Showing papers on "Heterochromatin published in 1973"

Chromosome homology and heterochromatin in goat, sheep and ox studied by banding techniques

Abstract: Peripheral blood lymphocyte metaphase chromosomes of three Bovoidean species have been studied using Quinacrine fluorescence and Giemsa banding techniques to give Q-, G-, and C-banding patterns. Q- and G-banding characteristics, coupled with chromosome length, enabled all of the chromosomes in each of the chromosome complements to be clearly distinguished, although some difficulties were encountered with the very smallest chromosomes. A comparison of G-banding patterns between the species revealed a remarkable degree of homology of banding patterns. Each of the 23 different acrocentric autosomes of the domestic sheep (2n=54) was represented by an identical chromosome in the goat (2n=60) and the arms of the 3 pairs of sheep metacentric autosomes were identical matches with the remaining 6 goat acrocentrics. A similar interspecies homology was evident for all but two of the autosomes in the ox (2n=60). This homology between sheep metacentric and goat acrocentric elements confirms a previously suggested Robertsonian variation. The close homology in G-banding patterns between these related species indicates that the banding patterns are evolutionarily conservative and may be a useful guide in assessing interspecific relationships. —The centromeric heterochromatin in the autosomes of the three species was found to show little or no Q-or G-staining, in contrast to the sex chromosomes. This lack of centromeric staining with the G-technique (ASG) contrasts markedly with results obtained with other mammalian species. However, with the C-banding technique these regions show a normal intense Giemsa stain and the C-bands in the sex chromosomes are inconspicuous. The amount of centromeric heterochromatin in the sheep metacentric chromosomes is considerable less than in the acrocentric autosomes or in a newly derived metacentric element discovered in a goat. It is suggested that the pale G-staining of the centromeric heterochromatin in these species might be related to the presence of G-Crich satellite DNA.

Heterochromatin recognition and analysis of chromosome variation in Scilla sibirica

Abstract: The heteroohromatin of Scilla sibirica, consists of two distinct types: 1) showing enhanced Quinacrine fluorescence and located near the centromere of all the chromosomes of the complement, and 2) with reduced Quinacrine fluorescence and located in various positions along the chromosomes. After a denaturation-reannealing treatment both heterochromatin types are stained by Giemsa, and by acetic-orcein. Acetic-orcein, however, tends to stain preferentially the reduced fluorescence segments. An analysis of chromosome variation in a population of twenty plants, reveals that all the plants are unique in their heterochromatic segment endowment. All the chromosomes are polymorphic but there is a certain constancy for band patterns in individual chromosome types, and for the number of bands per chromosome complement.

The chromosomal location of human satellite DNA 3.

Abstract: In situ hybridisation of radioactive complementary RNA has been used to localise the chromosomal distribution of human satellite DNA III. This DNA is found to be concentrated in paracentromeric heterochromatin mainly on chromosome 9 and in minor concentrations on chromosomes chiefly of the D and G groups.

Centromeric heterochromatin polymorphism in the house mouse. Evidence from inbred strains and natural populations.

Abstract: Polymorphism of Giemsa-specific centromeric heterochromatin (C.H.) has been described in the laboratory and wild mice. All examined wild mice and inbred mouse strains display some chromosomes with considerably reduced or enlarged C.H. regions. The quantity of C.H. could be an inherent property of a chromosome as inferred from (a) the finding of the identical C.H. pattern within inbred strains, (b) the finding that two genetically related inbred strains, C3H and CBA, separated from each other for more than 150 generations, possess the same two chromosome pairs with tiny C.H. marker regions. These chromosomes were identified as No. 1 (l.g. XIII) and No. 14 (l.g.III) by means of T(14;15)6Ca translocation, and C- and G-band analysis. The neutrality of C.H. polymorphism in murine genome is inferred from the “heterozygosity” for the C.H. variants found in all studied wild mice. The possible relationship of C.H. polymorphism to the centromere interference phenomenon is hypothesized.

Nondisjunction: localization of the controlling site in the maize B chromosome.

Abstract: Nondisjunction of the B chromosome in maize has been considered to be controlled by heterochromatin in its long arm. Experiments reported here indicate that the control site actually lies in a short, relatively euchromatic segment distal to the major heterochromatin of the long arm.

A note on the maternal effect mutants daughterless and abnormal oocyte in Drosophila melanogaster.

