Showing papers on "Chromosome published in 1969"
TL;DR: A bifunctional highly fluorescent quinacrine mustard was shown to give chromosome breaks preferentially localized to heterochromatic chromosome regions (identifiable by cold treatment) in the M-chromosome.
300 citations
TL;DR: Analysis by deoxyribonucleic acid-mediated transformation indicates that anomalies in mapping in the group II region of the chromosome exist and these loci exist in a cluster between the hisA1 and argC4 loci.
Abstract: Many of the viruses which infect Bacillus subtilis require glucosylated polyglycerol teichoic acid for adsorption. These mutants can be divided into three classes on the basis of enzymatic defects and growth on galactose-minimal medium. Transduction with phage PBS1 reveals that two of these, gtaA and gtaB, are linked to hisA1, whereas the gtaC locus is linked to argC. Analysis by deoxyribonucleic acid-mediated transformation indicates that these loci exist in a cluster between the hisA1 and argC4 loci. Anomalies in mapping in the group II region of the chromosome exist. The basis of these anomalies is discussed.
148 citations
TL;DR: Four forms of mole rats with diploid numbers of chromosomes of S2, 54, 58, and 60, respectively, were found in Israel and the vicinity and are tentatively considered as sibling species, almost completely isolated by cytogenetic and possibly ethological mechanisms.
Abstract: Four forms of mole rats with diploid numbers of chromosomes of S2, 54, 58, and 60, respectively, were found in Israel and the vicinity. The differences between the chromosome sets are due to whole-arm (Robertsonian) changes and pericentric inversions. The geographic distribution of the different forms is contiguous. Only a few hybrid individuals have been discovered. These chromosome forms are tentatively considered as sibling species, almost completely isolated by cytogenetic and possibly ethological mechanisms. The weak dispersal powers of mole rats may have-contributed to a rapid fixation of adaptive homozygous chromosomal changes.
125 citations
TL;DR: According to their chromosome sets, various members of the fish family Cyprinidae can be classified into two groups, one having about 50 chromosomes, the other having about 100 as mentioned in this paper.
Abstract: According to their chromosome sets, various members of the fish family Cyprinidae can be classified into two groups, one of which has about 50 chromosomes, the other about 100. In the species endowed with 50 chromosomes, the DNA content per cell ranges from 20 to 38% of that of mammals; this variability is attributed to regionally confined duplications. In the group having about 100 chromosomes, the DNA values comprise about 50% of that of mammals; these species apparently are tetraploid as compared to the former group.
123 citations
TL;DR: Evidence is provided for the existence of Ter, a function which generates linear λ chromosome from structures in which the termini are linked, and specifically between genes R and A—the terminal genes of the mature chromosome.
Abstract: Bacterial strains lysogenic for two prophages in tandem undergo a special kind of prophage excision ("dilysogenic excision") which does not depend on the three known recombination mechanisms. This excision is specifically between genes R and A - the terminal genes of the mature chromosome. This is evidence for the existence of Ter, a function which generates linear λ chromosome from structures in which the termini are linked. © 1969 Nature Publishing Group.
111 citations
TL;DR: Somatic cell hybrids have been made between an established human cell line with a long culture history and established mouse fibroblast line and the number of human chromosomes is greater than in hybrids made from human diploid fibroblasts.
Abstract: Somatic cell hybrids have been made between an established human cell line with a long culture history and established mouse fibroblast line. When first analyzed, the hybrid cells contained nearly twice as many mouse chromosomes as the mouse parent line and a human chromosome complemnent of about half that of the human parent. There was further loss of human chromosomes on continued cultivation. This behavior resembles that of other human mouse hybrids and appears to be characteristic of the human-mouse combination. However, the number of human chromosomes is greater than in hybrids made from human diploid fibroblasts. Some clones contain more than a haptoid quantity of human DNA per cell and should synthesize a much greater number of human gene products.
93 citations
TL;DR: It is proposed that interruption of DNA replication, and consequent chromosome aberration, are the result of the inhibition of protein synthesis, and Cycling of cultured cells through amino acid deprivation is proposed as a technique for deliberately increasing the rate of chromosome alteration in genetic experiments.
