Interstitial C-bands Research Articles

Relationship of mouse minor satellite DNA to centromere activity

Chromosomes from a female mouse cell line were identified by Q-banding prior to in situ hybridization with 3H-labeled mouse minor satellite (satellite II) DNA. No cell was found in which every chromosome was labeled, but grain counts showed that every active centromeric region had minor satellite sequences. In the mouse T (10;13)199H translocation, the breakpoint was within the minor satellite array, leaving clusters of minor satellite at the C-bandless active centromere of the 13(10) chromosome and at the interstitial C-band of the 10(13) chromosome, which is not associated with centromeric activity. In a mouse A9 (L-cell derived) marker chromosome with one terminal and two interstitial C-bands, only the terminal C-band was adjacent to an active centromere, but minor satellite DNA was present at all three sites. Minor satellite DNA was not detected on the Y chromosome, although the presence of a small amount of divergent satellite sequences on this chromosome could not be ruled out.

Distribution of chromosomal polymorphisms in three subspecies of squirrel monkeys (genus <i>Saimiv</i><i>i</i>)

The presence of nucleolar organizer regions (NORs) and C-band polymorphisms has been examined in three subspecies of squirrel monkeys, Saimiri sciureus sciureus, S. boliviensis boliviensis, and S. boliviensis peruviensis. Pericentric inversions in chromosomes 15 and 16 were also examined in the three groups. Chromosome 15 was acrocentric in S. s. sciureus and submetacentric in S.b. boliviensis and S.b. peruviensis. Chromosome 16 was acrocentric in S.s. sciureus and S.b. boliviensis while being submetacentric in S.b. peruviensis. There was a significant difference in the distribution of the C-band polymorphisms on chromosomes 5 and 14 in the three groups, as determined by Chi-square analysis, while no difference was observed in the distribution of the NOR polymorphism on chromosome 2. The NOR polymorphism and the interstitial C-band polymorphism of chromosome 14 were found in all three groups; the C-band polymorphism of chromosome 5 was found only in S.s. sciureus. Twelve pedigreed families were examined. Pedigree analyses were consistent with codominant inheritance of each polymorphism. The results of these cytogenetic studies in squirrel monkeys are pertinent to genetic management and research protocols.

Pairing competition between identical and homologous chromosomes in autotetraploid rye heterozygous for interstitial C-bands

Pairing competition between identical and homologous non-identical chromosomes is analysed in autotetraploid metaphase I cells of rye where one pair of identical partners bears an interstitial C-band in the long arm of chromosome 6R whereas the other pair of identical partners lacks such a C-band. This makes it possible to study pairing preferences in two distinct regions of the same chromosome arm. A significant excess of associations involving homologous partners is always observed in the proximal segment (from the centromere to the C-band), whereas a good fit with the expected random ratio, or else identical pairing preferences, is found in the distal segment (from the C-band to the telomere). Differences in the processes of pairing and chiasma formation in 6RL, and/or a readjustment in the pattern of chiasma distribution due to heterozygosity for the interstitial C-band as a result of homologous nonidentical pairing, may be responsible for the different behaviour detected in the two regions of the marked arm.

Identification by C-banding of two human prostate tumour cell lines, 1013L and DU 145.

Two human prostate carcinoma cell lines are easily distinguished by C-banding. DU 145 has one metacentric chromosome with a large centromeric band, 1 metacentric and 2 acrocentric chromosomes with interstitial C-bands. The Y chromosome was present in 48% and 42% of the cells at passages 83 and 106, respectively, whereas in 1013L only one metacentric chromosome contained distinct extra C bands--one at the centromere and one interstitially. The Y chromosome was present in 72% of the cells at passage 15 and in 20% at passage 22, but by passage 44 it had disappeared. Karyotype analysis using G-banding revealed that DU 145 had retained several of its original markers, and demonstrated multiple marker chromosomes in 1013L.

Fluorochemical characterization of C-bands in the chromosomes of Nigella damascena(Ranunculaceae)

Summary After the C-banded interphase nuclei and mitotic metaphase chromosomes of Nigella damascena were sequentially stained with CMA and DAPI, the centromeric C-dots of all chromosomes displayed bright fluorescence with DAPI and the interstitial C-bands located at the secondary constricted regions of three pairs of metacentric chromosomes displayed fluorescence with CMA. The other C-bands were also brightly fluoresced with either CMA or DAPI.