Abstract: Two deficiencies for, and a dominant enhancer of, the second chromosome maternal effect mutant, "daughterless" (da), were induced with X-irradiation. Their properties were studied with respect to both da and the linked maternal effect mutant, "abnormal oocyte" (abo), with the following conclusions. (1) The most probable map positions of da and abo are: J—½—da—2½—abo, where J is a dominant marker located at 41 on the standard map. (2) The da locus is in bands 31CD-F on the polytene chromosome map; abo is to the right of 32A. (3) Because homozygous da individuals survive while individuals carrying da and a deficiency for da are lethal, it is concluded that da is hypomorphic. (4) From a weak da-like maternal effect in heterozygous da females induced by an "Enhancer of da," we have confirmed a previous report that (a) the amount of sex chromosome heterochromatin contributed by the father can influence the severity of the da maternal effect, and (b) the sex chromosome heterochromatin which influences the da effect is different from that which influences the abo effect. (5) The possibility that da and abo are in a special region of chromosome 2 concerned with the regulation of sex chromosome heterochromatin is strengthened by the observation that the Enhancer of da appears to rescue abnormal eggs produced by homozygous abo mothers. (6) The Enhancer of da is a translocation between chromosomes 2 and 3 with the second chromosome breakpoint in the basal heterochromatin; because the enhancing effect maps in this region of chromosome 2, it is possible that autosomal, as well as sex chromosomal, heterochromatin interacts with da and abo.

The heterochromatic B chromosome of maize: the segments affecting recombination

Abstract: The B chromosome of maize is known to increase recombination in specific regions of the genome. In an attempt to determine the portion of the B responsible for crossover enhancement, translocations between the B and A chromosomes were used to dissect the B into four distinct segments. The effects of the segments on crossing over were studied in a sensitive region composed of chromatin from chromosomes 3 and 9. The relatively euchromatic chromomeres terminating the B lacked enhancement activity, but the remaining segments, all of which possess large amounts of heterochromatin, were capable of elevating recombination. There was no localization of activity to a specific heterochromatic region, however.

Aspect cytologique et localisation intranucléaire de l'hétérochromatine constitutive des chromosomes C9 chez l'homme

Abstract: Using a specific technique which stains the secondary constriction of number 9 chromosomes in man, we observed that this segment frequently appears to be composed of multiple small units packed together in metaphase as well as in interphase. During prophase of the first meiotic division in man, this segment looks like a diffuse structure, suggesting division and multiplication of these units. On the other hand, the C9 bodies observed in interphase with this cytological procedure are frequently associated with the nucleolus. This heterochromatin is less compact than previously shown and may represent repetitive DNA with a specific role.

Observations on centromeric heterochromatin and satellite DNA in salamanders of the genus Plethodon.

Abstract: DNA from Plethodon cinereus cinereus separates into two fractions on centrifugation to equilibrium in neutral CsCl The smaller of these fractions has been described as a high-density satellite It represents about 2% of nuclear DNA from this species, and it has a density of 1728 g/cm3 It is cytologically localized near the centromeres of all 14 chromosomes of the haploid set In P c cinereus the heavy satellite DNA constitutes about 1/4 of the DNA in centromeric heterochromatin The nature of the rest of the DNA in centromeric heterochromatin is unknown The number of heavy satellite sequences clustered around the centromeres in a chromosome from P c cinereus is roughly proportional to the size of the chromosome, as determined by in situ hybridization with satellite-complementary RNA, and autoradiography Likewise the amount of contromeric heterochromatin, as identified by its differential stainability with Giemsa, shows a clear relationship to chromosome size — The heavy satellite sequences identified in DNA from P c cinereus are also present in smaller amounts in other closely related forms of Plethodon Plethodon cinereus polycentratus and P richmondi have approximately half as many of these sequences per haploid genome as P c cinereus P hoffmani and P nettingi shenandoah have about 1/3 as many of these sequences as P c cinereus P c cinereus, P c polycentratus, and P richmondii all have detectable heavy satellites with densities of 1728 g/cm3 Among these forms, satellite size as determined by optical density measurements, and number of satellite sequences as determined from hybridization studies, vary co-ordinately P c cinereus heavy satellite sequences are not detectable in P nettingi, P n hubrichti, or P dorsalis The latter species has a heavy satellite with a density of 1718 g/cm3, representing about 8% of the genomic DNA, and two light satellites whose properties have not been investigated The heavy satellite of P dorsalis is cytologically localized in the centromeric heterochromatin of this species — These observations are discussed in relation to the function and evolution of highly repetitive DNA sequences in the centromeric heterochromatin of salamanders and other organisms

Variation of constitutive heterochromatin in the sex chromosomes of the rodent Bandicota bengalensis bengalensis (Gray).