90 citations
TL;DR: The results are taken to indicate that the virus initiates chromosomal DNA synthesis but that infection eventually results in extensive destruction of the cell genome, and thus the death of the cells.
85 citations
TL;DR: The results are consistent with the interpretation that the amount of satellite DNA in each chromosome is proportional to the total DNA of the chromosome and that it is not limited to a fixed amount per chromosome.
81 citations
TL;DR: The chromosome number of these cultures was determined, which could then be compared with those of the commercial hybrid to determine if a change had occurred in chromosome number, and this has implications in the use and interpretation of data from pathological, cytogenetical, biochemical, and physiological studies using cell cultures.
Abstract: A B S T R A C T Chromosome numbers of five Saccharum species hybrids and their cell suspension cultures were determined. The chromosome number was stable in four parental clones (2n = 122, 114, 114, and 112), but was variable in another (2n = 108-128). The cell suspension cultures have been maintained in a yeast extract-enriched nutrient medium for more than 6 years. These cultures were variable in chromosome number for all clones, with a partial aneuploid series at the haploid and/or polyploid level. Each clone had different chromosomal population modes after 6 years of culture. The loss of chromosomes over a period of time would have an effect on the genetic makeup of a cell population. This has implications in the use and interpretation of data from pathological, cytogenetical, biochemical, and physiological studies using cell cultures and is probably a partial explanation for the loss of totipotency in 6-year-old sugarcane tissue and suspension cultures. SUGARCANE CELL suspension cultures are being used at our experiment station in biochemical, physiological, cytogenetical, and pathological studies. The identification of suspension cultures with stable chromosome levels would be useful in the interpretation of certain phases of these studies. Suspension cultures of several commercial sugarcane hybrids have been maintained on the same medium, under the same conditions, for 6 years. The present study was undertaken to determine the chromosome number of these cultures, which could then be compared with those of the commercial hybrid to determine if a change had occurred in chromosome number.
TL;DR: Seven strains of HeLa cells have been characterized and it is suggested that human cell strains can be used for biochemical studies if they are cloned and if the clones are relatively stable at least with respect to modal chromosome number and karyotype.
Abstract: Seven strains of HeLa cells have been characterized by the number of chromosomes and the activity of the enzymes alkaline phosphatase, glucose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, and lactic dehydrogenase. All seven strains were found to differ as to chromosome numbers and enzyme levels despite the fact that two strains were called HeLa and three were called HeLa S3. Three strains were found to have a stemline in which greater than 60% of the cells demonstrated a single chromosome number, and this characteristic was stable for at least 6 months. A nomenclature for these clones has been suggested by the use of the stemline chromosome number as a subscript following HeLa. These three clones were, therefore, designated HeLa65, HeLa71, and HeLa75. Karyotypes were made of the stemlines of these clones and were compared with enzyme levels. Alkaline phosphatase showed the greatest variation from cell line to cell line with a 200-fold difference in levels, whereas glucose-6-phosphate dehydrogenase showed variation in activity over a 12-fold range, lactic dehydrogenase over an 8-fold range, and 6-phosphogluconic dehydrogenase over a 2-fold range. It is suggested that human cell strains can be used for biochemical studies if they are cloned and if the clones are relatively stable at least with respect to modal chromosome number and karyotype.
TL;DR: An allelism matrix of ethyl methanesulphonate-induced recessive recessive lethals found in a short chromosomal segment covered by the Y· mal + chromosome was constructed, which supports the view that most ethyl methamphetamineane-induced lethals were point-mutations.
Abstract: An allelism matrix of ethyl methanesulphonate-induced recessive lethals found in a short chromosomal segment covered by the Y· mal + chromosome was constructed. When allelism tests for the lethals were extended to X-ray-induced lethals, a consistent linear map of 34 functional units could be constructed. 80% of the chemically induced lethals comprised single sections, which supports the view that most ethyl methanesulphonate-induced lethals were point-mutations. Most X-ray-induced lethals that were multi-section lethals were aberrations. The distribution of mutations in the affteced units was highly non-random; consequently any pooling of sensitivity patterns for whole chromosome segments would be misleading. There were some “hot-spots”, possibly due to the vicinity of intercalary heterochromatin. There was also an excess of chromosomes with more than one lethal. The possibility that variation in specificity of lethal and visible mutations obtained with different mutagenic agents is a secondary function of the number of “essential sites” in “vital” and “non-vital” genes is discussed.