Studies on chiasma distribution and chiasma movement in Zoniopoda tarsata (Orthoptera: Romaleidae)

A sample of 27 males of Zoniopoda tarsata from Argentina was studied cytologically. The three largest autosomal pairs and the X were characterized by the presence of interstitial C-bands. Chiasma position relative to the bands was analyzed at diplotene and diakinesis. The frequency of interstitial, terminal and total chiasmata per cell was studied for the whole autosomal bivalent set, analysing the variations between stages and among individuals. The comparison of interstitial chiasma frequencies between stages and among individuals and the study of chiasma position relative to the bands in pairs 1, 2 and 3 indicated that chiasma distribution varied from diplotene to diakinesis. Therefore, terminalization does exist in this species and the movement may occur towards the centromere. The frequency of terminal associations at diplotene showed a high negative correlation (r=-0.89; p<10-5) with the number of interstitial chiasmata. This correlation would not be expected if the two kinds of association were produced by different (independent) mechanisms. Consequently, terminal associations were considered genuine chiasmata. The correlation between interstitial and total chiasmata was very much lower then the former (r=0.39; p=0.04). This fact, besides the relatively low variation for chiasma number, observed among individuals suggests that in this species the number of interestitial chiasmata, which are the most important in controlling the genetical recombination, is mainly regulated by changes in chiasma distribution, while variations in total chiasma frequency are of much lower magnitude.

In situ nick translation distinguishes between C-band positive regions on mouse chromosomes.

In situ nick translation of mouse metaphase chromosomes by non-radioactive detection means and DNase I digestion followed by Giemsa staining were used to analyse the DNase I resistance of two different C-band positive regions. These were the centromeric heterochromatin of acro- and metacentric chromosomes and an interstitial C-band on chromosome 1 of wild mice, IS(HSR;1C5D)1Lub. Whereas the centromeric heterochromatin was clearly resistant to DNase I, the interstitial C-band showed very high DNase I sensitivity. Among centromeric C-bands, the heterochromatin in Robertsonian fusion biarmed chromosomes was more resistant to DNase I action than was the centromeric heterochromatin of the acrocentric chromosomes.

Genetic variability in Muscari comosum L. (Liliaceae). II. Characterization and effects of the polymorphic variants of chromosome 2 on chiasmata formation

Muscari comosum L. (Liliaceae) displays a striking chromosomal polymorphism in the second largest chromosome. This polymorphism involves four cosmopolitan types. Two of these are shorter than the other two homologues. One of these is submetacentric (SSM) and the other is subtelocentric (SST). The two longer types also include a submetacentric (LSM) and a subtelocentric (LST) morph. Each of the two submetacentric chromosomes has one interstitial C-band in the short arm and each of the two subtelocentric morphs has an interstitial C-band in the long arm. The change of position of this interstitial C-band is most easily explained by a pericentric inversion. Furthermore, all four types of chromosome 2 have a centromeric C-band, while the two subtelocentrics have an additional terminal C-band in the long arm. The variability in the size of the second chromosome is most likely the consequence of an unequal interchange or an insertional translocation. The meiotic behaviour of the chromosome 2 bivalents in individuals heterozygous for the pericentric inversion is characterized by normal pairing between homologues with no inversion loops, though asynapsis was present in some meiocytes. Chiasmata are absent in two regions of chromosome 2 bivalents in these heterozygotes in which they regularly form in both classes of homozygotes. In individuals heterozygous for the long morphs of chromosome 2 the bivalents again showed normal pairing at pachytene, with chiasmata again absent in some regions in which they normally form. The net result is that homozygotes have significantly higher chiasmata frequencies than hterozygotes. Key words: genetic variability, chiasma formation, Muscari.

Interstitial chiasmata and centromere orientation in heterozygotes for a translocation in rye

The meiotic behaviour of plants heterozygous for translocation T242W of rye (involving 2RL and 6RL) and an interstitial C-band in 2RL has been analyzed. Chain and frying pan quadrivalents predominate. The following results have further been obtained: (i) double chiasmata occur in the interstitial segment carrying the C-band; (ii) from the frequency of being bound at metaphase I and the frequency of recombinant chromosomes at anaphase I, estimates of chiasma frequencies (and chiasma interference) in interstitial segments have been derived; (iii) estimates of the recombination fraction between the interstitial C-band and the translocation breakpoint have been obtained from offspring analysis; (iv) there is a difference in the frequency of alternate orientation between configurations with and without interstitial chiasmata (adjacent-2 has not been observed and a small but significant excess of alternate vs. adjacent-1 coorientation appears). Without intersitial chiasmata, alternate orientation predominates. The possible reasons for these differences are discussed. Key words: Secale cereale, translocations, chiasma frequency, centromere orientation.

