Lokalisierung von rRNA-Genorten und Sekundäreinschnürungen beiVicia narbonensis undVicia sativa

Sites of 18/25S RNA genes and those of secondary constrictions have been located in metaphase chromosomes ofV. narbonensis andV. sativa by RNA/DNA in situ hybridization and Feulgen staining. InV. narbonensis the rRNA genes are located in median position on one pair of chromosomes, which is the shortest of all in the genome. InV. sativa rRNA genes are located in two pairs of chromosomes. The two heterologous sites differ markedly in the level of labeling. Strong labeling is found in a submedian position of a short pair of chromosomes. Weaker labeling is found in a median position on the longest pair of chromosomes. InV. narbonensis andV. sativa the position of the grain clusters correlate with the position of the secondary constrictions in chromosomes stained by Feulgen. The implications with respect to karyograms ofV. narbonensis andV. sativa known from the literature are discussed.

     

Die intraspezifische Variabilität des heterochromatischen Armes eines Chromosoms bei der GattungCarabus L. (Coleoptera)

The chromosome complement ofC. auronitens Fabr. is 2n _♂=26+XY. One autosomal pair—called A-chromosomes—is relatively long.A-chromosomes consist of a euchromatic and a heterochromatic arm. Labelling of mitotic chromosomes with³H-thymidine shows that replication of the heterochromatic arm continues when it has ended in the euchromatic arm. In males and females the length of the heterochromatic arm varies intraindividually. In 47 of 99 males the heterochromatic arms were heteromorphic. Calculations of the quotient length of the euchromatic/length of the heterochromatic arm have shown that at least 6 different types of the A-chromosome exist. These types differ from each other in the number of heterochromatic sections separated by constrictions. The longest heterochromatic arm observed consisted of 8 such sections. The genetic significance of the heterochromatin in the genus ofCarabus is at present unknown (Zusammenfassung see p.305).      

Further studies on polyploid amphibians (Ceratophrydidawe)

Odontophrynus cultripes Reinhardt and Lutken, 1862 has 22 chromosomes in its diploid complement. Spermatocyte I contained 11 ring bivalents and metaphase II exhibited 11 chromosomes. Odontophrynus americanus (Duméril and Bibron) 1882 has 44 chromosomes in somatic as well as germ cells, these can be sorted into 11 groups of homologues. Metaphase I showed varying numbers of quadrivalents and metaphase II exhibited 22 dyads. Ceratophrys dorsata Wied., 1824 has 104 chromosomes in somatic and germ cells; these 104 chromosomes comprise 8 each of 13 kinds of homologues. The spermatocyte I contained ring octovalents and other multivalents, and metaphase II 52 chromosomes. The above findings indicate that evolution by polyploidization occurred in South American frogs belonging to the family Ceratophrydidae.This work was supported by a grant (GM-14577-01) from the National Institute of General Medical Sciences U. S. Public Health Service.     

Chromosome studies of the cultured cells of two species of side-necked turtles (Podocnemis unifilis and P. expansa)

The diploid chromosome number of two species of sidenecked turtles (Podocnemis unifilis and P. expansa) was found to be 28. Under normal culture conditions, half of the chromosomes of P. unifilis consistently show one or two clear secondary constrictions. In P. expansa, the incidence of cells with chromosomes bearing secondary constrictions and the number of such chromosomes per cell are less. Cells of two P. unifilis cell lines maintained a normal diploid karyotype for two years following their initiation. Then one cell line shifted to a hypodiploid mode of 27 and half of the population of the second line became pseudodiploid, the other half remaining diploid. A single six-month-old cell line from P. expansa has maintained a normal diploid mode through 10 passages.Supported in part by grant-CA 08737 from the National Cancer Institute.     