TL;DR: The Chromosomal location of genes for fertility-restoration, awnlessness, spelta-type ear and red coleoptile color of Triticum spelta var.
Abstract: Chromosomal location of genes for fertility-restoration, awnlessness, spelta-type ear and red coleoptile color of Triticum spelta var. duhamelianum, an effective fertility- restorer for the timopheevi cytoplasm, was determined by monosomic analysis. The results can be summarized as follows:T. spelta var. duhamelianum carries a dominant fertility-restoring gene Rf3 on its chromosome 1B. Chromosome 7D exerts a weak suppressing effect to this gene. Awnlessness is mainly due to an epistatic inhibitor B1 in chromosome 5A, while chromosome 6D has a promoting effect on awn development. As to the ear type, chromosome 5A carries a spelta gene q1, whereas chromosomes 2D and 3D possess some modifiers to this gene. Red coleoptile color is produced by genes in chromosomes 7A and 7D, while five other chromosomes, 2A, 2B, 2D, 3B and 6A, carry weak suppressors.
TL;DR: The development of methods for the investigation of chemical-induced chromosome damage is described using either bone marrow cells from rats and mice, or cultured rat leucocytes, and the application of these methods to 4 biologically active compounds is demonstrated.
Abstract: The development of methods for the investigation of chemical-induced chromosome damage is described using either bone marrow cells from rats and mice, or cultured rat leucocytes. The application of these methods to 4 biologically active compounds is demonstrated, and the value of such compounds as control materials for similar investigations is discussed.
TL;DR: Change in chromosome size in root tip meristems of rye and Allium cepa are induced by growing the plants in solutions differing in phosphorus content, and variation is a reflection of change in the chromosome dry mass.
Abstract: Change in chromosome size in root tip meristems of rye and Allium cepa are induced by growing the plants in solutions differing in phosphorus content. The chromosomes are 50% larger by volume in a “high” phosphate as compared with a “no” phosphate solution. Alteration of other elements supplied in culture also induces change in the size of chromosomes. — The size variation is a reflection of change in the chromosome dry mass. In part at least this change in mass is attributable to alteration in the amount of protein. The DNA component of the chromosomes remains unchanged. — A consistent pattern of change in chromosome size, quite independent of that induced by varying the culture solution, is related to age and development. For example, the root tip chromosomes double in size during the first three weeks of growth in rye seedlings. Thereafter the size decreases. As with the induced chromosome changes the protein content alters, the DNA amount remains constant. — Variation in the “non-permanent” component of the chromosomes in meristems appears to be closely correlated with the rate of cell metabolism.
TL;DR: A direct correlation was found between observed DNA absorbance and chromosome number except for plants of B. papyrifera with 84 somatic chromosomes, which may be an adaptation for the establishment of higher ploidy in birches.
Abstract: Relative amounts of DNA were determined on telophase nuclei by Feulgen cytophotometry for euploid taxa of birch (Betula) with somatic chromosome numbers of 28, 42, 56, 70, and 84. A direct correlation was found between observed DNA absorbance and chromosome number except for plants of B. papyrifera with 84 somatic chromosomes. The DNA density value for nuclei of the 84-chromosome plants fitted a 1∶2.25 ratio instead of the expected 1∶3.0 ratio. The DNA density value for these plants was calculated to be approximately equivalent to plants which would possess 63 somatic chromosomes. The average DNA value per chromosome was 2.73 for the 84-chromosome plants in contrast to 3.50 per chromosome in each of the lower euploids. Nuclear diameters of the 84-chromosome plants were directly related to chromosome number and not to DNA density value. The genomic number of Betula was considered to be x=7, rather than x=14, since a DNA value equivalent to 63 chromosomes is a multiple of 7 and not 14. Diploid birch species (2n=2x=28), therefore, would actually be tetraploids (2n=4x=28). The reduction in DNA content may be an adaptation for the establishment of higher ploidy in birches.
TL;DR: Considerable amount of experimental evidence has provided results consistent with the observational appearance of half-chromatids, and the effects of incorporated isotopes are expressed in generations succeeding labeling.
