Showing papers on "Chromosome published in 1977"

The cytogenetics of Neurospora.

Abstract: Publisher Summary This chapter concerns genetically significant aspects of Neurospora cytology, and the relation between genes and chromosomes, with special emphasis on chromosome rearrangements. In addition to reviewing the published literature, numerous results have been presented. Many of these are cytological, appearing under various headings. The chapter is also concerned with the morphology and identification of individual chromosomes. New genetic results concerning chromosome rearrangements and general characteristics of aberrations are given and a brief description of each known rearrangement has been provided. The chapter also deals briefly with other topics such as accessory, the genetic control of recombination, and the cytoplasmic genome. Neurospora possesses several favorable features compared to the more conventional organisms that are used in cytogenetic research, and these, in part, compensate for the small size of its chromosomes. All four products of individual meioses survive. Progeny can be obtained either as random meiotic products, as unordered tetrads, or as ordered tetrads whose linear spore arrangement reflects the events of meiosis. The spores show high viability and germination. The vegetative (somatic) part of the life cycle is haploid. Duplications are more readily identified as partial diploids against a haploid background than as partial triploids against a diploid background. Somatic variants can be obtained in pure culture. Any somatic cell can serve as a germ cell. For Aspergillus, only a few rearrangements have been recognized in other eukaryotic microorganisms, where usually they are more difficult to detect than in Neurospora, with its pigmented spores. Failure to recognize an existing rearrangement can lead to spurious conclusions regarding linkage, recombination, interference, preferential segregation, or the presence of synthetic lethal genes.

Double minute chromosomes and the homogeneously staining regions in chromosomes of a human neuroblastoma cell line

Abstract: Four human neuroblastoma cell lines were studied by chromosome banding techniques. All of the lines contained a marker chromosome with a long nonbanding homogeneously staining region (HSR). The HSR-containing chromosome differed in each line. One line contained two classes of cells: one with an HST marker chromosome and the other with double minute chromosomes. Each cell had one of these abnormalities; no cell had both. The presence of two additional chromosomal markers in all cells of this line indicates a common origin. These observations suggest that the double minute chromosomes are derived from the HSR.

The diminution of Heterochromatic chromosomal segments in Cyclops (Crustacea, Copepoda).

Abstract: The chromosomes of Cyclops divulsus, C. furcifer, and C. strenuus, like those of several other Copepods, undergo a striking diminution of chromatin early in embryogenesis. The process is restricted to the presumptive soma cells and occurs at the 5th cleavage in C. divulsus, at the 6th and 7th in C. furcifer, and at the 4th in C. strenus. The eliminated chromatin derives from the excision of heterochromatic chromosome segments (H-segments). Their chromosomal location is different in the three investigated species: Whereas in C. divulsus and C. furcifer the H-segments form large blocks-exclusively terminal in the former and terminal as well as kinetochoric in the latter-the germ line heterochromatin in C. strenuus is scattered all along the chromosomes. Extensive polymorphism exists with respect to the length of the terminal H-segments in C. furcifer, and with respect to the overall content of heterochromatin in the chromosomes of C. strenuus. In a local race of C. strenuus an extreme form of dimorphism has been found which is sex limited: females as a fule are heterozygous for an entire set of large (heterochromatin-rich), and a second set of small chromosomes in their germ line. Males are homozygous for the large set. In the first three cleavage divisions the H-polymorphism is solely expressed through differences of chromosome length. Following diminution the differences between homologous have disappeared. Feulgen cytophotometry demonstrates that in the three species the 1C DNA value for the germ line, as measured in sperm, is about twice that measured in somatic mitoses (germ line/soma C-values in picograms of DNA: C. strenuus 2.2/0.9, C. furcifer 2.9/1.44, C. divulsus 3.1/1.8). - The data imply that chromatin diminution is based on a mechanism which allows specific DNA segments, regardless of their location and size, to be cut out from the chromosomes without affecting the structural continuity of the remaining DNA. The mechanism may be analogous to that of prokaryotic DNA excision.

