Showing papers on "Wild type published in 1978"
TL;DR: Genetic studies indicate that the mutants each carry a single recessive mutation responsible for the defective osmotic avoidance behavior, and preliminary anatomical studies indicate selective sensory neuron changes in at least one mutant.
Abstract: A wild-type strain of the nematode Caenorhabditis elegans has been shown to avoid high concentrations of a number of sugars and salts. Individual and population assays for this response were developed and mutants were selected for their inability to avoid high concentrations of fructose or NaCl. Seven nonavoiding mutants representing six complementation groups were isolated and characterized. Genetic studies indicate that the mutants each carry a single recessive mutation responsible for the defective osmotic avoidance behavior. The map locations of the six complementation groups identified by these mutations have been determined. Mutants isolated for their inability to avoid fructose are also unable to avoid NaCl and vice versa. The mutants move normally, exhibit normal touch sensitivity, and, like wild type, follow isotherms in a radial thermal gradient. All of the mutants are at least partially defective in the attraction to sodium chloride exhibited by wild type. None of the mutants is temperature sensitive, and all exhibit defective osmotic avoidance behavior as young L1 larvae. Preliminary anatomical studies indicate selective sensory neuron changes in at least one mutant.
265 citations
TL;DR: One or both of the toxin substrates thus appears to be involved in regulation of adenylate cyclase by guanyl nucleotides and fluoride ion.
254 citations
TL;DR: The failure of the mal T + product to repress the constitutive expression resulting either from a mal T c mutation or from initiator constitutive mutations strongly suggests that, in contrast to the l -arabinose system, the maltose system is regulated in a strictly positive manner.
157 citations
TL;DR: The apparent identity of wild-type and mutant products indicates that the deletion in NG-18 lies outside of the region encoding this major T antigen species, which appears that comigrates with that of the wild- type virus.
Abstract: When isolated by means of an anti-polyoma tumor (T) antiserum, the major product from mouse cells productively infected by wild-type polyoma virus is a polypeptide of 100,000 apparent molecular weight as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. In cells infected by NG-18, an hr-t mutant carrying a deletion of about 150 base pairs in the early region of the viral DNA, a T antigen species appears that comigrates with that of the wild-type virus. Comparisons of peptides after partial proteolysis reveal no differences between mutant and wild-type products. Both wild-type and mutant 100,000 products can be labeled in vivo with [32P]orthophosphate. An independent and more reliable estimate of the molecular weight of this protein using guanidine/Sepharose chromatography yields a value of 81,000 for both mutant and wild-type species. The apparent identity of wild-type and mutant products indicates that the deletion in NG-18 lies outside of the region encoding this major T antigen species.
Immunoprecipitates from wild-type infected cells shows four bands in addition to the “100,000” band; these have apparent molecular weights of 63,000, 56,000, 36,000, and 22,000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis; the 56,000 and 36,000 species are phosphorylated. All four of these lower molecular weight bands are absent or drastically reduced in the immunoprecipitates from NG-18-infected cells.
143 citations
TL;DR: Viable mutants of simian virus 40 with deletions in three regions of the virus genome with defective transforming ability are tested and retain their defect when tested in Chinese hamster lung cells and when infection is initiated with viral DNA instead of intact virions.
Abstract: Viable mutants of simian virus 40 with deletions in three regions of the virus genome (map coordinates 0.21-0.17, 0.59-0.54, and 0.67-0.74) have been tested for their ability to transform rat fibroblasts to anchorage independence. Only those mutants whose deletions occur between 0.59 and 0.55 in the proximal part of the early region are defective in transforming ability. The most severely defective of these transform with less than one-hundredth the efficiency of wild type. They retain their defect when tested in Chinese hamster lung cells and when infection is initiated with viral DNA instead of intact virions. Complementation for transformation can be observed between these transformation-defective deletions and a simian virus 40 temperature-sensitive A mutant.
133 citations
TL;DR: Analysis of the Lac+ recombinant formed by the various mutants indicated that they were identical to the recombinants formed by a wild-type strain, indicating that genetic recombination in E. coli is a highly regulated process involving multiple gene products.