Mapping of a chromosome pairing gene and 5S rRNA genes in Triticum aestivum L. by a spontaneous deletion in chromosome arm 5Bp

A deletion in the p arm of chromosome 5B of Triticum aestivum L. cv. Chinese Spring was identified by C-banding during the production of disomic substitutions of 6B of Aegilops longissima Schweinf. et Muschl. for chromosome 5B of cv. Chinese Spring. The deletion was terminal with a breakpoint just proximal to the interstitial C-band. The degree of metaphase I chromosome pairing in plants homozygous for the deletion indicated that the chromosome pairing promoting gene known to be in the p arm of chromosome 5B is located in the deleted portion of that arm. Additionally, all of the 5S ribosomal RNA genes known to exist on arm 5Bp were mapped to this deleted portion.Key words: C-banding, 5S rRNA genes, Triticum, Aegilops chromosome aberration.

Intraspecific variation in C-banded chromosomes of Aegilops comosa and Ae. speltoides

Intraspecific variation in C-banding patterns can be used to differentiate subspecies of Ae. comosa, i.e. eu-comosa and heldrechii, but not those belonging to Ae. speltoides. Among the eu-comosa accessions, comosa E appears to possess a totally different karyotype as well as banding pattern. Two contrasting types of polymorphic changes were found. The first and more common type, observed in the 2 subspecies of Ae. speltoides and 2 accessions of Ae. comosa ssp. eucomosa, involved variation in C-band size and presence or absence of interstitial, terminal and proximal bands within a basic recognisable pattern. The second type involved complete repatterning of C-bands and could be seen in Ae. comosa where the ssp. eu-comosa has predominantly interstitial C-bands in contrast to centromeric and telomeric bands in the other ssp. heldrechii. Furthermore, the extent of polymorphic variation was found to vary between chromosomes of Ae. speltoides. That polymorphic changes have occurred without loss of fertility in hybrids between subspecies of each of the 2 species confirms that these sorts of changes have no effect on chromosome pairing or fertility. Polymorphic changes appear to be widespread within and between diploid Aegilops species and their non-random distribution seem to suggest that these changes could perhaps be intimately associated with the processes of speciation and subspeciation.

Constitutive heterochromatin polymorphism in Lagothrix lagothricha cana, Cebus apella, and Cebus capucinus.

We describe the C-bands in the karyotypes of Lagothrix lagothricha cana, Cebus apella and Cebus capucinus. The C-banding patterns show both a high degree of polymorphism as well as the presence of terminal and interstitial C-bands. Varying amounts of heterochromatin result in dimorphism of some chromosome pairs. The high incidence of chromosome rearrangements found in the Cebidae may be due to the presence of terminal and interstitial C-bands.

Chromosome C-banding patterns in Spanish Acridoidea

The karyotypes of 47 Spanish acridold grasshoppers have been analyzed by means of C-banding in both mitotic and meiotic cells. The most frequent location of C-heterochromatin occurs in centromeric and telomeric regions whereas interstitial C-bands are very scarce. No clear relationship between similarities in C-banding patterns and taxonomic proximity has been found. Negatively heteropycnotic regions are described; their uniform location and distribution suggest that they could represent a functional chromosome structure as nucleolar organizers.

Metaphase I bound arms and crossing over frequency in rye

Using a Giemsa C-banding procedure it has been possible to identify at meiosis three chromosome pairs of a local Spanish rye cultivar. Two of these chromosomes (3 and 5) were heterozygous for an interstitial C-band in the long arm and the other (chromosome 7) was heterozygous for a telomeric C-band, also in the long arm. From the frequency of being bound at metaphase I and the frequency of recombined chromatids at anaphase I in the arms considered, estimates of actual chiasma frequencies have been derived. The results have been compared with those obtained in a Fl between two inbred lines. It is concluded that: (i) Although the frequency of bound arms analyzed was similar in all cases, the chiasma frequency was higher in the cultivar than in the Fl plants. Cultivar plants showed a variation in chiasma frequency for the bivalent arms studied which was correlated with the frequency of bound arms per cell, indicating that the estimation for chiasma frequency by means of bound arm frequency has an error that increases with increasing number of bound arms per cell, (ii) Evidence of chiasma terminalization has not been found, (iii) It is suggested that the different rye chromosomes have different chiasma localization patterns, which, in turn, are related with the chiasma frequency.

CENTROMERIC BANDING IN MAIZE

A modified Leishman C-banding technique is described which can produce a complete set of centromeric bands on the somatic metaphase chromosomes of maize (Zea mays L.). Several interstitial (minor) C-bands, additional to those revealed by the conventional C-banding method, were observed. Centromeric bands were produced only after both an alkali and salt treatment were incorporated into the treatment schedule and a subsequent water rinse was omitted. Apparently, the combined action of alkali and salt treatments provided a positive contribution to the centromeric regions which otherwise remained unstained using the standard C-banding technique.

