Showing papers on "Chromosome published in 1970"

Localization of 5S RNA Genes on Drosophila Chromosomes by RNA-DNA Hybridization

Abstract: [ 3H ] RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [ 3H ] uridine. Purified tritiated 5 S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5 S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [ 3H ] RNA and DNA was confined to the 56E-F segment.

Definitive Evidence for the Short Arm of the Y Chromosome associating with the X Chromosome during Meiosis in the Human Male

Abstract: MEIOTIC studies on the human male during the past thirty years, notably those of Koller1 and Ford and Hamerton2, have shown that the X and Y chromosomes associate at meiotic prophase. Whether the chromosomes form a true chiasma or not has never been demonstrated convincingly. Because the position of the centromeres of the chromosomes cannot be identified with certainty in meiotic preparations, there has been much speculation as to whether it is the long or the short arms of the Y chromosome which associate with the X. Thus, Sasaki and Makino3 suggested that the X–Y chromosome association involved the short arms of the Y, and Hulten et al.4 suggested the long arms of the Y. The best cytological evidence has come from McIlree et al.5 on a male with a dicentric Y chromosome involving a presumptive deletion of the short arms. At diakinesis the dicentric Y chromosome did not associate with the X, and Jacobs therefore suggested that in normal circumstances the Y chromosome might have associated with the X by its short arms6. From phenotype–karyotype correlations, Ferguson-Smith7,8 deduced that part of the long arms of the Y chromosome was homologous with part of the short arms of the X, and that this region was involved in the X–Y association. From the appearance of the X–Y association at diakinesis in testicular biopsies from a population of normal males, we have tentatively concluded that the short arms of the Y chromosome are involved in associating with the X chromosome.

Chromosome constitution and its bearing on the chromosomal radiosensitivity in man

Abstract: Blood samples obtained from patients with various types of inborn chromosome abnormalities were exposed to γ-rays and the relationship between the chromosome constitution and chromosomal radiosensitivity of lymphocytes was studied by analysing types and frequencies of radiation-induced chromosome aberrations. The results showed that the chromosomal radiosensitivity was consistently higher in the cells which were trisomic for the whole or a part of a chromosome than in the cells with normal karyotype, but it was not significantly influenced by the monosomic conditions, reciprocal translocation and inversion. Age of the subjects also affected the chromosomal radiosensitivity, which was elevated in the neonates. The analysis of chromosome aberrations showed that the high frequency of radiation-induced chromosome aberrations was due to the increased production of exchange aberrations and that the level of deletions was not affected either by factors of the chromosome constitution or of the age of the subject. A hypothesis to explain the increased chromosomal radiosensitivity of the trisomic cells was given in line with the effects of altered enzyme activity on the production of exchange aberrations. The parallelism between the increased chromosomal radiosensitivity in the trisomic cells and the susceptibility of the affected persons to neoplasia allowed us to recognize that the trisomic cells are particularly cancer-prone and that the illegitimate repair of chromosome damage, which is intrinsic to the trisomic cells, may play an important role in the development of cancer.

Unusual sex chromosome inheritance in mammals.

Abstract: The male has proven to be the heterogametic sex in all mammals studied so far. As is well known, the males usually have the sex chromosomes XY and the females XX. In recent years, however, many exceptions from this general pattern have been discovered. With our present knowledge, the different sex chromosome mechanisms in mammals may be divided into five main groups, and the first of them into subgroups, as follows: (i) Species with XX/XY sex chromosomes: (a) X of original size (see below), Y small; (b) X large, Y small; (c) X large, Y large: (i) end-to-end association of X and Y at male meiosis, (ii) chiasma between X and Y at male meiosis. (ii) Species with XX/XY1Y2 sex chromosomes. (iii) Species with X1X1X2X2/X1X2Y sex chromosomes. (iv) Species with complicated or unknown mechanisms for sex determination. (v) Species with mosaicism of the sex chromosomes, but apparently with an XX/XY mechanism for sex determination. The present contribution will mainly deal with unusual sex chromosome inheritance, that is the groups (ii), (iii) and (iv) above, but the other two groups will also be briefly discussed and examples will be given. Recently Raicu, Kirillova & Hamar (1969) described a new sex chromosome mechanism ( X1X1X2X2/X1X2Y1Y2) in the vole Microtus arvalis , but this observation was not confirmed by Schmid (1969), who found an ordinary XX/XY mechanism with both X and Y readily identifiable and of ‘normal’ size, the X comprising 5.6% of ( n A + X) and Y being the smallest chromosome of the complement. Late DNA replication was demonstrated in the allocyclic X and in the Y. Also Wolf (1969) found normal sex chromosomes in this species with no multivalents at male meiosis.