Ultraviolet light sensitivity and delayed DNA-chain maturation in Bloom's syndrome fibroblasts

Abstract: BLOOM'S syndrome (BS) is a rare, autosomal recessive condition of pre-natal and post-natal growth retardation, sun-induced telangiectatic erythema, impaired immunological function and predisposition to cancer1,2. BS cells show a high incidence of chromosome breakage and rearrangement often with abnormal nuclear morphology. Chromosome exchanges appear mainly to involve homologous chromosomes, while sister chromatid exchanges are abnormally frequent3. These features suggest a defect of DNA replication or repair. In particular, the high incidence of sister chromatid exchanges may be explained if free ends in the DNA, resulting from abnormalities of DNA synthesis and/or repair, act as initiation points for exchange4. We report here that BS fibroblasts are abnormally sensitive to ultraviolet irradiation in vitro and show a rate of DNA synthesis and DNA chain maturation lower than controls. They do not, however, have defective bypass of ultraviolet light-induced lesions during DNA replication as xeroderma pigmentosum (XP) variants5.

Variation in nuclear DNA in the genus Secale

Abstract: Estimates of the 4C DNA amount per nucleus in 16 taxa of the genus Secale made by Feulgen microdensitometry ranged from 28.85 picograms (pg) in S. silvestre PBI R52 to 34.58 pg in S. vavilovii UM 2D49, compared with 33.14 pg in S. cereale cv. “Petkus Spring” which was used as a standard. Giemsa C-banding patterns showed considerable interspecific and intraspecific variation and several instances of polymorphism for large telomeric C-bands. The proportion of telomeric heterochromatin in the genome ranged from about 6% in S. silvestre and S. africanum to about 12% in cultivated rye. A detailed comparison of nine taxa showed no overall relationship between 4C DNA amount and the proportion of telomeric heterochromatin in the genome. However, evidence is presented which strongly supports the notion that the major evolutionary change in chromosome structure in Secale has involved the addition of heterochromatin at, or close to, the telomeres. It is suggested that saltatory amplification events at telomeres were initially responsible for each large increase in DNA amount. Subsequently unequal crossing over between homologues may have played an important secondary role by extending the range of variation in the amount of heterochromatin at a given telomere, while crossing over between non-homologues may have provided a useful mechanism allowing an increase in the DNA amount at one telomere to be distributed between chromosomes.

Chromosomal location and evolution of isozyme structural genes in hexaploid wheat

Abstract: The genetic control of the production of multiple forms of lipoxygenase, endopeptidase, acid phosphatase, aminopeptidase, and alcohol dehydrogenase in hexaploid wheat has been studied using the zymogram technique. Aneuploid strains which encompass a range of from zero to four doses of each chromosome in the complement were analysed. The localisation of 22 structural genes to specific chromosome arms is reported. Extensive inter-genomic variation between homoeologous isozyme structural genes has been detected. The results of this study are consistent with the hypothesis that many of the duplicated structural genes of this species have diverged in structure and function subsequent to the origin of the polyploid wheats.

Frequency of satellite association of human chromosomes is correlated with amount of Ag-staining of the nucleolus organizer region.

Abstract: Methaphase chromosomes from karyotypically normal adult humans (three males, six females) and one male with a 13p - chromosome were stained by quinacrine and then by the Ag-AS silver staining method to reveal nucleolus organizer regions (NORs). Each person had a characteristic number of Ag-stained chromosomes per cell, always fewer than 10. Determination of the mean Ag-size of each chromosome showed that each of the 10 individuals had a unique distribution of Ag-stain. Within each individual, there was some variation from cell to cell in the number of acrocentric chromosomes that were Ag-stained; this was not random, and the same chromosomes (those that had at most a small amount of Ag-stain) tended to be unstained in every cell. Satellite associations were scored on the same cells. Chromosomes that had no Ag-stain were involved in satellite association less than 20% as often as those that had some Ag-stain. Chromosomes that had a small amount of Ag-stain were involved in association about 50% as often as those that had a large amount of stain. Regression analysis of the 50 (of a total of 100) acrocentric chromosomes which could be individually identified by quinacrine markers showed that the frequency with which a chromosome was involved in satellite association was strongly correlated with the amount of Ag-stained material in the NOR.

