was mapped by FISH to goat chromosome 1q43. This human disease, mapped to HSA 3q23 and affecting the development and maintenance of ovarian function, could be a potential candidate for goat PIS.     

High-resolution chromosome banding studies in Cebus apella,Cebus albifrons,and Lagothrix lagothricha: Comparison with the human karyotype

Karyotypes of three species of South American primates (Cebus apella, Cebus albifrons, and Lagothrix lagothricha) were studied using high-resolution banding techniques, and were compared to the human karyotype. The number of homologies was very high for the three species. Some of the breakpoints implicated in chromosome rearrangements corresponded with human fragile sites. The fragile sites in human chromosomes often correspond with the localization of latent centromeres in the platyrrhines or with large heterochromatic regions that may have been lost or newly added during evolution.     

Blood genetic marker studies of a sheep-goat hybrid and its back-cross offspring

Blood samples from a female sheep-goat hybrid and its back-cross male offspring were tested for electrophoretic variants of plasma albumin, transferrin and esterase, and of red cell carbonic anhydrase, nucleoside phosphorylase, NADH-diaphorase, 'X'-protein, superoxide dismutase, malic enzyme and haemoglobin. Red cells were also tested for blood group antigens. Both animals showed variants that could not be attributed to either sheep or goat alone, thus confirming previous chromosomal data that the female was a genuine sheep-goat hybrid.     

The ancestral karyotype of Carnivora: comparison with that of platyrrhine monkeys

The karyotypes of six species of Carnivora (Mungos mungo, Paradoxurus hermaphroditus, Potos flavus, Mustela furo, Felis serval, and Halichoerus grypus), representative of five different families, were studied and compared. Correspondence between almost all chromosome segments was found, and a presumed ancestral karyotype of Carnivora is proposed. Analogies to human chromosomes are also given, and the results obtained are in excellent agreement with previously published gene mapping data on man and the domestic cat.     

High-resolution structure and strain comparison of infectious mammalian prions

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Blood genetic marker studies of a sheep-goat hybrid and its back-cross offspring

Summary. Blood samples from a female sheep-goat hybrid and its back-cross male offspring were tested for electrophoretic variants of plasma albumin, transferrin and esterase, and of red cell carbonic anhydrase, nucleoside phosphorylase, NADH-diaphorase, 'X'-protein, superoxide dismutase, malic enzyme and haemoglobin. Red cells were also tested for blood group antigens. Both animals showed variants that could not be attributed to either sheep or goat alone, thus confirming previous chromosomal data that the female was a genuine sheep-goat hybrid.     

Further insights into the ancestral murine karyotype: the contribution of the Otomys-Mus comparison using chromosome painting

The African vlei rat, Otomys irroratus, comprises several distinct chromosomal races that may be grouped into two major cytogenetic clades. Recognition of these clades is underpinned by a complex chromosomal rearrangement involving three different autosomes in the unfused state. We have used unidirectional fluorescence in situ hybridization (FISH) of mouse chromosome-specific painting probes to molecularly define the components of this rearrangement as well as to establish the chromosomal homologies between the mouse and the vlei rat genomes. This has allowed for the detection of 41 autosomal segments of conserved synteny. Nine mouse chromosomes were conserved in toto (MMU3, 4, 6, 7, 11, 12, 14, 18, 19) with a further seven (MMU2, 5, 8, 9, 10, 13, 16) showing homology to two discrete regions in the vlei rat genome. Two mouse autosomes (MMU15, 17) correspond to three regions in O. irroratus with MMU1 being the most fragmented showing five sites of hybridization in this species. By mapping these data to published sequence-based phylogenies we are able to confirm most of the published putative ancestral murine chromosomal states. Our data further indicate that MMU15a+ MMU13b+MMU10b+MMU17b was present in the murine ancestral karyotype suggesting an ancestral 2n = 52 rather than the 2n = 54 previously postulated.     

Chromosomal alterations in the karyotype of triticale in comparison with the parental forms

Summary Wheat chromosomes of the primary winter hexaploid and octoploid triticales and of the parental durum and common wheat varieties were studied using morphometric analysis. The size of some heterochromatic segments was shown to change in triticale. Telomeric and intercalary C-bands both increased and decreased in size whereas centromeric bands only increased. The size variability of C-bands in triticale B-genome chromosomes decreased in most of the cases and increased only for several specific C-bands. The C-bands of homologous B-genome chromosomes changed in the same direction in both triticale forms. The changes in size of the C-bands found in R-genome chromosomes detected earlier in these triticale forms (Badaeva et al. 1986) were shown to coincide in their pattern with the size changes of C-bands in homeological B-genome chromosomes. Our data are indicative of regular, directed chromosomal changes in the triticale karyotype.     

Chromosome alterations in the karyotype of triticale in comparison with the parental forms

Summary R genome chromosomes were studied in two forms of primary triticales (hexaploid TPG-1/1-78 and octoploid AD 825) and in their parent rye forms (Secale cereale L. cv. Kharkovskaya 60 and VSKhI, respectively) using the methods of C-banding and morphometric analysis. The size of some heterochromatic segments was shown to alter in the karyotype of triticale. An increase in size was detected approximately in half of all telomeric C-bands; the size of the other C-bands either decreased or did not change. The frequencies of these alterations were 11. The variability in the size of telomeric C-bands in rye chromosomes diminished in both triticales studied. The two triticale forms inherited variants of R genome chromosome polymorphism predominantly with the medium size range of telomeric C-bands. The centromeric C-bands in both triticale forms either enlarged or did not alter. Possible mechanisms responsible for the observed pattern of alterations are discussed.     

High-resolution structure of the soluble,respiratory-type Rieske protein from Thermus thermophilus: analysis and comparison

The structure of the soluble Rieske protein from Thermus thermophilus has been determined at a resolution of 1.3 A at pH 8.5 using multiwavelength anomalous dispersion (MAD) techniques. This is the first report of a Rieske protein from a menaquinone-utilizing organism. The structure shows an overall fold similar to previously reported Rieske proteins. A novel feature of this crystal form appears to be a shared hydrogen between the His-134 imidazole ring ligated to Fe2 of the [2Fe-2S] cluster and its symmetry partner, His-134', one being formally an imidazolate anion, Fe2-(His-134)N(epsilon)(-)...H-N(epsilon')(His-134')-Fe2', in which crystallographic C(2) axes pass equidistant between N(epsilon)...N(epsilon') and normal to the line defined by N(epsilon)...N(epsilon'). This provides evidence for a stable, oxidized cluster with a His(-) ligand and lends support to a previously proposed mechanism of coupled proton and electron transfer. A detailed comparison of the Thermus Rieske protein with six other Rieske and Rieske-type proteins indicates: (a) The cluster binding domain is tightly conserved. (b) The 3-D structure of the 10 beta-strand fold is conserved, even among the most divergent proteins. (c) There is an approximately linear relation between acid-pH redox potential and number of H-bonds to the cluster. (d) These proteins have two faces, one points into the larger complex (bc(1), b(6)f, or other), is involved in the proton coupled electron transfer function, and is highly conserved. The second is oriented toward the solvent and shows wide variation in charge, sequence, length, hydrophobicity, and secondary elements in the loops that connect the beta-sheets.