Chromosomal Distribution of Rapidly Reannealing DNA in Drosophila melanogaster

Abstract: Cytological hybridization has been used to localize fractions of rapidly reannealing DNA in salivary chromosomes of Drosophila melanogaster. Complementary RNA of high specific activity was transcribed from hydroxyapatite-fractionated rapidly reannealing sequences and from selected buoyant-density fractions of total DNA. It was then hybridized to chromosome squashes after denaturation of DNA in NaOH. Highly „repeated” DNA sequences were detected over much of the chromosome, but were concentrated in chromocentric heterochromatin. A family of sequences with a low percentage of guanosine plus cytidine was highly concentrated in a particular region within the chromo-center. One „euchromatic” region near the tip of chromosome arm 3L also exhibited a concentration of repeated sequences.

Chromosome studies on bone marrow from a male control population.

Abstract: Summary Chromosome analyses of bone marrow cells prepared by the direct method were carried out on 32 male patients, who had no primary haematological disease. One patient was found to have a pericentric inversion of the Y chromosome, which was also present in a skin fibroblast culture and in a lymphocyte culture. Three cases were found to have a high percentage of bone marrow cells with a 45,X chromosome constitution and one case had a 45, X?Y - or G- cell line. The high degree of aneuploidy was not found on examination of cells from leucocyte cultures. This observation is discussed in relation with other similar findings in patients with haematological diseases. The remaining 27 patients had a normal male karyo-type and showed only small deviations from the modal chromosome number. The percentage of bone marrow cells with either chromatid aberrations or stable chromosome abnormalities was not significantly different from previous observations on lymphocyte cultures. However, the proportion of cells with unstable chromosome abnormalities was found to be substantially reduced in comparison with results from cultured lymphocytes examined in their first in vitro division.

Cytochemical differentiation along human chromosomes.

Abstract: THE binding of fluorescent substances to well defined chromosomal regions has been demonstrated in plant and animal materials by Caspersson and his collaborators, and this taken as evidence for chemical differentiation along the chromosomes1,2. Quinacrine mustard (QM), an alkylating fluorochrome, binds very specifically to the heterochromatic areas or regions of the M chromosome of Vicia faba1,2. Alkylating agents are thought to interact with G·C-rich areas in DNA by alkylation of guanine3,4, and it was suggested that binding of such agents to chromosomal regions might indicate G·C-rich areas in them1,2. The specificity and reproducibility of these techniques in Vicia prompted me to explore their use with human chromosomes, possibly to identify individual chromosomes.

Cytological evidence on the origin of sweet potato.