Regularities and restrictions governing C-band variation in acridoid grasshoppers

C-band patterns have been analysed in embryonic neuroblast chromosomes of 23 Australian species of acridoids. All of them showed paracentromeric C-bands but these varied considerably in size both within and between species. Many of them also showed interstitial C-bands in from 1–5 members of the haploid complement and in two cases (Atractomorpha similis and Genus nov. 95 ochracea) larger numbers of interstitial bands were present. Terminal C-bands were the least common though again when present they could be found in 1–6 members of the complement except in the cases of A. similis and Genus nov. 95 ochracea where still larger numbers occur. In 5 of the 23 species the megameric chromosome pair was distinctively C-banded. The B-chromosomes found in 3 of the species were also strikingly different in C-band characteristics compared to the standard A-chromosomes. Differences in the number of very small chromosomes present in different species clearly cannot be explained in terms of differences in their C-band content. Neither are differences in genome size simply related to differences in the total amount of C-band material indicating that changes in the size of the genome in this group have involved alterations in both eu and heterochromatin content. Finally similar amounts of C-band material may be distributed throughout the complement in very different ways in different species.

Nuclear protrusions in malignant tumours with large abnormal chromosomes: observations on C-banded preparations.

The appearances are described in 4 human tumours having nuclear protrusions associated with large abnormal chromosomes. In C-banded preparations, chromocentres were seen in the protrusions only where interstitial C-bands were present on the long arm of the abnormal chromosome, providing evidence that the protrusions are indeed formed by the long arms.

The G- and C-Bands in Relation to Robertsonian Polymorphism in the Malayan House Shrew,Suncus Murinus(Mammalia, Insectivora)

SUMMARYThe G-bands establish that 4 pairs of acrocentric autosomes are ivolved in the Robertsonian translocations in Suncus murinus. C.-banding of mitotic metaphase reveals that constitutive heterochromatin is centromeric in all the autosomes. In the sex-chromosomes, both centromeric and interstitial C-bands are observed.

Orientation of interphase chromosomes as detected by Giemsa C-bands.

The orientation of Giemsa C-bands has been studied in mitotic and interphase cells of Allium cepa. A sativum and of Aloe vera. The C-bands in these three species are located at the telomeres, secondary constriction region of the nucleolar chromosomes and the centromeric regions, respectively. Observations in A. cepa and Aloe indicate clearly that the interphase chromosomes are non-random in their orientation and possibly maintain their telophase configuration through the attachment of telomeres and perhaps of kinetochores with the nuclear membrane. Electron micrographs of onion cells also reveal that certain heterochromatic segments are associated with the nuclear membrane.--The nucleolar interstitial C-bands in A. sativum remain free in the nucleoplasm and may come close to each other due to heterochromatic attraction. Such a heterochromatic attraction is also evident between telomeric regions and between centromeres. However, a two by two attachment could not be noticed. A diagrammatic representation of the orientation of interphase chromosomes has been presented.

Chromosomenverh�ltnisse, konstitutives Heterochromatin und Geschlechtsbestimmung bei einigen Arten der GattungChrysomya (Calliphoridae, Diptera)

Compared with the strongly monogenic blowfliesChrysomya albiceps andC. rufifacies investigated previously, the closely related speciesC. chloropyga, C. putoria andC. varipes turned out to be amphogenic, i.e. each female of these species produces both sexes in nearly equal frequencies.C. chloropyga, C. putoria andC. varipes possess similar karyotypes consisting of five pairs of long identifiable autosomes and one pair of smaller sex chromosomes, which are homomorphic (XX) in the female and heteromorphic (XY) in the male. In all species the Y is shorter than the X. Among the cytologically known amphogenicChrysomya speciesC. varipes has the smallest heterochromosomes. Male meiosis inC. chloropyga, C. putoria andC. varipes is achiasmatic. During mitosis the autosomes show a high degree of somatic pairing but heterochromosomes, which form a heteropyknotic mass in the interphase nuclei, usually separate in the course of early mitotic prophase. A comparative study of C-banding patterns in mitotic and meiotic chromosomes ofC. chloropyga, C. putoria, C. varipes andC. rufifacies revealed that constitutive heterochromatin is present in almost all chromosomes. In the five pairs of large chromosomes it is confined to short regions adjacent to the kinetochores. An interstitial C-band has been observed only in the shorter arm of autosome no. 3 inC. putoria. With the exception of the tiny Y chromosome ofC. varipes, which seems to be completely euchromatic, all the other sex chromosomes of the amphogenicChrysomya species as well as the small chromosome no. 6 ofC. rufifacies possess longer or shorter C-segments. The karyotype ofC. varipes resembles closely that of the monogenic speciesC. albiceps andC. rufifacies thus indicating that the monogenic species could have evolved from an ancestral species closely related toC. varipes. The occurrence of two exceptional XO females and one exceptional XXY male among normal XX and XY animals in a wild stock ofC. chloropyga demonstrates that the Y chromosome of C. chloropyga and most probably of all amphogenicChrysomya species bears an epistatic male determining factor.