Abstract: Escherichia coli strains containing mutations in lexA, rep, uvrA, uvrD, uvrE, lig, polA, dam, or xthA were constructed and tested for conjugation and transduction proficiencies and ability to form Lac+ recombinants in an assay system utilizing a nontandem duplication of two partially deleted lactose operons (lacMS286phi80dIIlacBK1). lexA and rep mutants were as deficient (20% of wild type) as recB and recC strains in their ability to produce Lac+ progeny. All the other strains exhibited increased frequencies of Lac+ recombinant formation, compared with wild type, ranging from 2- to 13-fold. Some strains showed markedly increased conjugation proficiency (dam uvrD) compared to wild type, while others appeared deficient (polA107). Some differences in transduction proficiency were also observed. Analysis of the Lac+ recombinants formed by the various mutants indicated that they were identical to the recombinants formed by a wild-type strain. The results indicate that genetic recombination in E. coli is a highly regulated process involving multiple gene products.
124 citations
TL;DR: A mutant deficient in cardiolipin synthesis is isolated and has no distinctive phenotype regarding its growth properties, membrane-associated respiratory functions, or the ability to insert bacteriophage M13 coat protein into the cell envelope.
120 citations
TL;DR: Results suggest that 1,2-diglyceride is the true substrate for the Kinase in vivo and that the kinase functions as a minor route for phosphatidic acid synthesis.
96 citations
TL;DR: The finding that mutant C3 no longer formed an initiation complex suggests that the interaction of the ribosome binding site with fMet-tRNA plays an essential role in the formation of the 70 S initiation complex.
94 citations
TL;DR: The results suggest that the A gene product of polyoma regulates transcription of early RNA, as has been suggested for SV40, and that the wild-type A-gene product overcomes the effect of the temperature-sensitive A-Gene product.
94 citations
TL;DR: A new procedure is described for the preparation of in vitro cell cultures from individual early gastrulae of Drosophila melanogaster, and it is proposed that this technique may be used to analyse abnormalities of cellular development in embryonic lethal mutants.
Abstract: Results are reported from the culturing in vitro of cells from individual early gastrulae of the following four groups of X-linked embryonic lethal mutants of Drosophila melanogaster . (1) Notch lethals. Five Notch mutants were studied which have been reported to give similar abnormalities in whole embryos: the nervous system displays a three-fold hypertrophy as part of a shift in the pattern of differentiation within ectodermal derivatives, and mesodermal derivatives do not differentiate. An hypertrophy of nerve was found in cell cultures prepared from embryos of all five mutants. In addition, four of the five alleles consistently gave abnormalities of muscle differentiation: when compared to controls, Notch cultures had a reduced frequency of myotubes, and displayed unusual clusters of myocytes which had either failed to fuse or had fused incompletely. Results from mixed cultures prepared from two embryos were consistent with the autonomous expression of nerve and muscle abnormalities by Notch -8 cells in the presence of wild-type cells. It is argued that the Notch locus has a direct role in the differentiation of both nerve and muscle. (2) white deficiencies. Cells carrying either of two deficiencies gave a clear-cut pattern of abnormalities: initial cellular differentiations were normal, but nerve, muscle and fat-body cells progressively deteriorated during the culture period. Mixed cultures showed that wild-type cells could not ‘rescue’ mutant muscle and fat-body cells; however, the status of the autonomy of mutant nerve abnormalities in these cultures was unclear. Both white deficiencies remove cytological band 3C1, and this permits a comparison of results with those from cultures of cells from Notch-8 embryos (also deficient for 3C1). Abnormalities displayed in cultures of the two types of mutant show no overlap. Therefore no consistent cellular abnormality can be attributed to absence of band 3C1. (3) lethal{l)myospheroid . In contrast to earlier observations on in vitro cell cultures (Donady & Seecof, 1972) muscle was seen to differentiate, though its morphology was extremely abnormal. Observations indicated that all cell types within the cultures had poor properties of adhesion to a glass substrate. It is argued that the observed abnormalities are not consistent with a mutant lesion which is restricted to the basement membrane ( contra Wright, 1960), and that all cell types carry a basic defect which may reside in the cell membrane. (4) shibirets alleles. Cultures of two temperature-sensitive lethal shibire alleles ( shits1, shits3 ) were normal at the permissive temperature of 22 °C. At the restrictive temperature (29 °C) early cell differentiation was normal but subsequent development was blocked. This blockage could be partially reversed by shifting cultures to the permissive temperature after as much as 10 days exposure to the high temperature. It is suggested that shits cells are mutant in a process which is basic to several cell types.
