bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasmodium formation without change in nuclear DNA content inPhysarum polycephalum
Authors: Cooke D. J. , Dee Jennifer 
Published: September 2009

SUMMARYThe Colonia isolate ofPhysarum polycephalumproduces plasmodia within amoebal clones. Wheals demonstrated genetically that amoebae of the C50 strain of this isolate, when crossed with heterothallic amoebae, yielded recombinant progeny. He concluded that nuclear fusion and meiosis occurred in these crosses and suggested that nuclear fusion was also involved in plasmodia formation in clones. He thus designated the strain ‘homothallic’.In the present work genetic evidence is presented which indicates that the Colonia strainCL, when crossed with heterothallic strains, also yields recombinant progeny and thus undergoes nuclear fusion and meiosis. Microdensitometric measurements of nuclear DNA content are reported which indicate thatCLamoebae are haploid like heterothallic amoebae, and crossed plasmodia are diploid. However, clonally formedCLplasmodia were found to have the same G2nuclear DNA content asCLamoebae. This observation excludes the possibility of nuclear fusion when plasmodia form within clones ofCLamoebae and therefore the strain cannot be homothallic. Two alternatives, apogamy and coalescence, are proposed as the most likely mechanisms for clonal plasmodium formation in strainCL.
Genetic analysis of recombination at theglocus inSordaria fimicola
Authors: Whitehouse H. L. K. 
Published: September 2009

SUMMARYInterallelie crosses of mutants at thegrey(g) spore colour locus inSordaria fimicola, heterozygous for flanking markers, give rise to a large number of aberrant ascus genotypes, 45 of which can arise through relatively simple events and have been chosen for study. These genotypes comprise 50–75% of the aberrant asci, depending on the mutants crossed.Comparison of the results from 10 pairwise crosses involving 7 alleles reveals that linked postmeiotic segregation and co-conversion decrease rapidly in frequency with increasing separation of the mutant sites.The data from reciprocally recombinant asci, from asci with normal segregation at one of the two mutant sites, and from flanking marker behaviour in one- and two-point crosses, agree with the Holliday-Sobell formulation, with the following additional features:(1) The nuclease, which nicks homologous polynucleotides and then degrades one of the two nicked chains when a mutant enters the hybrid DNA structure, can show preferential degradation of the mutant (or the wild-type) chain. In addition, a second nuclease is involved in the excision-repair process that introduces an additional preferential (marker specific) bias in the degradation of the mutant (or the wild-type) chain. This could explain why asci with odd-ratio conversion (5:3 and 3:5 ratios) sometimes show a different bias, as first reported by Emerson forAscobolus, from those with even-ratio conversion (6:2 and 2:6 ratios), since the latter but not the former require, in addition, the action of a mismatch correction enzyme to account for them.(2) The migratory hybrid DNA structure which enters the gene at one end may be of a different size from that which enters from the other end.(3) Mismatch correction at the end of the hybrid DNA structure leads to a non-recombinant outside marker genotype and modifies the 1:1 ratio of parental:recombinant flanking markers that is otherwise found.
The independence of germ-cell genotype from somatic influence in chimaeric mice
Authors: McLaren Anne 
Published: September 2009

SUMMARYMouse chimaeras made by aggregating embryos homozygous for nine recessive genes with embryos carrying the corresponding dominants were mated with partners of the recessive strain. Progeny were either of the recessive type for all loci examined, or showed the dominant characters at all loci. Tail length in homozygous vestigial-tail progeny was unaffected by whether the fertilizing spermatozoon had undergone maturation in a chimaera or in a control vestigial-tail male. There was thus no indication that the germ cells had been in any way modified by their intimate association with germ cells and somatic tissue of contrasting genotype in the chimaeras.
Cytoplasmic mutations isolated from protoplasts ofPodospora anserina
Authors: Belcour Léon 
Published: September 2009

SUMMARYSorting out of cytoplasm determinants can be achieved inPodospora anserinaby the use of protoplasts. In this way four cytoplasmic mutations have been isolated. These mutations affect a precise stage of development of the fungus. In crosses with wild-type strains, the mutants show maternal inheritance when no cytoplasmic contact precedes fertilization. However, when cytoplasmic mixing occurs before fertilization, the cytoplasmic wild-type factor shows dominant and/or suppressive properties over the mutant factor.
An easy way of obtainingAspergillus nidulanshaploids in the parasexual cycle usingN-glycosyl polifungin
Authors: Bal Jerzy , Bartnik Ewa , Goryluk Bożenna , Pieniążek Norman J. 
Published: September 2009