Q-bands in Lilium and their relationship to C-banded heterochromatin

In L. pardalinum, narrow bands of quinacrine fluorescence are distributed throughout the chromosomes. These vary in intensity from dull to bright, and their constant pattern allows all chromosomes to be recognized. Bright bands occur at some centromeres, and near all three nucleolar constrictions. In L. longiflorum, similar Q-bands occur along chromosomes, but they are less distinctive and their pattern does not closely match that of L. pardalinum. Also, L. longiflorum does not have bright regions at or near primary and secondary constrictions. Most Q-bands do not coincide with dark Giemsa C-bands, except for the bright nucleolar and centromeric regions in L. pardalinum. All C-banded heterochromatin stains identically after SSC pretreatment, dark with Giemsa and bright with quinacrine.— The many Q-bands of varying intensity, wide distribution and constant pattern, unrelated to C-bands, may be analogous to mammalian Q-bands. Such universality is expected if Q-bands area fundamental component of chromosome architecture.     

Supernumerary chromosomes in a Rhamdia hilarii population (Pisces,Pimelodidae)

A study was conducted on the chromosomes of a Rhamdia hilarii (Pisces, Pimelodidae) population. The results suggest that the basic chromosome number is 2n=58, with numerical variation up to a limit of 2n=63, due to the presence of supernumerary chromosomes which seem to be mitotically stable. These chromosomes are metacentrics and can be different in size. The C-banding pattern, showing heterochromatin especially in both telomeric regions, permits their identification in the karyotype. The NORs are located on secondary terminal constrictions on the short arm of a pair of subtelocentric chromosomes. However, there may be heteromorphism in the size of the secondary constrictions and, consequently, in the size of the NORs.     

Die kinetische Organisation der Lepidopteren-Chromosomen

In monokinetic chromosomes half of the recombinations from reciprocal translocation are expected to be lethal owing to the formation of bikinetic and akinetic chromosomes. In holokinetic chromosomes all reciprocal recombinations should be viable, because all again are holokinetic. This difference can be used as a tool other than the study of fragment behaviour to decide which type of chromosome is present in an animal species. — Pieris brassicae males X-rayed with 6,000 r units and mated to normal females gave in F₁ only 19.9% lethal zygotes (14.7% of which dying late) as compared to a control mortality of about 7.7%. Among the hatched male caterpillars cytologically tested in the last larval instar 64.9% contained in their spermatocytes 1 to 4 heterozygous translocation rings or chains consisting of from 4 to 14 chromosomes. Translocations of similar frequency and even greater complexity have been observed in preliminary experiments on Philosamia cynthia. — The discrepancy between these results and those on species with monokinetic chromosomes (Drosophila, Phryne etc.) where very high zygotic lethality is observed at comparable Röntgen doses is proof of the holokinetic nature of Pieris and Philosamia chromosomes. Together with earlier results on Bombyx mori by Astaurow and Frolowa and the cytogenetic studies especially by Seiler sufficient proof exists to conclude that all Lepidoptera have holokinetic chromosomes. — A survey of the known groups of organisms with chromosomes of this type leads to the assumption that holokinetic chromosomes must be derived from monokinetic ones. The problems connected with this change in kinetic organisation of chromosomes are discussed.

---

---

Herrn Professor Dr. J. Seiler ist diese Arbeit in herzlicher Dankbarkeit für in mehr als 40 Jahren gewachsene Freundschaft zu seinem achtzigsten Geburtstag gewidmet worden.

---

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Differential staining and chromatin packing of the mitotic chromosomes of the newt Triturus cristatus

Mitotic metaphase chromosomes of cold-treated Triturus cristatus show a characteristic pattern of constrictions, most of which lie close, though not immediately adjacent, to the centromeres. The chromatin in these cold-induced constrictions stains intensely with Giemsa. Cold-treated spermatogonia show spiral structure throughout the metaphase chromatids; the packing of chromatin fibrils is much tighter in the constricted regions than elsewhere, and the gyres in the constricted regions are narrower and of shorter pitch.     