TL;DR: The precursor cells which give rise to the ventral nerve cord have been studied in lin-5 and in the mutant these precursors accumulate approximately six times the diploid quantity of DNA within a single nucleus, while attempting mitosis up to three times.
TL;DR: In this paper, the authors described a mutant of Toxoplasma gondii that was 100-fold more resistant to 5-fluorodeoxyuridine, as measured by growth in human fibroblast cultures.
TL;DR: Yeast sterol mutants exposed to crystal violet demonstrated greater dye uptake than the wild type and exposure for 10 min to hypertonic cation solutions showed a greater decrease in cell viability for mutants than for wild type.
Abstract: Yeast sterol mutants exposed to crystal violet demonstrated greater dye uptake than the wild type. In addition, exposure for 10 min to hypertonic cation solutions showed a greater decrease in cell viability for mutants than for wild type.
TL;DR: Two mutant strains of Rhizobium japonicum used in commercial inoculants were mutagenized and screened by a rapid effectiveness assay with soybean plants and expressed greater symbiotic nitrogen-fixing activity than the wild type in the presence and absence of fixed nitrogen.
Abstract: A strain of Rhizobium japonicum used in commercial inoculants was mutagenized and screened by a rapid effectiveness assay with soybean plants Two mutant strains nodulated the roots earlier than the wild type and also expressed greater symbiotic nitrogen-fixing activity than the wild type in the presence and absence of fixed nitrogen In addition, one of the mutants formed more root nodules than the wild type Plants inoculated with these strains had increased dry weights ( approximately 60 percent) and nitrogen content ( approximately 100 percent) when grown in growth chambers
TL;DR: Five new mutants were isolated on the X-chromosome which prevent or substantially delay puparium formation and subsequent metamorphosis without affecting larval development and could not be induced to pupariate by the implanted wild type ring gland.
Abstract: Five new mutants were isolated on the X-chromosome which prevent or substantially delay puparium formation and subsequent metamorphosis without affecting larval development. The mutant phenotype probably involves stage-specific gene functions unimportant for the larval development but vital for puparium formation and for the beginning of metamorphosis. Two mutants gave larval-puparial gynanders (LPG) and could not be induced to pupariate by the implanted wild type ring gland. The block in these is possibly in some ecdysone-inducible autonomous functions of the larval hypoderm. The other 3 mutants did not form LPG while the implanted wild type ring gland induced pupariation. These mutants presumably have a low, subthreshold amount of ecdysone which is not able to induce pupariation.
TL;DR: Some of the results seem to show that MATI and MATII are associated in vivo, which can be taken as an indication that Saccharomyces cerevisiae possesses two isoenzymatic methionine adenosyl transferases (MAT).
Abstract: Mutants requiring S-adenosyl methionine (SAM) for growth have been selected in Saccharomyces cerevisiae. Two classes of mutants have been found. One class corresponds to the simultaneous occurrence of mutations at two unlinked loci SAM1 and SAM2 and presents a strict SAM requirement for growth on any medium. The second class corresponds to special single mutations in the gene SAM2 which lead to a residual growth on minimal medium but to normal growth on SAM supplemented medium or on a complex medium like YPGA not containing any SAM. These genetic data can be taken as an indication that Saccharomyces cerevisiae possesses two isoenzymatic methionine adenosyl transferases (MAT). In addition, SAM1 and SAM2 loci have been identified respectively with the ETH-10 and ETH2 loci previously described. Biochemical evidences corroborate the genetic results. Two MAT activities can be dissociated in a wild type extract (MATI and MATII) by DEAE cellulose chromatography. Mutations at the SAM1 locus lead to the absence or to the modification of MATII whereas mutations at the SAM2 locus lead to the absence or to the modification of MATI. Moreover, some of our results seem to show that MATI and MATII are associated in vivo.