Abstract: Bandicota bengalensis bengalensis (Gray) trapped from different localities of India and Nepal exhibited a marked variation in the size and morphology of sex chromosomes. Three types of X's were found; A) simple acrocentric, B) composite subtelocentric and C) composite submetacentric X with their relative sizes 5.9%, 7.5% and 9.6% of the genome respectively. The autosomes remained unaltered. It was shown that this variation in the size of sex chromosomes was caused by deletion of constitutive heterochromatin. The Y chromosome was also found to be variable. Usually a large X was combined with a large Y. The preponderance of homozygotes for each type of X chromosome in populations, suggested the probable role of sex chromosomes heterochromatin in speciation.

Clonal variants of constitutive heterochromatin of human fibroblasts after recovery from mitomycin treatment.

Abstract: Presumptive clones of human skin fibroblast-like cells surviving mitomycin C treatments show a variety of intra- and interchromosomal rearrangements limited to the constitutive heterochromatic regions. Starting with a wild-type line polymorphic for chromosome no. 1 heterochromatin, we have observed clones with complete symmetry and varying degrees of asymmetry of the no. 1 heterochromatin, translocations of “excess” chromosome 1 heterochromatin to one no. 9 member, interstitial translocations to sites normally devoid of heterochromatin, and duplication of the Y chromosome long arm heterochromatin. In the case of the chromosome no. 1 pair, the extent of heterochromatin variation was quantitated to test the hypothesis that discrete classes of variants occur. There appear to be two types of variants: Those showing reciprocal changes between homologues (2 examples) and those showing a change in the amount of heterochromatin of a single homologue (5 examples). The latter group showed an approximately linear series of variants. Unequal cross-over following repair after damage from the alkylating agent is considered the most likely explanation for the observed changes, given the repetitive nature of DNA at these heterochromatic sites.

Heterochromatin late Replication and Secondary Constrictions in the Chromosome Complement of Leptodactylus Ocellatus

Abstract: SUMMARYThe distribution of secondary constrictions, late replication and c-heterochromatin (as demonstrated by the DNA d-r method) was analysed in the chromosome complement of L. ocellatus. The finding of late and non-late replicating c-heterochromatin allow to surmise that c-heterochromatin is probably an heterogeneous substance formed by different families of repetitive DNA. The coincidence of c-heterochromatin with late replication and secondary constrictions may represent the location of the nucleolar-associated heterochromatin.Several regions of the complement showed the combination of a positive (late replication) with a negative property (lack of differential stain with the DNA d-r method). It is known that f-heterochromatin does not react with the DNA d-r method. Therefore, it is discussed whether the foregoing areas can be considered f-heterochromatin.

Equations defining the position of ribosomal cistrons in the eukaryotic chromosome.

Abstract: THE organization of the eukaryotic chromosome at both structural and molecular levels has been much studied. The distribution of heterochromatin in the form of chromomere gradients, originating on both sides of the kinetochore and the non-random distribution of specific DNA segments along the chromosome, strongly suggested precise genetic interrelations among its regions1 which led to the concept of chromosome field2. The field is considered to be the expression of a hierarchic system within the eukaryotic chromosome, in which kinetochores, telomeres, nucleolar organizers, knobs and other DNA segments interact with one another in decreasing order of importance, the results of their interactions deciding the genetic pattern of the chromosome3.

DNA synthesis in rye chromosomes.

Abstract: Following the uptake of tritiated thymidine during the latter part of the synthesis (S) phase of mitosis the distribution of label at metaphase varies between chromosomes and between segments within chromosomes. Per unit volume B chromosomes are more densely labelled than the normal, A chromosomes of the rye complement. Within A chromosomes the terminal segments and centromere regions are the most heavily labelled. Analyses are presented which distinguish between the different causes of heavy labelling. In terminal segments of the long arms late completion of DNA synthesis in heterochromatin contributes to the heavy labelling. In contrast the disproportionately heavy labelling in B's is attributable to a higher DNA density in B, as compared with A chromosomes, at metaphase. It is probable that the heavy labelling around the centromeres of rye chromosomes is, also, a reflection of a higher DNA density at metaphase. Our evidence indicates it is not due to a late completion of DNA synthesis. B chromosomes have no influence upon the pattern of labelling in A chromosomes. It is possible that they reduce the rate of DNA synthesis during S.

Chromosome breakage in Drosophila melanogaster induced by a monofunctional alkylating agent (EMS).

Abstract: Ethyl methanesulfonate (EMS)-induced mutations involving the yellow locus of Drosophila melanogaster were studied, both when the dominant alleles for yellow ( y + ) and closely linked achaete ( ac + ) were adjacent to euchromatin in their normal position on the left end of the X chromosome and when adjacent to constitutive heterochromatin on the Y chromosome. A yellow mutation was considered intragenic if the adjacent achaete locus was not affected. The intragenic mutation frequency did not change with the position of the yellow locus in the genome; however, the total mutation frequency was three-fold higher when the yellow locus was positioned adjacent to consititutive heterochromatin. Results show that an additional class of mutations resulting from chromosome breakage accounts for the increased mutational frequency when the yellow locus is adjacent to heterochromatin.