Chromosome Stability in CHO Cells

Abstract: The established cell line derived many years ago from Chinese hamster ovary (CHO cells) has been studied for the extent of chromosomal variation. Because this cell line is used extensively for genetic studies, the contribution of chromosome variability to genetic variability has also been examined. The quasidiploid CHO cells were found to have a banded karyotype somewhat altered from that of the Chinese hamster from which the line was derived. However, most of the genome could be accounted for among the rearranged marker chromosomes. In addition, the CHO line was found to have a relatively stable karyotype, the same basic karyotype being found in a majority of the uncloned cells, as well as in most cells of several but not all independent clones. Many, but not all, mutant cell lines derived from CHO also showed the same basic karyotype. Quasitetraploid cells, derived either spontaneously or by Sendai-virus-induced fusion, showed considerably more variation resulting in loss or gain of whole chromosomes, rearrangement of chromosomes, and appearance of new “marker” chromosomes.

Chromosomes 1 in 14 ovarian cancers. Heterochromatin variants and structural changes.

Abstract: Structurally rearranged chromosomes 1 were found in 9 out of 14 ovarian carcinomas and may also have been present in three others. In the remaining two, pericentric inversions involving the heterochromatic regions of chromosomes 1 were seen, and were also identified in one of the chromosomes 1 in the patient's normal cells (lymphocytes). Altogether, heterochromatin variants (variation in size and/or the presence of a pericentric inversion) were seen in the tumour cells of eight cases, and one or both types of variation were identified in the normal cells of six of these. The possibility of an association between the presence of chromosome 1 heterochromatin variants as a constitutional anomaly, a liability to ovarian (and perhaps other forms of) cancer and structural changes involving the chromosomes 1 in the tumour cells is considered.

Nucleolus organizers in Mus musculus subspecies and in the RAG mouse cell line.

Abstract: Silver staining has been used to detect active nucleolus organizer regions (NOR's). By this criterion six mouse chromosomes, numbers 12, 15, 16, 17, 18 and 19, can have an NOR. The number and distribution of chromosomes with NOR's vary among inbred strains of Mus musculus musculus (C57BL/6J, BALB/cJ, C3H/HeJ and C3H/StCpr1BR) and in M. musculus molossinus. In a musculus X molassinus F1 hybrid, nucleolus organizers from each parent are silver stained.--Chromosomes which have NOR's in diploid cells also show them in tetraploid cells and in established cell lines. The BALB/cJ strain shows Ag-staining of NOR's on chromosomes 12, 15, 18 and occasionally 16. In the RAG cell line, which was derived from BALB/c, active NOR's are seen on 12, 15 and 18, even after these chromosomes have undergone structural rearrangements in the cell line. Some correlation exists between the amount of Ag-stain and the size of a secondary construction region, with a large amount of Ag-stain present on a chromosome which has a prominent secondary constriction. There is no correlation between the amount of Ag-stain and the presence or absence of C-band material.

Total aneuploidy and age-related sex chromosome aneuploidy in cultured lymphocytes of normal men and women

Abstract: In PHA-cultured lymphocytes, about 8% of metaphases from 32 women were aneuploid compared to 4% of metaphases from 35 men A significant part of this aneuploidy was characterized by sex chromosome involvement: in women, the loss or gain of X chromosomes; in men, the gain of X chromosomes and the loss or gain of Y chromosomes The incidence of this aneuploidy was positively age-related for both sexes Premature division of the X-chromosome centromere was closely associated with X-chromosome aneuploidy in women and men, and appeared to be the mechanism of nondisjunction causing this aneuploidy Premature centromere division (PCD) indicated a dysfunction of the X-chromosome centromere with aging, and this dysfunction was the basic cause of age-related aneuploidy A similar mechanism of nondisjunction may operate for the Y chromosome of men, but could not be clearly demonstrated because of the low incidence of Y-chromosome aneuploidy

Chromosome mapping of the genes that control differentiation and malignancy in myeloid leukemic cells