TL;DR: A mutant of 3T6 (mouse) cells previously selected for a loss of adenosine kinase also proved to be resistant to adenine arabinoside, the active form of T. gondii.
Abstract: We have previously reported the isolation and preliminary characterization of a mutant of Toxoplasma gondii that was resistant to adenine arabinoside. Fiftyfold higher concentrations of adenine arabinoside were required to inhibit the growth of the resistant parasite in human fibroblast cultures. To determine the enzymic basis for resistance, we measured the kinases and deaminases that act on adenosine or deoxyadenosine. All of these enzymic activities were found in uninfected human fibroblast cells. The mutant and wild type parasite proved to have similar activities of adenosine deaminase, deoxyadenosine deaminase, and deoxyadenosine kinase. However, the adenine arabinoside resistant mutant had less than 0.1% of the adenosine kinase activity observed in the wild type T. gondii. The mutant parasite is presumably resistant because without adenosine kinase to phosphorylate adenine arabinoside it cannot carry out the first step in the conversion of the analogue to adenine arabinoside triphosphate, the active form. A mutant of 3T6 (mouse) cells previously selected for a loss of adenosine kinase also proved to be resistant to adenine arabinoside.
TL;DR: Non-nodulating mutant strains of Rhizobium japonicum lacked a surface antigen that was present on the wild type that is associated with the O antigen portion of the lipopolysaccharide.
Abstract: Non-nodulating mutant strains of Rhizobium japonicum lacked a surface antigen that was present on the wild type. This surface antigen is associated with the O antigen portion of the lipopolysaccharide. Paper chromatography of hydrolyzed lipopolysaccharide and O antigen revealed three major component differences between the non-nodulating strains and the wild type.
TL;DR: The retention of malate-driven ATP synthesis in the absence of a significant pH gradient or electrical potential suggests that an alternative intermediate is involved in coupling oxidation to phosphorylation.
TL;DR: The results support previous reports that increased frequency of beating and ciliary reversal seen in response to depolarization both require the entry of Ca2+ through the surface membrane and indicate that frequency increase with hyperpolarization is independent of an altered rate of Ca 2+ entry.
Abstract: 1. The role of the surface membrane in the control of ciliary beat frequency in Paramecium was examined by intracellular electrophysiological techniques and pressure injection of Ca2+ and EGTA. Experiments were done on wild type P. caudatum and on both the wild type and a pawn mutant of P. tetraurelia. 2. The increased frequency of beating that accompanies reversal of power stroke orientation in response to depolarization in the wild type fails to occur during depolarization in the mutant pawn, which also fails to exhibit ciliary reversal upon depolarization. 3. Injection of moderate amounts of EGTA blocked the frequency increase without interfering with reversal of the beat in response to depolarization of the wild type. Larger injection of EGTA also prevented reversed beating. 4. The beat frequency in the normal (forward-swimming) direction increased during hyperpolarization in pawn. The hyperpolarizing frequency-voltage relations were quantitatively similar to those of the wild type. 5. Injection of EGTA to a final concentration of 10 mM into wild type cells neither modified the resting frequency nor blocked the frequency increase which normally accompanies hyperpolarization. 6. Transient ciliary reversal in both pawn and wild type produced by injection of Ca2+ could be terminated by the passage of inward current. The power stroke returned to the normal forward-swimming direction and the ciliary beating frequency increased. Upon termination of the inward current the cilia of Ca2+-injected cells again beat in reverse for many seconds. 7. The results support previous reports that increased frequency of beating and ciliary reversal seen in response to depolarization both require the entry of Ca2+ through the surface membrane. On the other hand, the results indicate that frequency increase with hyperpolarization is independent of an altered rate of Ca2+ entry. 8. Increased frequency during hyperpolarization appears to be related more closely to electrotonic membrane current than to membrane potential. It is proposed that inward current might activate high frequency beating by altering the ionic environment of the axoneme within the restricted volume of the cilium by electrophoretic means.