SUMMARYA considerable improvement in the selection of haploids inAspergillus nidulansis described. Haploidization is used to assign genes to linkage groups (chromosomes) in fungi. The differential effect of a polyene antibiotic,N-glycosyl-polifungin, in respect to haploids and diploids, was utilized. In minimal medium only diploids (constructed from a ‘Master Strain’ and the investigated strain), which are fully heterozygous and thus have no growth requirements, germinate and are killed by the antibiotic. However, auxotrophic haploids, either induced or spontaneously formed, survive. These can then be used for linkage studies.
The characteristics of eleven mutants of R-factor R57 constitutive for tetracycline resistance, selected and tested inEscherichia coliK12
Authors: Reeve E. C. R. , Robertson J. M. 
Published: September 2009

SUMMARYEleven mutants of R-factor R57 have been isolated which show constitutive expression of resistance to tetracycline (Tc). These derepressed (Tdr) mutants all gave a much greater resistance to Tc and to its analogue, minocycline, than could be obtained by optimal induction of cells carrying the wild-type (T+) determinant. Cells carrying each of the Tdr mutants together with T+of either R6-S or of a plasmid found inEscherichia colimi19 showed inducible Tc resistance, indicating that the Tdr mutants were all recessive, i.e. of repressor-negative type. Tdr1 was not recessive to the T-determinant of RP1, suggesting that the repressor gene products of the T-determinants in R57 and RP1 have different specificities.
Mutant with heat-sensitive capacity for phagocytosis in tetrahymena: isolation and genetic characterization
Authors: Silberstein Gary B. , Orias Eduardo , Pollock Nina A. 
Published: September 2009

SUMMARYA mutant ofTetrahymenawith heat-sensitive phagocytosis was obtained using a tantalum-particle enrichment procedure. The mutant phenotype is most likely determined by a somatic (macronuclear) mutation(s). The inability of the mutant to sustain cell division and to phagocytize at 37 °C are most likely determined by the same mutation. The phenotype of the mutant is stably inherited under vegetative propagation at 30 °C. At 37 °C, the mutation affects the development of the oral apparatus, the phagocytotic organelle. This mutant has proven useful for the study of cellular functions related to phagocytosis.
Gene transfer inDrosophila melanogaster: genetic transformations induced by the DNA of transformed stocks
Authors: Fox Allen S. , Parzen Sheldon D. , Salverson Helen , Yoon Sei Byung 
Published: September 2009

SUMMARYDNA prepared from transformed stocks ofDrosophila melanogasterinduces second-step transformations resembling the original. The gross yield of transformants induced by transformed DNA is several times higher than that induced by the original allo-DNA, but much of this high frequency is attributable to a few exceptionally large clusters of transformants among flies treated with transformed DNA. When these large clusters are omitted from the data, the frequency of transformants induced by DNA from transformed stocks is the same as that induced by allo-DNA. The data therefore support the conclusion that the original DNA-induced alterations resulted from the transfer of genetic material capable of indefinite replication.
New compound (1) chromosomes and the production of large quantities of X/O males in Drosophila hydei
Authors: Beck H. 
Published: September 2009

SUMMARYIn view of the exceptional usefulness of Drosophila hydei for the analysis of Y-chromosome activity, a technique has been developed which permits the production of large numbers of males lacking a Y chromosome. It is based on the synthesis of new compound(1) chromosomes which carry sufficient rDNA genes to secure survival in the absence of any Y-chromosomal rDNA. Through non-disjunction in males of suitable stocks, fertile Compound(l) females which lack the Y chromosome, phenotypically distinguishable from their normal sibs, are produced in sufficient number to allow the subsequent breeding of X/O males in gram quantities for biochemical studies.
Extra cytoproct mutant inParamecium tetraurelia: a genetical study
Authors: Ng Stephen F. 
Published: September 2009