Abstract: The chromosome banding pattern has been analyzed in clones of mouse myeloid leukemic cells that differ in their ability to be induced to differentiate by the protein inducer MGI (macrophage and granulocyte inducer). None of the clones had a completely normal diploid banding pattern. The clones studied were either MGI+ (that can be induced to form Fc and C3 rosettes), a stage in the differentiation of myeloid cells, or MGI- (that cannot be induced to form these rosettes). All six cultured clones of MGI- cells from myeloid leukemias independently produced in six separate animals showed a loss of a piece of one chromosome 2 and this abnormal chromosome was maintained in leukemias derived from the cultured cells. This loss was not found in MGI+ clones or lymphoid leukemias. Five MGI+ mutants, derived from an MGI- clone with a loss of a piece of one chromosome 2, one normal chromosome 12, and two translocated chromosomes 12, maintained the abnormal chromosome 2 but lost either the one normal or one of these translocated chromosome 12. These results indicate that chromosomes 2 and 12 carry genes that control the differentiation of myeloid leukemic cells and that inducibility by MGI is controlled by the balance between these genes. We suggest that these chromosomes also carry genes that control the malignancy of these cells.

Gene transfer by means of cell fusion I. Statistical mapping of the human X-chromosome by analysis of radiation-induced gene segregation

Abstract: Hybrid cells were obtained by virus-induced fusion of hamster cells with irradiated human cells. The analysis of such hybrids permits a study of the effects of lethal doses of radiation on human cells and provides a method of sub-chromosomal genetic mapping that is independent of karyological analysis. Radiation-induced chromosome exchanges are shown to be extremely localized, and a map of 4 X-linked genes is presented.

Chromosomal analysis of ddt-resistance in a long-term selected population of drosophila melanogaster

Abstract: The genetic basis of DDT-resistance was studied in a population of Drosophila melanogaster. This population was unique in that it had been continually selected for DDT-resistance since 1952 and had achieved a very high level of resistance. The genetic basis of resistance was studied by means of a chromosomal analysis. Fifteen combinations of resistant and control chromosomes were tested using a time-based DDT test. The analysis of the data showed that resistance was multifactorial with each of the three major chromosomes involved. Dominant and recessive second and third chromosome effects were found to be much more important than those of the first chromosome, which had no detectable recessive effects. Second and third chromosome resistance genes showed incomplete dominance. The average dominance of the second chromosome was much less than that of the third chromosome. These large-scale differences between chromosomes' effects and average dominance may indicate that a small number of resistance genes are involved. Two significant interactions between chromosomes were found. Scaling difficulties make the interactions difficult to interpret without further data. It seems possible that positive interactions between resistance have been developed by the long-term directional selection in this population.

Replication of prophage P1 during the cell cycle of Escherichia coli.

Abstract: We have followed, by DNA-DNA hybridization, the variation in the number of copies of prophage P1 relative to two chromosomal markers when the doubling time of the host cells is modified by a change in carbon source. The ratio of P1/chromosome terminus undergoes a twofold decrease when the cell doubling time increases from 24 to 215 min, whereas the ratio of P1/chromosome origin increases 1.4 fold; both ratios tend towards unity at slow growth rates. This suggests that the replication of prophage P1 is not simultaneous with chromosome initiation or chromosome termination. The chromosome replication time is unaffected by the presence of P1, and remains constant over the range of doubling times studied, with a value of about 4o min. Following amino acid starvation, the P1/chromosome origin ratio increases from 0.7 to 0.9, suggesting that P1 retains the ability to replicate after chromosome initiation has stopped and in the absence of essential amino acids. The results are discussed with reference to similar studies done on F and R1.

Chromatin and chromosome structure

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Activation of mouse ribosomal RNA genes at the 2-cell stage.

Abstract: The Ag-AS method, developed by Goodpasture and Bloom (1975) stains transcriptionally active nucleolus organizer regions (NORs) on the chromosomes and in the interphase nuclei. Metaphases and interphase nuclei of early mouse embryos (unfertilized eggs, pronucleus stages, 2-, 4-, 8-cell stages, and morulae) were subjected to silver-staining. First staining of a single chromosome bearing an NOR was observed at the 2-cell stage. At the 4-cell stage 4–6 chromosomes, and at the 8-cell stage invariably all the 6 chromosomes known to bear NORs, respond positively to silver-staining. These results indicate that during mouse embryogenesis ribosomal RNA genes start to function at the 2-cell stage. The polar body does not respond to silver-staining, which supports the view that the polar body genome remains inactive.