Abstract: Publisher Summary Various observational evidences indicate that chromosomes are multistranded. These observations are obtained by light microscopic studies on organisms containing large chromosomes. The two half-chromatids separate quite far from one another and can be found interwound over great distances along their length. In favorable material the separation can be found even in prophase and metaphase. Considerable amount of experimental evidence has provided results consistent with the observational appearance of half-chromatids. The evidence falls into five different categories dealing with (1) the types of aberrations induced in late prophase or metaphase by radiation, (2) the types of aberrations induced by radiation at the end of G 1 before the chromosomes have replicated, (3) experiments in which chromosome structure has been unraveled by treatment with enzymes or other agents, (4) the distribution of labeled DNA among the chromosomes at mitoses subsequent to labeling, and (5) experiments in which the effects of incorporated isotopes are expressed in generations succeeding labeling.
TL;DR: Results suggest that the origin and the terminus of the chromosome are associated with the membranes of Bacillus subtilis.
TL;DR: A genetic map of a large region of the chromosome of Hemophilus influenzae has been defined by transformation with high molecular weight DNA and a physical map was developed by the transfer of linked markers with specific sized pieces of donor DNA.
TL;DR: The DNA‐packing ratio, i.e., the length of DNA double helix per unit length of chromosomal fiber, appears to be much lower than in metaphase chromosomes derived from normal lymphocytes.
Abstract: Chromosomes of Burkitt's lymphoma cell line AL-1 were examined and measured by whole-mount quantitative electron microscopy after isolation by surface-spreading and critical point drying. The ultrastructure of the chromosomes is based entirely on twisted, irregularly folded fibers about 300 A in diameter. An acrocentric marker chromosome, exceeding all others in length, was seen to be connected to 13-15 chromosomes by common fibers. Dry mass values of 5 marker chromosomes from different metaphases ranged from 20.1 to 25.8 × 1O−13 g. Within each measured metaphase, the dry mass ratio of the marker to 13-15 chromosomes was 2.2 and of the marker to 21-22 chromosomes was 4.3. These ratios identify the marker in terms of dry mass as the missing number 2 chromosome. Average fiber dry mass was 11.2 × 10−16 g per micron. For one marker chromosome, total fiber length per chromatid was 1089 microns. Cross-sectional scans through the chromatids of this marker indicated 83 fiber equivalents in the centromere, 68 to 178 in the long arms, and 155 to 157 in the telomeres. On the assumption that the DNA content of the marker is equal to a chromosome 2, the DNA-packing ratio, i.e., the length of DNA double helix per unit length of chromosomal fiber, appears to be much lower than in metaphase chromosomes derived from normal lymphocytes.
TL;DR: Two molecular models of chromosome structure which have recently been put forward are consistent with observations and account for many cytogenetic, genetic and ultrastructural phenomena.
Abstract: IN all eukaryotic organisms so far investigated, the genomic DNA includes reiterated DNA sequences which are referred to as families of related base sequences1, and two molecular models of chromosome structure which have recently been put forward are consistent with these observations. Callan7's master–slave hypothesis2 has it that certain regions of the chromosomal DNA, especially those of the lateral loops of lampbrush chromosomes, are sequential reiterations of functionally equivalent gene sequences. Similarly, Beermann3 has proposed that the chromomere of the chromosome is a repository for families of similar but not necessarily identical genes. These models account for many cytogenetic, genetic and ultrastructural phenomena.
TL;DR: A phenotypically normal male mouse, investigated because it was sterile, was found to possess 41 chromosomes, and a karyotypic analysis indicated the extra element was one of the smallest chromosomes, almost certainly the Y.
Abstract: A phenotypically normal male mouse, investigated because it was sterile, was found to possess 41 chromosomes. A karyotypic analysis indicated the extra element was one of the smallest chromosomes, almost certainly the Y. X-Y bivalents, Y-Y bivalents and XYY univalents were seen in meiotic metaphase I cells, and it was therefore concluded that the extra chromosome was indeed the Y. Spermatogenesis tended to break down after meiosis I, but a few spermatids and sperm were observed.
TL;DR: The presence of a chromosome bearing a sub-terminal centromere within the complement of the Amazon molly provides the only direct evidence to date of centric shifts within the chromosome complements of the subgenus Poecilia.