SUMMARYThe basis of inheritance of the extra cytoproct (XP) character inParamecium tetraurelia, stock d4-154, is shown to be nuclear and probably a single dominant gene,Ec, with reduced penetrance in heterozygotes. When the mutant gene is replaced by its wild-type allele, loss of the XP phenotype in some lines of descent occurs before 15 cell generations, but in more than half of the lines this occurs after 15–120 or more cell generations. The possibility is considered that these extremely long and variable ‘lags’ may be due to extranuclear (cortical) inheritance of cortical changes initially produced by gene action.
The genetics of mating type in the suctorianTokophrya lemnarum
Authors: Colgin-Bukovsan Laura Ann 
Published: September 2009

SUMMARYThe two clones produced by the two members of a conjugating pair are normally of the same mating type, about 50% of such synclones being mating type I, 50% type II. This ratio suggests (1) that mating type is determined by a pair of alleles at one locus or by a pair of mating type determining chromosomes, and (2) that one mating type is homozygous, the other heterozygous or hemizygous. Mating type ratios are unaffected by temperature or parental age. Exceptions are of three types: (1) mates that produce one clone of type I, the other of type II, (2) mates which fuse permanently and yield a clone pure for either mating I or mating type II, and (3) conjugation of three mates one of which is regularly non-viable, the two survivors producing either two clones of type I, two clones of type II or one of each type. The bases of these exceptional results remain obscure.
Position effect suppression of ribosomal RNA genes inDrosophila melanogaster: non-autonomous in gynandromorphs?
Authors: Pyati Jagdeesh 
Published: September 2009

SUMMARYBaker (1971) presented genetic evidence that the inviability ofIn(1)scL8/OandscS1/Omales in Drosophila melanogaster is due to position effect suppression of ribosomal RNA cistrons. AlthoughscL8/OandscS1/Omales are inviable,scL8/scL8andscS1/scS1females are viable. We therefore asked the following question: IsscL8/OorscS1/Oviable when part of a gynandromorph? In other words, is position effect suppression of rRNA genes autonomous or non-autonomous in gynandromorphs? In this paper preliminary evidence is presented which suggests that position effect suppression of rRNA cistrons is non-autonomous. The evidence is thatscLS/ orscS1/O(male) parts of gynandromorphs are not only viable but normal in appearance.
Electrophoretic identity of proteins in a finite population and genetic distance between taxa
Authors: Li Wen-Hsiung 
Published: September 2009

SUMMARYWehrhahn (1975) introduced the method of probability generating function to study the distribution of charge differences between homologous proteins in a population but considered only the special case where the population starts with a single allele. Some of his results, however, contained errors. In this paper, all the formulae are presented in general, correct yet much simpler forms. It is also shown that the method of diffusion equations (Ohta & Kimura, 1973) can produce the same results. Numerical computations show that the difference between the one-step and two-step models of charge changes is practically negligible. The results obtained have also been applied to study Nei's genetic distance. Numerical computations indicate that the genetic distance computed from electrophoretic data is about 10% smaller than the expected number of amino acid substitutions involving charge changes in the early stage of divergence of populations and may give a serious underestimate in comparisons between species.
Trimethoprim resistance controlled by a combination of plasmid and chromosomal genes
Authors: Amyes S. G. B. , Smith J. T. 
Published: September 2009

SUMMARYR388s is a mutant of the R factor, R388. Unlike its parent R388s does not confer trimethoprim resistance, though it does confer sulphonamide resistance and the ability to transfer. It is shown that when bacteria harbour R388s mutations to trimethoprim resistance occurred at a high frequency (3·5 × 10−4), whereas such mutations never occurred when the host lacked the R factor. Bacteria harbouring R388s did not mutate to resistance to any other antibiotics at a detectable frequency.The expression of trimethoprim resistance in bacteria possessing R388s appears to require two genes, one located on the R factor and the other situated presumably on the chromosome. The mechanism of trimethoprim resistance in these bacteria is probably due to reduced permeability and is thus quite unlike the insusceptible target site mechanism of the parent R factor, R388.
Effects of selection for independent changes in two highly correlated body weight traits of mice
Authors: McCarthy J. C. , Doolittle D. P. 
Published: September 2009