N banded karyotypes of wheat species

Abstract: Nine of the twenty-one chromosome pairs of the hexaploid wheat Triticum aestivum var. Chinese Spring (genome constitution AABBDD) show distinctive N-banding patterns. These nine chromosomes are 4A, 7A and all of the B genome chromosomes. The remaining chromosomes show either faint bands or no bands at all. Tetraploid wheat, T. dicoccoides (AABB), showed banded chromosomes similar to those observed in the hexaploid. Of the diploid species T. monococcum, T. boeoticum, T. urartu and Aegilops sauarrosa showed little or no banding as would be expected of donors of the A and D genomes. Ae. speltoides had a number of N-banded chromosomes as would be expected of a candidate for the B genome donor. Since N-bands are not evident on some nucleolar organiser chromosomes, the staining specificity cannot be correlated with the presence of nucleolar organiser regions.

Assignment of the genes for thymidine kinase and galactokinase to Mus musculus chromosome 11 and the preferential segregation of this chromosome in Chinese hamster/mouse somatic cell hybrids.

Abstract: Somatic cell genetic techniques were used to establish linkage assignments for the loci coding for galactokinase (GLK) and thymidine kinase (TK) in the laboratory mouse, Mus musculus.Four fusion experiments produced cell hybrids that segregated mouse chromosomes. Three series of hybrid clones were produced from the fusion of mouse macrophages or fibroblasts and Chinese hamster cells of the E36 line, which is deficient in hypoxanthine phosphoribosyltransferase activity. Clones were assayed for the expression of 11 mouse isozymes coded by genes on 11 chromosomes. Ten isozymes were retained at high frequencies, but the mouse GLK phenotype was absent in most primary clones and all secondary clones. Chromosome analysis of 24 of these hybrids indicated that GLK activity was lost concordantly with chromosome 11. One hybrid clone was produced from the fusion of peritoneal macrophages and hamster cells of the a3 line, which lacks TK activity. Mouse GLK activity was expressed in this primary clone and all secondary clones isolated in HAT medium, and was lost in all secondary clones backselected in medium with 5-bromodeoxyuridine. Thus, the genes coding for GLK and TK are syntenic and both can be assigned to chromosome 11. The absence of chromosome 11 in the related series of a3 hybrids, and its rapid segregation in 3 series of E36 hybrids, suggests that it carries a third locus (or loci), the retention of which is detrimental to Chinese hamster/mouse hybrids.

Chromosomes and causation of human cancer and leukemia. XXII. Karyotypic changes in malignant melanoma

Abstract: Detailed karyotypic analysis with G- and C-banding has been performed on cells of four malignant melanomas. The modal number in two cases was in the hypodiploid range, the chromosome numbers varying from 39 to 43. These two tumors had 5 to 13 marker chromosomes. The other two tumors were in the polyploid range, with modal numbers of 63 to 157 chromosomes. The cells had a minimum of 11 and a maximum of 40 marker chromosomes. Chromosome no. 1 was more frequently involved in aberrations than any other chromosome. The most common breakpoints on this chromosome were 1q21, 1q25 and 1q32. Frequent breakpoints were also noticed in the centromeric region in various chromosomes. In chromosome no. 1, however, the centromeric area does not seem to be involved. The more common breakpoints on the various chromosomes were 1q21, 1q25, 1q32, 5p13, 9q13, 11q23, 12q13. No common markers were noticed among these four cases of melanoma, but are noticed in unrelated tumors.

Why plant chromosomes do not show G-bands.