Three euchromatic DNA sequences under-replicated in polytene chromosomes of Drosophila are localized in constrictions and ectopic fibers

We examined three regions of under-represented euchromatic DNA sequences (histone, Ubx, and 11 A), for their possible correlation with euchromatic constrictions in polytene chromosomes of Drosophila melanogaster. Cloned sequences were hybridized to filters and to chromosomes prepared for light microscopy. Under-represented sequences hybridized to DNA within constrictions and in ectopic fibers. In contrast, adjacent sequences that were fully endoreplicated in the Ubx and 11A regions in polytene cells hybridized to sites just adjacent to their respective constrictions. For one region (Ubx), sequences under-represented in salivary gland cells were fully endoreplicated in fat body cells. For this particular region, the morphology of the polytene chromosomes differs between these two cell types in that the specific constriction is absent at this region in fat body polytene chromosomes, thus strengthening the correlation between under-representation and chromosome constrictions. Although all three sequences are in regions that have been classified by others as intercalary heterochromatin, we detect no common functional or sequence organizational feature for these examples of under-represented DNA. We suggest that the lower efficiencies of the replication origins, or special regions of termination at these sites, are the primary cause of the under-replication, and that this under-replication is sufficient to confer the properties of intercalary heterochromatin.     

Chromosome analysis and DNA homology in threePicea species,P. mariana,P. rubens,andP. glauca (Pinaceae)

A detailed karyotype analysis was made on the somatic complement ofPicea rubens andP. glauca. B-chromosomes were observed in someP. glauca populations. The karyotypes are generally asymmetrical with most of the chromosomes having median to median-submedian centromeres.Picea glauca chromosomes 2, 3, 7, and 8 have secondary constriction on their short arm and chromosome 10 has a secondary constriction on the long arm. Chromosome 3 was the most easily identifiable, as it has two secondary constrictions located on the short arm. InP. rubens, all the chromosomes but chromosomes 8 and 9 have one to four distinctive secondary constrictions. In general, the diagrammatic comparisons show a high degree of similarity amongP. mariana, P. rubens, andP. glauca. GenomicP. mariana probe strongly hybridized to dots of genomic DNA fromP. rubens andP. glauca indicating that there is a high sequence homology among these three species. The synchronizing agent, hydroxyurea was used at different concentrations to enhance the mitotic index of cell suspensions derived from embryogenic cultures. Hydroxyurea at 1.25 mM increased significantly the mitotic index. An increase of hydroxyurea from 1.25 mM to 5 mM and 10 mM resulted in a steady decrease of mitotic index.     

In situ localization and characterization of different classes of chromosomal DNA: acridine orange and quinacrine mustard fluorescence

In situ denaturation of metaphase chromosomes with alkali results in a shift from green to yellow, orange, brown and red fluorescence with acridine orange, indicating increasing denaturation of chromosomal DNA. The kinetics and characteristics of denaturation are described. Mouse and Microtus agrestis chromosomes denature uniformly but human cells show sequential denaturation. With increasing concentrations of alkali, the secondary constrictions in chromosomes 1, 9 and 16 are the first, and the distal half of the Y chromosome the last, to become denatured. — Reassociation of chromosomal DNA occurs within seconds after the start of incubation in salt solution. Areas containing repetitious DNA, e.g. mouse centromeres, fluoresce much more strongly than other regions with acridine orange after prolonged reassociation. Since human and Microtus centromeric regions behave similarly, it is proposed that they, too, contain repetitious DNA. — Reassociation treatment leads to enhancement of bright quinacrine mustard fluorescence in regions already bright before treatment. Furthermore, regions containing repetitious DNA, e.g. the secondary constrictions in human chromosomes 1, 9 and 16, whose fluorescence is dull before treatment, turn bright after reassociation. — The methods of fluorescence analysis of mammalian chromosomes with acridine orange and quinacrine mustard permit the localization and study of different classes of chromosomal DNA.     