Abstract: The results of intensive meiotic studies, particularly of the karyology and chromosomal homology at the pachytene stage, in the sweet potato (Ipomoea batatas L.), which is a hexaploid (2 n = 90), have thrown considerable light on its origin and genome relationships. Using suitable criteria, such as relative length of chromosomes, centromere position, chromomere pattern, absence of light staining segments in one of the arms, presence of telochromomere etc., 40 of the 45 haploid chromosome complement at pachytene were identified and assigned to 19 chromosomal types. Among these types, eight were present singly; in six of the types, chromosomes were present in duplicate, and in two types, in triplicate. The occurrence of higher multivalent chromosomal associations such as hexavalents and pentavalents, in addition to the quadrivalents already reported, was recorded for the first time at the pachytene and metaphase I stages. The hexavalents at pachytene were resolved into three distinct types based on the morphology of the participating chromosomes. A maximum number of nine quadrivalents at the metaphase I stage and four in the incompletely analyzed pachytene nuclei were recorded. The constituent chromosomes of three of the quadrivalents at pachytene stage were identified. From these observations, it is suggested that (i) the three parental genomes are partly homologous (ii) two of the genomes show closer homology to one another than to the third and (iii) the three genomes differ with respect to one or more of the eight chromosomal types occurring singly. The available information rules out an autopolyploid origin for sweet potato and suggests that the parental genomes are from closely related taxa. The advantages are emphasized of pursuing similar studies in other American Ipomoea species to unravel their relationship with the sweet potato. Among other meiotic irregularities, a translocated chromosome and a chromosome carrying inversion were detected at the pachytene stage and the possible role they may play in varietal differentiation is discussed.

Whole-mount electron microscopy of the centromere region of metacentric and telocentric mammalian chromosomes.

Abstract: Whole-mount electron microscopy of metaphase mouse L-cells showed that in many cases the region of the centromere was located at one extreme end of the chromosome with no evidence for short arms of any significant size. In such telocentric chromosomes there was only a single area of chromatid association. By contrast, the region of the centromere in mouse metacentric chromosomes was much longer. When well dispersed, it was seen to consist of two distinct areas of chromatid association, each of which was comparable in length to that of the telocentric chromosomes. In the region between these two areas there was a decrease in the density of the chromatin fibers. A similar quadripartite morphology was seen in human, Chinese hamster, and sheep metacentric chromosomes. These findings are most simply interpreted by the proposal that the quadripartite centromere of the metacentric chromosomes has resulted from the fusion of two telocentric chromosomes with bipartite centromeres.

A Genetic Map of Non-Mendelian Genes in Chlamydomonas

Abstract: A group of eight non-Mendelian genes have been shown by recombination analysis to be linked into a linear structure or chromosome. Similar genetic maps of gene order and relative distances between genes have been constructed by two methods, one based on additivity of recombination frequencies, the other on frequency of reciprocal recombination with a postulated attachment point. The data indicate that the progeny are diploid for this linkage group, and that the strands are distributed in a precisely oriented manner at mitosis. Evidence is discussed in support of the view that this linkage group is located in chloroplast DNA.

Chromosome weights and measures in the Triticinae.

Abstract: IT is widely accepted that the modern cultivated wheats such as Triticum aestivum (AABBDD) and Triticum durum (AABB) are, respectively, allohexaploids and allo-tetraploids derived from hybrids between diploid species of the Triticinae viz. T. monococcum (AA), Aegilops squarrosa (DD) and Aegilops speltoides (BB) (Riley, Unrau and Chapman, 1958; Jenkins, 1966). A question which arises is to what extent, if any, the chromosomes of the ancestral diploid species have changed subsequent to the hybridisation and polyploidy which gave rise to these modern allopolyploids. To answer this question three types of comparisons between the chromosomes of the diploids and polyploids can usefully be made. They are comparisons with respect to the size of chromosomes, their total dry mass and the DNA component of their mass. Using chromosome length as a measure of chromosome size, Bhaskaran and Swaminathan (1960) show significant variation between the chromosomes of the diploids, the tetraploids and the hexaploids. Pal and Swaminathan (1960) use this evidence together with information on DNA content obtained by Bhaskaran and Swaminathan (bc. cit.) to support an hypothesis which claims that a diminution in chromosome size and DNA content has occurred during the evolution of the wheats. The DNA results obtained by Bhaskaran and Swaminathan are, however, questionable (Rees and Walters, 1965; see also Upadya and Swaminathan, 1963) so that the main evidence for a chromosome diminution in the allopolyploids rests on comparisons between chromosome size based on measurements of length. The validity of length alone as a measure of chromosome size is also questionable. It does not take into account variation attributable to differences in chromosome coiling. Estimates of size based on chromosome volume are, in this respect, preferable and have been used in this present work. Measurements of the dry mass of chromosomes provide further and more precise information about structural changes, such as large scale diminution or, for that matter, accretion of chromosome material that may have taken place during this evolutionary process. In conjunction with DNA measurements the estimates of dry mass of the chromosomes also make it possible to ascertain whether the components of the chromosome mass, the DNA and non-DNA material, vary independently of one another between the diploids and their polyploid descendants. In other words, they permit comparison of a qualitative as well as a quantitative kind between the modern and ancestral forms. Chromosome measurements were made in several species of the Triticinae other than those already mentioned. Together they provide useful information upon the relations and interrelations between various aspects of chromosome organisation within the family.