Abstract: Giemsa techniques have refused to reveal G-banding patterns in plant chromosomes. Whatever has been differentially stained so far in plant chromosomes by various techniques represents constitutive heterochromatin (redefined in this paper). Patterns of this type must not be confused with the G-banding patterns of higher vertebrates which reveal an additional chromosome segmentation beyond that due to constitutive heterochromatin. The absence of G-bands in plants is explained as follows: 1) Plant chromosomes in metaphase contain much more DNA than G-banding vertebrate chromosomes of comparable length. At such a high degree of contraction vertebrate chromosomes too would not show G-bands, simply for optical reasons. 2) The striking correspondence of pachytene chromomeres and mitotic G-bands in higher vertebrates suggests that pachytene chromomeres are G-band equivalents, and that this may also be the case in plants. G-banded vertebrate chromosomes are on the average only 2.3 times shorter in mitosis than in pachytene; the chromomeric pattern therefore still can be shown. In contrast, plant chromosomes are approximately 10 times shorter at mitotic metaphase; their pachytene-like arrangement of chromomeres is therefore no longer demonstrable.

A unique cytogenetic system in monotremes

Abstract: All 3 extant genera of monotremes show a unique kind of cytogenetic system involving the formation of a structurally heterozygous chain multiple apparently coupled with a system of complementary gametic elimination. In the echidna Tachyglossus there are 63 chromosomes in the male and 64 in the female. This is associated with an X1X2Y♂/X1X1X2X2♀ sex chromosome system. Additionally in both sexes there are 6 mitotic chromosomes (a-f) which have no obvious homologous partners. At male meiosis these are included with the 3 sex chromosomes in a chain multiple of nine which has the constitution X1·Y·X2·f·e·d·c·b·a. This shows convergent orientation at first metaphase leading to the production of two kinds of sperm, namely X1X2 eca and Yfdb. Since no individual of either sex has been found homozygous for any of the a-f elements it follows that only gametes carrying different combinations of the three unpaired elements give rise to viable offspring. Whether this depends on gametic selection or on zygotic lethality is not known. An apparently identical system operates in Zaglossus. In the platypus Ornithorhynchus, on the other hand, there are 52 chromosomes in both males and females associated with an XY♂/XX♀ sex chromosome mechanism and the presence of 4 consistently unpaired elements (a-d) at mitosis. A chain multiple of 10 forms at male meiosis involving the 2 sex chromosomes, the 4 unpaired elements and two of the small pairs of autosomes. Additionally the six longest autosome pairs in Tachyglossus and the X1 show a polymorphism for size which in heterozygous combination leads to the formation of unequal bivalents at male meiosis.

Gene transfer by means of cell fusion. II. The mapping of 8 loci on human chromosome 1 by statistical analysis of gene assortment in somatic cell hybrids

Abstract: A method is described which should permit determination of the order and spacing of genes on all human chromosomes by the analysis of just one set of man-mouse hybrid cells. This method is used to determine the map of 8 loci on human chromosome I. A comparison of the statistical maps of chromosome I and of the X-chromosome with the cytogenetic maps of these chromosomes at metaphase indicates that the statistically derived distances between genes are related to the amount of Giemsa light-band material between the genes.

Xg groups and sex chromosome abnormalities in people of northern European ancestry: an addendum.

Abstract: A catalogue of the Xg groups of 1547 patients with various abnormalities of number or of form of their sex chromosomes, together with the groups of many of their parents, appeared in this journal in 1971 (Sanger et al., 197 1a). All the Xg tests were done in the MRC Blood Group Unit and covered the time from the recognition of the Xg groups (Mann et al., 1962) to January 1971. The results were given in 8 tables. The purpose of the present communication is to record that the count was brought up to October 1975 by the addition of 536 more patients and that the revised 8 tables are available on request. The tables give the totals and analysis of the Xg groups of the following classes of propositi and their available parents: Table 1, 739 propositi with Klinefelter's syndrome; Table 2, parents of 566 XXY propositi; Table 3, 56 XX male propositi and their parents; Table 4, 975 propositi with Turner's syndrome; Table 5, parents of 610 of the Turner propositi; Table 6, 313 propositi with other kinds of sex chromosome abnormalities; Table 7 parents of 29 females with one X lacking a long arm; Table 8, normality of the Xg distribution in both parents of 647 assorted propositi. Here follow only a few notes prompted by the increased numbers. The Xg phenotype frequencies for normal northern Europeans are: for males Xg(a+) 0-659 and Xg(a-) 0 341; and for females Xg(a+) 0-884 and Xg(a-) 0 1 16 (Sanger et al., 1971b).