SUMMARYMice were selected for high and low body weight at 5 and at 10 weeks of age. Selection was performed (1) separately for each trait, and (2) for various combinations of the two traits, using (a) independent culling levels and (b) restricted indices. Two-way selection for each trait separately gave large responses and correlated responses. Selection by independent culling levels intended to increase 5-week weight while restricting change in 10-week weight gave no demonstrable response; selection by culling levels intended to decrease 5-week weight while restricting change in 10-week weight resulted in decreases in body weights at both ages. Index selection, intended to change weight at one age while holding that at the other age constant, was generally successful. Observed responses did not conform very well with predicted responses for either index or culling levels selection. The significance of these observations in regard to the problem of selection involving restriction of traits is discussed.
Experiments with themaroon-likemutation ofDrosophila melanogaster
Authors: Nissani Moti , Liu Chih-Ping 
Published: September 2009

SUMMARYCell lineage analysis of themaroon-likemutation ofDrosophila melanogasterrevealed the most extensive degree of non-autonomy reported to date inDrosophila: all 1454 gynandromorphs in whichXchromosome loss uncovered thema-lmutation hadma-l+.eye colour. In contrast, among 331 gynandromorphs in whichXchromosome loss simultaneously uncovered thevermilionandmaroon-likemutations, approximately 16% hadvphenotype but with one possible exception all gynandromorphs again hadma-l+eye colour. These results suggest that very small amounts of thema-l+gene product are necessary for wild-type eye colour development and they are therefore compatible with the one cistron–allelic complementation model that has been proposed for thema-llocus. They also provide the best estimate available to date ofIn(1)wvc-induced internal mosaicism: 7%. A preliminary attempt to detect DNA-induced transformants among 6 DNA-injected preblastodermma-lembryos and at least 80000 of their F1to F4descendants has yielded completely negative results. An investigation of the maternal effect whichma-l+mothers exert on the eye colour of their geneticallyma-loffspring revealed that, in contrast to earlier observations, this effect is not universal: some phenotypicallyma-land intermediatema-lflies were observed in young cultures. The discrepancy between this and earner observations is probably attributable to as yet uncharacterized nutritional deficiencies in the diet of flies used in this experiment. Cytoplasm drawn from blastodermma-l+embryos and injected into the posterior region ofma-lpreblastoderm embryos failed to induce eye-colour alterations in all seven flies which survived the treatment. Injection of the contents of embryos of certain genotypes and developmental stages intoma-lpupae 24–48 h old did alter in some instances the eye colour of treatedma-lflies. Various tests strongly suggest that these alterations are not due to injection of a substance that has been stored in the egg during oogensis or that has been produced by the embryo itself prior to injection and they therefore preclude the possibility that a simplein vivobioassay for thema-l+substance has been achieved. Rather, they indicate that the observed eye-colour alterations are due to transplantation of blastoderm-stage embryos which remain active long enough withinma-lhosts to produce and release a substance into the hosts' haemolymph and that this substance in turn induces phenotypic alterations in the hosts' eye colour. Whenvandma-leye colour changes are simultaneously monitored, it appears that injection of embryonic contents into pupae is equally or more effective in modifying thevphenotype than in modifying thema-lphenotype. Based on these observations, a tentative hypothesis regarding the time of activation of thema-l+gene and the relationship between the immediate product of this gene, the maternal substance stored in the egg and the substance released by tissue transplants is proposed.
Genetics and biochemistry of 5-Bromodeoxyuridine resistance inPhysarum polycephalum
Authors: Lunn Asgeir , Cooke David , Haugli Finn 
Published: September 2009

SUMMARY5-Bromodeoxyuridine (BrdU)-resistant mutants ofPhysarum polycephalumwere isolated as colonies of myxamoebae growing on BrdU-substituted bacteria after exposure to long-wave ultraviolet light (UV). Twenty-four such mutants were studied. They all show Mendelian segregation in crosses with wild type. Plasmodia constructed from mutant amoebae were all deficient in deoxythymidine incorporation. Extracts made from selected plasmodia showed that all except one had low thymidine kinase activity.Genetical and biochemical complementation studies revealed two complementation groups: 23 mutants,burA, had low thymidine kinase while 1 mutant,burB, had normal thymidine kinase levels.
Evidence that there are two types of determinant for tetracycline resistance among R-factors
Authors: Reeve E. C. R. 
Published: September 2009