Chromosome banding in the genusPinus

Somatic chromosomes (2n=24) ofPinus luchuensis Mayr at metaphase were observed by fluorescent banding methods with chromomycin A₃ (CMA) and DAPI. CMA-bands appeared at the interstitial and/or proximal regions of nearly all chromosomes. DAPI-bands appeared at the interstitial and/or centromeric regions of nearly all chromosomes, and pairs of DAPI-dots appeared at the centromeric regions. Each homologous pair of chromosomes in the chromosome complement was identified by the CMA and DAPI fluorescent banding patterns. The interstitial CMA-bands were mostly localized at the secondary constrictions of the Feulgen-stained chromosomes. The fluorescent banding pattern ofP. luchuensis was very similar to that ofP. thunbergii, but was different from that ofP. densiflora.     

Giemsa C-banded karyotypes and taxonomic relationships of some North AmericanAllium species and their relationship to Old World species (Liliaceae)

The somatic karyotypes of six North AmericanAllium species and the EuropeanA. scorzonerifolium have been investigated using a Giemsa C-banding technique. All species have a chromosome number of 2n = 14. InA. scorzonerifolium and the three North American speciesA. dichlamydeum, A. fibrillum andA. unifolium C-bands are restricted to two pairs of nucleolar chromosomes. Each chromosome has a band proximal to the nucleolar constriction and a positively banded satellite. InA. acuminatum, in addition to the bands associated with the nucleolar constrictions, all chromosomes also have pericentromeric bands.A. cernuum exhibits a distinctive banding style: two chromosome pairs with bands adjacent to the nucleolar constrictions and four pairs with telomeric bands on their short arms. In the karyotype ofA. geyeri neither C-bands nor nucleolar chromosomes were found.—A comparison of the banding styles together with other cytological and morphological characters of these species with old world members ofAllium reveals:A. cernuum closely resembles species within subgenusRhizirideum, whereas the other species studies exhibit many similarities with subgenusMolium. Their sectional grouping and their relationships with Old World species are discussed.     

Taxonomy of the genusBrimeura (Hyacinthaceae)

A taxonomic reevaluation of two little-knownBrimeura taxa,B. fontqueri (Pau)Speta andB. duvigneaudii (L. Llorens)Rosselló et al., has been made.Brimeura fontqueri, described from the Iberian peninsula, has been put into synonymy ofB. amethystina (L.)Salisb., since it could not be distinguished on morphological, anatomical or cytogenetic grounds.Brimeura duvigneaudii, from the Balearic Islands, is closely related toB. amethystina and has 2n=28 chromosomes. It differs from the latter by its naked bulbs lacking dark cataphylls, and its narrower leaves and whitish corollas. Accessory chromosomes are reported for the first time in the genus. Karyological instability (with chromosome numbers ranging from 2n=28 to 42) is reported for a population ofB. fastigiata (Viv.)Chouard. A key to the recognized taxa ofBrimeura is provided.     

The location of ribosomal cistrons (rDNA) in chromosomes of the rat

In situ hybridization of ³H-labelled ribosomal RNA to the chromosomes of rat bone marrow cells revealed that clusters of ribosomal cistrons (rDNA) are located in the secondary constrictions of chromosomes No. 3 and 12 and near the centromere of chromosome No. 11, both associated with the late DNA-replicating regions. They were not found in Nos. 1, 2, 13, 19, 20, and the Y chromosome.     

Hierarchy of organization in eukaryotic chromosomes (a review)

Summary Several models of macromolecular arrangements in eukaryotic chromosomes have been proposed during the past fifteen years. Many of the models are consistent with physical and chemical data on the molecular components of chromosomes, and a few have the appearance of meeting the requirements for cytological organization in chromosomes. However, one of the most frustrating problems in developing a working model is to provide a scheme that fits genetic function while satisfying the structural parameters. This has not yet been achieved.Although emphasis in this review has been placed on uninemic and polynemic models, alternatives, such as a bineme, for example, remain. It is clear, moreover, that the issue can be resolved only through continued efforts to make direct observations of chromosomes with light and electron microscopy coupled with the additional tools ofX-ray analysis and analytical biochemistry. A recent analysis byWray andStubblefield (1969) has led to a rather innovative model of the chromosome, and exemplifies the kind of approach needed to clarify the phenomenon. Furthermore, analyses of meiotic chromosomes may provide valuable insight for relating organization to genetic function (cf Maguire, 1966 andBraselton, pers. comm). Of particular interest are mutation events as related to subchromatid organization, and the reorganization of chromosomal fibrils during early meiotic stages. At present, and as a generalization, the evidence points more strongly toward at least a binemic arrangement of chromosomal subunits than toward a uninemic one.     