Chromosome Loss compared with Chromosome Size, Age and Sex of Subjects

Abstract: STUDIES of human chromosomes1–7 have demonstrated that ageing increases hypodiploidy. Sex differences were said to account for different rates of increase in hypodiploidy as well as the preferential loss of an X chromosome in females and a Y chromosome in males2,4–6.

The discriminating fluorescence patterns of the chromosomes of Drosophila melanogaster.

Abstract: Mitotic and salivary gland chromosomes of D. melanogaster show striking fluorescent patterns when stained with Quinacrine. In the salivary gland chromosomes there are up to five strongly fluorescing bands located on the fourth chromosome and at the proximal end of the X chromosome.—In mitotic cells the Y chromosome shows four fluorescent segments and other fluorescent regions are found proximally on the third pair and on the X chromosome. It is, therefore, possible to distinguish male and female interphase cells by their patterns of fluorescence.—A comparison between the position of heterochromatic, late replicating and fluorescing segments in the mitotic chromosomes, shows differences which demonstrate, for the first time, the chemical, morphological and genetical diversity of these three types of segments.

Natural variation in nuclear characters of meristems in Vicia faba.

Abstract: The natural variation in chromosome size in root-tip and shoot apex meristems of Vicia faba has been studied. Chromosomes in main root-tips of one week old plants are 2–3 times larger than those in small lateral root-tips of 3 week old plants. While the nuclear DNA content remains constant, the nuclear RNA and nuclear histone contents show a positive linear correlation with chromosome volume. The DNA: histone ratio varies and is lowest in cells with large chromosomes. Nuclear volume and chromosome volume are not linearly related and changes in nuclear density therefore seem likely. A positive linear relationship between chromosome volume and mitotic index in colchicined squashes is demonstrated. The results strongly suggest that variation in chromosome size indicates a corresponding change in the rate of cell metabolism and may well reflect change in genetic activity.

Homoeologous meiotic chromosome pairing in Triticum aestivum in which chromosome 5B is replaced by an alien homoeologue.

Abstract: In the hexaploid bread wheat (Triticum aestivum 2n = 6x = 42) meiotic pairing is confined to fully homologous chromosome partners and inheritance is disomic. This arises from the activity of a single locus (Ph, pairing homoeologous) distally located on the long arm of chromosome 5B1,2. In the absence of chromosome 5B, pairing and recombination take place between homoeologous chromosomes, which are genetically related members of the three component genomes, as well as between homologues3. Knowledge of the 5B system is of fundamental and practical significance. It throws light on the process of chromosome pairing during meiosis4, and assists in the interpretation of the cytogenetic behaviour of polyploid wheat, and indeed of all allopolyploids. Moreover, interference with its activity has been exploited to cause abnormal recombination between homoeologues in order to introduce into wheat chromosomes useful genes from chromosomes of related species5. Consequently to extend the understanding of the system, as well as to facilitate its use in breeding work, attempts are continually being made to isolate new wheat genotypes displaying homoeologous pairing.

The Christchurch chromosome (Gp-). Mongolism, erythroleukemia and an inherited Gp- chromosome (Christchurch).