Abstract: Cytological studies of fish from the subgenus Poecilia (Pisces) including members of an all-female species, P. formosa, have clearly shown diploid, somatic chromosome complements and Robertsonian arm numbers of 46. A triploid somatic chromosome complement of 3N = 69 was demonstrated for members of a naturally occurring variant clone of P. formosa, a form whose general body morphology closely resembles that of its sympatric species P. mexicana. Chromosomes of the different poeciliid species studied are remarkably similar in size, shape and structure, being mostly short acrocentrics, 2 μ long or less.The presence of a chromosome bearing a sub-terminal centromere within the complement of the Amazon molly provides the only direct evidence to date of centric shifts within the chromosome complement of the subgenus Poecilia. This finding also provides the first plausible cytogenetic basis for concluding that P. formosa is of relatively recent origin. Comparisons of relative chromosome lengths from both mitotic a...
TL;DR: Clinical and chromosome studies in a family in which two brothers suffer from Fanconi's aplastic anaemia and their sister has typical congenital abnormalities and chromosome changes without the anaemia are presented.
Abstract: A pernicious anaemia-like picture of the peripheral blood associated with congenital abnormalities was first described by Fanconi (1927) in three brothers. Since then a similar syndrome has been reported from many parts of the world under the title of Fanconi's aplastic anaemia. Gmyrek and Syllm-Rapoport (1964) have reviewed 152 cases in the literature in considerable detail. Bloom et al. (1966) described gross chromosome abnormalities which appear to be present in all patients with this peculiar anaemia so far tested. We present clinical and chromosome studies in a family (Fig. 1) in which two brothers suffer from Fanconi's aplastic anaemia and their sister has typical congenital abnormalities and chromosome changes without the anaemia.
TL;DR: The chromosomes of a Burkitt lymphoma case were followed through a period of three months, including stages before treatment and during treatment and progression, finding a difference characterized both the facial tumors and the neck metastases.
Abstract: The chromosomes of a Burkitt lymphoma case were followed through a period of three months, including stages before treatment and during treatment and progression. The patient had bilateral facial tumors with metastases to lymph nodes on either side of the neck. The chromosomal stemlines were different on the left and the right side. Both were diploid, the left side representing the normal karyotype, the right side exhibiting a number of marker chromosomes. This difference characterized both the facial tumors and the neck metastases.
During early stages of the right-side tumor, the marker chromosomes M2 and MC predominated. Both were derived from C group chromosomes and had a constriction on their longer arm, separating a distal segment from the rest of the chromosome. M2 had the appearance of a small No. 2 chromosome, MC that of a large C chromosome. Later on, M2 was replaced by M1 through translocation of the distal segment to a No. 1 chromosome. Two other marker chromosomes MB and MD resembled B and D chromosomes, respectively, with elongated long arms.
At terminal stages of the disease, when chemotherapeutic treatments had been administered repeatedly, highly disturbed chromosome conditions prevailed with numerous signs of chromosome breakage and errors of spiralization. Also a cultured cell line established at an early stage from the right-side tumor showed a high incidence of similar aberrations. All the marker chromosomes, except, M1, were recovered in the culture.
TL;DR: Cytogenetic analysis combined with blood grouping in a phenotypically abnormal child and his family suggest that the MN locus is in the long arm of either chromosome No. 2 or chromosomes No. 4.
Abstract: Summary. Cytogenetic analysis combined with blood grouping in a phenotypically abnormal child and his family suggest that the MN locus is in the long arm of either chromosome No. 2 or chromosome No. 4. The propositus, who is type M, appears to be hemizygous at the MN locus, or has a condition that cannot be distinguished from hemizygous by serological methods. The father, who is type N, is homozygous N/N by dosage estimations. The caryotype of the propositus is 46,XY,t(2q-; 4q +). About one-half of the distal part of the long arm of a No. 2 has been translocated to the distal end of the long arm of a No. 4.
TL;DR: The following conclusion may be reasonably drawn as far as wheat and its relatives are concerned: appreciable changes of DNA content might have resulted from chromosome aberrations accumulated in the course of genome differentiation of a common primitive genome at the diploid level.