Nonrandom arrangement of human chromatin: topography of disomic markers X, Y, and 1h+

Abstract: Numerical and structural variants (47,XXX; 92,XXXX; 47,XYY; 92,XXYY; 92,lh+lh+) were used to determine the topography of chromatins of different molecular composition in cultivated fibroblast-like cel

The nature and inheritance of an elongated secondary constriction on chromosome 9 of man.

Abstract: An unusually long secondary constriction on chromosome 9 was shown by C-staining to involve duplication of heterochromatin in this region. The constriction stained darkly following the C-staining procedure but was unstained following the G-staining procedure. The heterochromatic constriction generally completed DNA replication earlier than the remainder of chromosome 9. The abnormal chromosome was detected in 17 individuals belonging to three generations of a family. There were twice as many carriers as noncarriers. Similar excesses of carriers were noted in two other pedigrees reported in the literature. Disturbed segregation of this abnormal chromosome 9 is suggested and is consistent with the increased centromeric heterochromatin present. No linkage to chromosome 9 was demonstrated, but Rh-linkage was discounted.

Satellite DNA in the sheep and goat

Abstract: Sheep and goats possess closely similar satellite DNAs which seem to be concentrated in the heterochromatin and the nucleolus. In both species, the major and minor satellites have buoyant densities of 1.711 g·cm −3 and 1.718 g·cm −3 and represent 12% and 2.5%, respectively, of the total DNA. Major satellite concentration in the combined heterochromatin and nucleolar fraction was 19%, and in the pure nucleolar fraction it was 51%. Most hitherto reported satellite DNAs have varied markedly in density and concentration from species to species, even within the same genus. The close similarity of the sheep and goat satellite is discussed in the light of what is known about the evolutionary relationship between the sheep and the goat and in the light of various hypotheses concerning the possible functions of satellite DNA.

Loss of heteropycnosis of the constitutive heterochromatin in specifically activated cells of the thyroid gland of Microtus agrestis.

Abstract: In nuclei of the inactive thyroid gland of Microtus agrestis the constitutive heterochromatin is heteropycnotic and forms large chromocenters. After specific activation of the thyroid gland with thyroid stimulating hormone (TSH), or with the thyrostatic methylthiouracil (MTU), an enlargement of cells and nuclei, a high mitotic activity and a despiralization of the contitutive heterochromatin are observed. The facultative heterochromatin, on the contrary, remains condensed. The structure of the nuclei of the parathyroid gland is not altered by the treatment with TSH or MTU. The findings permit the assumption that constitutive heterochromatin has specific functions, e.g. as a nucleolus organizer, which are blocked in the heteropycnotic state and active in the isopycnotic state.

A method for the quantitative evaluation of eu- and heterochromatin in interphase nuclei using cytophotometry and pattern analysis.

Abstract: Summary The method described herein for the quantitative evaluation of the amount of eu- and heterochromatin in a single interphase cell nucleus is based upon the measurement of optical density in Feulgen-stained nuclei with a scanning cytophotometer (UMSP I). The digitalized values for each grid point are entered via punched paper tape into a computer and processed therein. The position and optical density level of the grid points serve as criteria for the recognition of heterochromatin. The computer calculates the total DNA content of all such points, as well as the proportion of this heterochromatin DNA with respect to the entire DNA content of the cell nucleus. The heterochromatin contents so obtained agree with values obtained from a densitometric determination from photographs of cell nuclei. Agreement with cytogenetic experiments is also observed. The applicability of the method is demonstrated for the heterochromatin content of a variety of rodent species.

Heterochromatin and Giemsa Banding of Metaphase Chromosomes in Trillium kamtschaticum Pallas

Abstract: RECENT development of the Giemsa staining method1–9, as well as the in situ hybridization technique1,10–13 or the quinacrine fluorescence technique14,15, greatly facilitates studies on chromosome structure, especially on the linear differentiation of the metaphase chromosome. At an early stage of the study the regions darkly stained by the Giemsa method were considered to be heterochromatin1,2. Supporting evidence was also obtained through studies in plants16,17. Confronted with findings of the G-banding5–9, however, generalization of this rule was questioned. We attempted to see whether the Giemsa positive regions are not necessarily the heterochromatin, using Trillium kamtschaticum as material in which the numbers and locations of large heterochromatin segments (faintly Feulgen-stained segments after cold treatment) have been well established18 in the large metaphase chromosomes.