Abstract: An 18-month-old male infant with mongolism and erythremic myelosis had two cell lines in his bone marrow and peripheral blood: one cell line, with 47 chromosomes, had 2 Gp— chromosomes, and the other, with 51 chromosomes, had 3 Gp—chromosomes. He died of acute myeloblastic leukemia at 21 months of age. The Gp— chromosome was present in four generations of his family; his mother, his maternal grandmother and his maternal maternal great-grandmother were carriers and phenotypically normal. The Gp— chromosome has not previously been reported in a patient with erythremic myelosis, an uncommon disease in children. Review of all reported propositi and members of their families with the Gp— chromosome shows no consistent phenotypic effect of this deletion. However, among 37 progeny of 18 carriers of the Gp— chromosome, five have had mongolism with 47 chromosomes. The Gp— chromosome itself appears to segregate normally among the progeny of carriers.

The mechanism of somatic association in common wheat, triticum aestivum l. ii. differential affinity for colchicine of spindle microtubules of plants having different doses of the somatic-association suppressor

Abstract: HE homologous chromosomes of common wheat, Triticum crestiuum L., are Tassociated in somatic cells (FELDMAN, MELLO-SAMPAYO and SEARS 1966). This somatic association is regulated by a gene system located on the chromosomes of homoeologous group 5, i.e., chromosomes 5A, 5B, and 5D, (FELDMAN 1966, 1968). The long arm of chromosome 5B (5BL) carries a gene which SUPpresses somatic association and thus tends to cause random distribution of homologues in the somatic nucleus. On the other hand, the short arm of chromosome 5B (5BS) and the long and short arms of chromosomes 5A and 5D carry genes which promote somatic association. The effect of the somatic-association promoters is opposite to that of the somatic-association suppressor. Thus in common wheat there is a balance between the suppressor and the several promoters which determines the degree of somatic association that occurs. Studies on the effect of the somatic-association genes in aneuploid wheat plants having different doses of chromosomes 5B, 5D, and 5A have shown that this balance can be shifted in either direction (FELDMAN 1966, 1968) by increasing the dose of suppressor or promoter or by deleting the suppressor or one of the promoters, with resultant reduction or enhancement of the degree of association between homologues in somatic cells. The feasibility of such shifts in balance provides an excellent means for the study of the control and mechanism of somatic associa tion. In a previous paper, AVIVI, FELDMAN and BUSHUK (1969) reported that colchicine, when applied at interphase, suppressed the association of homologous chromosomes in root-tip cells of common wheat. Since any disruption of a cell function caused by colchicine indicates that this function is dependent upon the existence of microtubular proteins ( WEISENBERG, BORISY and TAYLOR 1968), we suggested that a microtubular protein plays a decisive role in the association of homologous chromosomes in somatic cells. Colchicine supposedly suppressed somatic association by disrupting the organization of these microtubules.

Rearrangements between germ-line Limited and somatic chromosomes in Smittia parthenogenetica (Chironomidae, Diptera)

Abstract: Among more than 700 chromosome rearrangements induced by X-rays in oocytes of newly hatched females of Smittia parthenogenetica two cases of insertion of heterochromatin into an S chromosome have been obtained. As the S chromosomes do not contain such heterochromatic sections, the insertions must be derived from K chromosomes. Whether all K chromosomes are completely heterochromatic or whether all or some contain euchromatic sections remains open, but for the two latter possibilities no proof has been obtained. Euchromatic insertions or translocations with a banding pattern non-homologous with S chromosome sections have not been observed with certainty. Homologous duplications could all be interpreted as being derived from S chromosomes. From the K chromosome cycle it can be inferred that the K complement consists of more or less identical elements and that genetic isolation has led to their heterochromatinization.

CHROMOSOME RELATIONSHIPS BETWEEN THE CULTIVATED OAT AVENA SATIVA (6x) AND A. VENTRICOSA (2x)

Abstract: Chromosome pairing in the F1 hybrid between the cultivated oat Avena sativa and a diploid species A. ventricosa, and in the derived amphiploid, shows that the diploid species is related to one of t...