TL;DR: Ouabain-resistant mutations in Chinese hamster cells have been quantitatively characterized and the frequencies of UV-induced mutations were directly correlated with cell survival, indicating a similar causal relationship between cell killing and mutation induction.
Abstract: Ouabain-resistant mutations in Chinese hamster cells have been quantitatively characterized. The mutation frequencies were found to be induced curvelinearly with treatments of increasing doses of ultraviolet light (UV). For the range of UV doses tested (5–20 J/m 2 ), the observed mutation frequency, Y , as a function of UV dose X , follows a curvilinear function, Y = (−28 + 13.37 X − 1.52 X 2 + 0.08 X 3 ) · 10 −6 . The frequencies of UV-induced mutations were directly correlated with cell survival, indicating a similar causal relationship between cell killing and mutation induction. Under the same experimental conditions, X-rays induced 6-thioguanine-, but not ouabain-, resistant mutations. UV-induced ouabain-resistant (oua r ) mutants exhibit a selection disadvantage. Their phenotypic expressions are modifiable by various agents. Wild type and 16 oua r mutants were compared with respect to their sensitivity to ouabain inhibition of 86 Rb uptake by whole cells. All the oua r mutants assayed are less sensitive to the drug than are wild-type cells. In the absence of ouabain, the Na + −K + -ATPase activities can be significantly higher or lower than that of the wild-type cells.
TL;DR: In this paper, a mutant of Dictyostelium discoideum, M31, was identified, which produces a reduced number of alpha-mannosidase-1 molecules per cell during the developmental program of the organism.
TL;DR: A circadian clock mutant of Neurospora crassa with a period length of about 25.8 hours (4 hr longer than wild type) has been isolated after mutagenesis of the band strain, and it is recessive in heterokaryons and grows at about 60% the rate of the parent band strain on both minimal and complete media.
Abstract: A circadian clock mutant of Neurospora crassa with a period length of about 25.8 hours (4 hr longer than wild type) has been isolated after mutagenesis of the band strain. This mutant, called frq-5 , segregates as a single nuclear gene, maps near the centromere on linkage group III, and is unlinked to four previously described clock mutants clustered on linkage group VII R (Feldman and Hoyle 1973, 1976). frq-5 differs from the other clock mutants in at least two other respects: (1) it is recessive in heterokaryons, and (2) it grows at about 60% the rate of the parent band strain on both minimal and complete media. Double mutants between frq-5 and each of the other clock mutants show additivity of period length-two long period mutants produce a double mutant whose period length is longer than either of the two single mutants, while a long and a short period double mutant has an intermediate period length. Although slow growth and long periodicity of frq-5 have segregated together among more than 300 progeny, slow growth per se is not responsible for the long period, since all the double mutants have the slow growth characteristic of frq-5 , but have period lengths both shorter and longer than wild type.
TL;DR: Although the Diprmarker seems to act dominantly in the parental CHO cells, its behavior in Dipr× Dip5hybrids (CHO × CHO) is recessive as measured by cell survival in presence of the toxin, a paradoxical behavior that may be due to a gene dosage effect.
Abstract: Stable mutants highly resistant to the protein-synthesis-inhibitor diphtheria toxin have been selected in Chinese hamster ovary (CHO) cells. Protein synthesis in extracts of mutant cells is resistant to the inhibitory action of diphtheria toxin, indicating that the lesion has affected the proteinsynthesis machinery. However, about 50% of the elongation factor-2 (EF-2) activity in the mutant cells can still be ADP-ribosylated by diphtheria toxin, and this remaining EF-2 activity is similar to that present in the wildtype cells. We suggest that this result is best explained by assuming that our CHO cells contain two functional copies of the EF-2gene, and that only one of the copies is altered in the mutants. According to this view, the mutated allele produces EF-2 resistant to A D P-ribosylation which is capable of supporting cell growth in the presence of diphtheria toxin. Although the Diprmarker seems to act dominantly in the parental CHO cells, its behavior in Dipr× Dip5hybrids (CHO × CHO) is recessive as measured by cell survival in presence of the toxin. This paradoxical behavior may be due to a gene dosage effect. Segregation studies from hybrids show that the Diprmarker segregates independently of the Emtrand Thgrmarkers indicating that the Diprlocus is not linked to either the Emtrlocus or to the X chromosome.