Revision of SAT chromosome number in Triticum monococcum with respect to nucleolar organizers activity

Summary Six varieties of Triticum monococcum were analysed by means of the nucleolar test; i.e., estimation of the maximum number of primary nucleoli per nucleus. All of the varieties exhibited 4 primary nucleoli in telophase and early interphase. Following detailed karyological analysis four SAT chromosomes in all six karyotypes were found in accordance with the maximum nucleolar number. Secondary constrictions and microsatellites were localised on the short arms of chromosome pairs 3 and 5. A new order of the chromosomes in the idiogram of Tr. monococcum is proposed.     

Karyotype analysis and heterochromatin differentiation with Giemsa C-banding and fluorescent counterstaining inCephalanthera (Orchidaceae)

Detailed studies of the chromosomes of the three Austrian species of the genusCephalanthera showed them all to have basically similar karyotypes. BothC. damasonium (2n = 36) andC. longifolia (2n = 32) have three large and several classes of smaller chromosome pairs. The karyotype ofC. rubra (2n = 44) is composed of four large and several groups of smaller pairs. The heterochromatin in these species amounts to about 10% of total karyotype length. All the chromosomes have Giemsa-positive centromeres, but only a few have intercalary or terminal bands. Using differential fluorescent staining with DAPI/actinomycin D, quinacrine/actinomycin D (both A-T specific), and chromomycin A₃/distamycin A (G-C specific) three different types of major heterochromatic bands can be characterized in respect of their satellite DNA composition: highly A-T rich, slightly A-T rich, and very G-C rich. The chromosomes ofC. longifolia contain more A-T rich C-bands than those ofC. damasonium, while the latter's have more G-C rich heterochromatin. In both species several C-bands appear as secondary constrictions or gaps in the Feulgen-stained chromosomes, but most likely, in each species there is only one pair of chromosomes where the secondary constrictions function as nucleolus organizing regions. No major intraspecific variation could be observed except on one small chromosome pair ofC. longifolia which had a heteromorphic C-band in most individuals. Possible pathways of karyotype evolution involving polyploidy and Robertsonian events are discussed.     

Polytene chromosomes from ovarian pseudonurse cells of the Drosophila melanogaster otu mutant

Certain mutant alleles of the otu locus in Drosophila melanogaster produce abnormal nurse cells in the ovaries. These cells are called pseudonurse cells (PNC), since they generate polytene chromosomes instead of endopolyploid ones and do not normally have an oocyte to nurse. The banding pattern of polytene chromosome 3 from the salivary glands (SG) and from PNCs of homozygous otu ¹ females was compared and a detailed photomap of PNC chromosomes with different degrees of polyteny is presented. The banding pattern was found to be strikingly similiar in the two tissues. The puffing pattern of the PNC chromosomes was also studied and the function of the PNC chromosomes is discussed. No constrictions or breaks were found in the PNC chromosomes which seems to indicate that these sites, which are known to be underreplicated in the SG chromosomes, are equally replicated along with the rest of the chromosomes in the PNC nuclei.     

Note on the chromosomes of Nicotiana plumbaginifolia Viviani

The centromere position on the chromosomes of three European stocks of Nicotiana plumbaginifolia (2n=20) was determined by investigating in root tip mitoses the shape of the chromosomes during congression and polar movement and during C-metaphase. One pair of chromosomes is subtelocentric and 9 pairs are acrocentric. Some chromosomes mimic (sub-)metacentrics by having noncentric constrictions. A recently published (A. Villa; Genetica 64: 145–148, 1984) idiogram of one of the stocks is commented on.