Abstract: 1. Comparisons were made of DNA content per nucleus in common wheat, artificially synthesized 6x wheat, its parental species and three analyzers.2. DNA content per nucleus in the D genome analyzer was the lowest, B genome had a little lower DNA content than A genome, but the difference between the last two was not significant.3. Ssp. strangulata had a significantly higher DNA value than var. typica of the same species, Ae. squarrosa.4. Two strains of synthesized 6x wheat, ABD No. 1 and ABD No. 13, have nuclear DNA equal to the sum of the DNA contents of their respective parents. Nuclear DNA content of cultivated common wheat (Chinese Spring) is quite the same as that of synthesized 6x wheat, especially ABD No. 13.5. In three subspecies of T. aestivum, vulgare, spelta and macha no significant difference was found in DNA content per nucleus.6. Based on the above facts, the following conclusion may be reasonably drawn as far as wheat and its relatives are concerned:a) Appreciable changes of DNA content might have resulted from chromosome aberrations accumulated in the course of genome differentiation of a common primitive genome at the diploid level.b) The three different genomes, once established, have been appreciably stable and kept the amount of DNA constant either in diploid or polyploid condition.
TL;DR: Evidence supports the involvement of the homoeologues of the B and D genomes and the existence of isoenzymatic proteins which are capable of hybridization in the sub-tribe Triticinae.
Abstract: FOUR different manifestations of the concept of genetic similarity have been demonstrated in the sub-tribe Triticinae. Two of these are at the chromosome level and two are at the gene level. Sears1 demonstrated that each chromosome of hexaploid Triticum has two genetically related chromosomes which are undoubtedly of common origin. These related chromosomes or homoeologues can replace one another without causing serious genetic imbalance. This homoeology extends beyond Triticum to the genera Secale2, Agropyron3 and Aegilops4. Cytological similarity of chromosomes was established by Riley and Chapman5 when they demonstrated that particular non-homologous chromosomes of Triticum and of Triticum and Aegilops have the potential to pair or synapse with one another. Similarity at the phenotypic level of gene expression was examined in detail by Sears6 in his study of Neatby's virescent gene. He showed that there exist three genes affecting chlorophyll production in a similar manner. The three genes are carried on the three chromosomes of homoeologous group 3. We have demonstrated similarity at the level of enzymatic gene-products7 and the existence of isoenzymatic proteins which are capable of hybridization. These proteins are produced by a particular rye chromosome, its wheat homoeologue of the A genome and apparently the homoeologues of the other two wheat genomes. Recent evidence, which will be published in detail later, supports the involvement of the homoeologues of the B and D genomes. These four patterns of similarity are compatible with one another.
TL;DR: The experiments indicate that the human somatic chromosome is a multistranded structure that loosens in late G 1 to form functional chromatids.
Abstract: If cells are irradiated during most of the G 1 portion of the cell cycle, chromosome aberrations are produced. If, however, they are irradiated while in S or G 2 , chromatid aberrations are formed. The best estimate of when the transition occurs is late G 1 . That is, in both plant and animal cells, the chromosome splits into chromatids before DNA synthesis. This doubling of the chromosome conceivably could be caused by either a synthesis of chromosomal protein prior to S, or by a loosening of a multistranded struture. Experiments were carried out with phytohemagglutinin-stimulated human lymphocytes to test which of the two possible explanations cited above would be the more likely. Phytohemagglutinin-stimulated lymphocytes were cultured in the presence of 2·10 −3 M hydroxyurea and triated thymidine for 40 h. The hydroxyurea was used to inhibit DNA synthesis and to enrich the population of cells at the end of G 1 . Cells were then irradiated with 200 R of X-rays and recultured in the absence of tritium. When the cells reached metaphase, unlabeled cells were scored for the types of aberrations induced by the prior irradiation. Chromatid aberrations were found, indicating that in human cells, too, the split occurs in G 1 in the absence of DNA synthesis. Similar experiments in which the protein synthesis inhibitor cycloheximide was added after the cells were in culture for 16 h (before any DNA synthesis had occurred) and kept in until the fortieth hour showed that the transition occurred when protein synthesis was inhibited, too. The experiments indicate that the human somatic chromosome is a multistranded structure that loosens in late G 1 to form functional chromatids.