TL;DR: In this paper, a series of isogenic strains carrying either uvrD3, uvrE101, uveE100, uvE502 or recL152 were analyzed for sensitivity to ultraviolet light, increased spontaneous mutation frequency and ability to carry out host cell reactivation.
Abstract: A series of isogenic strains carrying either uvrD3, uvrD101, uvrE4, uveE100, uvrE502 or recL152 were analyzed for sensitivity to ultraviolet light, increased spontaneous mutation frequency and ability to carry out host cell reactivation. All strains showed similar levels of UV sensitivity and ability to carry out host cell reactivation. uvrD and uvrE mutants exhibited significant increases in spontaneous mutation frequency compared to wild type or recL152 strains. All the alleles were recessive in transconjugants carrying a wild type F′ plasmid. F′ plasmids carrying either uvrE502 or recL152 failed to complement any of the above alleles but did complement rep-3. Strains carrying polA12 and either recL152, uvrD3, uvrD101, uvrE4 or uvrE502 were conditionally lethal for growth and showed altered recombination properties at 37°.
TL;DR: Results indicate that the mutant is defective in alpha sub unit, suggesting that the uncA401 locus carries the structural gene for alpha subunit, and that this polypeptide plays an essential role in ATPase activity in F1 molecule.
Abstract: Inactive coupling factor ATPase (F1) was prepared from an uncoupled mutant (uncA401) of Escherichia coli. Reconstitution of ATPase activity was observed when alpha subunit from wild-type F1 was added to the dissociated inactive F1 and the mixture was dialyzed against buffer containing ATP and Mg2+. ATPase was also reconstituted when the mixture of alpha subunit (wild type) and crude extract from the mutant was dialyzed against the same buffer. These results indicate that the mutant is defective in alpha subunit, suggesting that the uncA401 locus carries the structural gene for alpha subunit, and that this polypeptide plays an essential role in ATPase activity in F1 molecule.
TL;DR: Two new mutant lines of Tetrahymena thermophila (T. pyriformis, syngen 1), each conferring resistance to a different agent, are described, and the traits show phenotypic assortment.
Abstract: Two new mutant lines of Tetrahymena thermophila (T. pyriformis, syngen 1), each conferring resistance to a different agent, are described. Resistance to cycloheximide and 6-methylpurine are each determined by dominant genes, ChxA2 and Mpr; the traits show phenotypic assortment. The method used to select these mutations, the critical importance of backcrossing to wild type following mutagenesis, and the utility of these marker genes in further mutagenic selection schemes and studies of the sexual cycle of Tetrahymena are noted.
TL;DR: It is concluded that the gam-1 mutation affects flagellar component(s) involved in establishing an effective, signal-generating agglutination reaction.
Abstract: The temperature-sensitive gametogenesis-defective mutant, gam-1 is sex-limited, expressed only in mating type minus (mt-), and can sexually agglutinate but not fuse at the restrictive temperature (35 degrees C) with gametes of wild type (wt) mt+. Thin-section, freeze-cleave, and scanning electron microscopy reveal that the gam-1 phenotype is dependent on both the temperature at which the cells undergo nitrogen starvation (and therefore gamete formation) and the temperature at which the cells are maintained during the 12 h before mating. Under all conditions of gametogenesis at 35 degrees C, each gam-1 cell produces a normal-appearing membrane-associated mating structure that fails to activate in response to flagellar agglutination. Varying with the conditions of gametogenesis, on the other hand, are the agglutination and signaling properties of the gam-1 flagella. The two mutant phenotypes displayed by gam-1 have been denoted gam-1-I and gam-1-II. An agglutination reaction involving gam-1-I cells does not result in activation of the wt mt+ mating structure. A more stable agglutination reaction, which can result in activation of the wt mt+ mating structure, is characteristic of gam-1-II cells, but because the gam-1 mt- mating sturcture still fails to activate, cell fusion is precluded. We conclude that the gam-1 mutation affects flagellar component(s) involved in establishing an effective, signal-generating agglutination reaction.