SUMMARYA series of derepressed mutants of the tetracycline resistance (T) determinant in R-factor R57 have been found to be repressor-negative and recessive to the T determinant in R6. It is shown that these (Tdr) mutants are dominant to the inducible T determinant in RPl, indicating that the T determinants in R57 and RP1 code for different repressors of the resistance gene. The same Tdr determinants are unstable in cells carrying both the R57 mutant and RP1, probably due to selection against the dominant Tdr gene because it depresses the growth rate of the host cell compared with its T+homologue. It is suggested that the T determinants giving high-level resistance in R57, R6 and R100 form one homologous group, probably disseminated by the transposon TnlO, while T determinants giving a much lower level of resistance, such as that in RP1, form a separate group, which may include those in R46, and R199. It is proposed that the gene responsible for tetracycline resistance should be designatedtetAand the repressor genetetI. The R57 Tdr mutants then have the genotypetetI−tetA+.
Role of simple and complex aggregates inEscherichia coliHfr × F−matings
Authors: Broda Paul , Collins J. F. 
Published: September 2009

SUMMARYAnalysis of tetraparental Hfr × F−matings ofEscherichia colistrains showed that mating complexes were predominantly pairs or small aggregates of cells. Many physically associated complexes of donor and recipient cells gave rise to no recombinant cells. The observed linkage of genetic markers in recombinants is sensitive to multiple mating events, and should therefore be measured under well-defined conditions giving pairwise matings only.
The plasmid curing action of imipramine inEscherichia coliK12
Authors: Molnár J. , Béládi I. , Holland I. B. 
Published: September 2009

SUMMARYCuring of an F-prime plasmid by imipramine was most efficient on bacteria growing semianaerobically at 37 °C. The plasmid curing effect of imipramine was increased in the presence of methylene blue, whilst fluorescein, chlorpromazine-sulphoxide and tetraoxyanthrachinon antagonized the plasmid curing action of the drug. In addition to its plasmid curing effect, imipramine treatment selected for Lon mutants at high frequency. Lon mutants show increased resistance to the drug but cured strains, if Lon+, are not resistant.
Immunogenetics of a macroglobulin allotype in cattle
Authors: Iannelli Domenico , Masina Piero 
Published: September 2009

SUMMARYThe paper describes a cattle serum antigen (McA2) located on a macroglobulin molecule which has its isoelectric point at pH 5 and is capable of interacting with the wheat germ lectin and concanavalin A.The specificity is inherited in a simple Mendelian manner and the gene controlling its synthesis is allelic to the one controlling the synthesis of the McAl antigen.
The lactose system inKlebsiella aerogenesV9A: 6. Lactose transport
Authors: Wilson Dorothy M. , Wilson T. Hastings , Reeve E. C. R. 
Published: September 2009

SUMMARYKlebsiella aerogenesV9A carrying alacplasmid in addition to its chromosomal operon showed strongly positive fermentation of lactose on MacConkey lactose agar plates, and was found to transport the lactose analogue thiomethyl-β-galactoside (TMG) at a rapid rate. The strain that had been freed of the plasmid showed moderate transport due to the chromosomallacoperon. When a plasmid bearing a mutation inlac Ywas inserted into a strain with a normalYgene, the resulting diploid became lactose-negative in phenotype. The presence ofE. coliF′lacfactors that carriedlac Ymutations, whether deletions or missense or nonsense mutations, also renderedlac Y+Klebsiellalactose-negative. Such diploids, after growth in 1% lactose, transported TMG at a much lower rate than the corresponding plasmid-freelac Y+Klebsiella. However, this interference bylac Y−plasmids with the expression of the chromosomallac Ygene was not seen when cells were induced with IPTG or when the chromosomal and plasmidlacoperons were both constitutive. It was found that this effect of the plasmids was dependent on their possessing an intactlacZgene.
Recombinational analysis of the viablet-haplotypet38
Authors: Bennett Dorothea , Artzt Karen , Cookingham Janice , Calo Catherine 
Published: September 2009

SUMMARYA viablet-haplotype,t38, has been shown to distort linkage relations in theT−tfregion of mouse chromosome 17. Separate experiments were done with two different interstitial markers,Lowandqk, which map respectively about 5 and 4 centimorgans (cM) from the locus ofTin femaleT+tf/ + (Loworqk)+ heterozygotes. In females that carriedt38, however (i.e.t38+ + / +Low tfort38+ + / +qk tf), there was virtually no recombination betweent38and either interstitial marker, although thet38−tfdistance was normal. These observations suggest thatt38suppresses recombination in the lefthand part of that region and strongly enhances it further to the right.