bluuebunny/crossref_metadata_2025 huggingface dataset:
Transduction mechanisms of bacteriophage ε15II. Isolation of a bacteriophage related to ε15
Authors: Hedges R. W.
Published: September 2009

A bacteriophage was isolated from a strain ofSalmonella manilla. This phage, υ15, was found to have adsorption and conversion properties similar to phage ε15. The two phages show similar transduction efficiencies but phage υ15lysogenizes more efficiently. Phage υ15is not subject to repression by ε15type prophage. The densities of the two phages are indistinguishable.

Phage υ15can ‘cure’ ε15type prophages and recombination is possible between genomes of the two phages. It seems probable that they are heteroimmune representatives of a single bacteriophage family.
Utilization and interconversions of purine derivatives in the fission yeastSchizosaccharomyces pombe
Authors: Pourquié J. , Heslot H.
Published: September 2009

In the fission yeastSchizosaccharomyces pombe, growth responses of mutants strains in the de novo purine synthesis pathway, in the purine interconversion system, and of various double mutants, have been studied upon different purine-supplemented media. The results show that exogenous purine utilization as nucleotide source is based exclusively upon pyrophosphorylation of purine bases, and they make it possible to identify most of the enzymic steps acting, in this organism, upon a purine ring to give another purine ring.

A scheme of the interconversion system inSchizosaccharomyces pombeis given.
Pleiotropy ofp-fluorophenylalanine-resistant and antibiotic hypersensitive mutants ofPseudomonas aeruginosa
Authors: Dunn N. W. , Holloway B. W.
Published: September 2009

Mutants ofPseudomonas aeruginosaisolated as being resistant top-fluorophenylalanine (FPA-r) are pleiotropic, showing patterns of phenotypic alteration of host-controlled modification, growth rate at 37 and 43 °C, ability to grow on minimal medium, response to antibiotics and ribosomal characteristics. Alterations in host-controlled modification are also found in FPA-r mutants ofEscherichia coliB.

The pleiotropy arising in these FPA-r mutants ofP. aeruginosaappears to result from alterations in the specificity of protein synthesis. Phenotypic variations in host-controlled modification of the type found in the FPA-r mutants may provide a method for the detection of suppressor mutations which act by miscoding.
Quantitative genetic analysis in Phalaris tuberosa III. Maternal effects on seedling growth and development
Authors: Latter B. D. H.
Published: September 2009

The genetic basis of variation in rate of seedling growth, and development has been examined in the Australian commercial population of Phalaris tuberosa. A model of additive genetic maternal effects has been used, with seed weight of the female parent as an index of maternal ability. Rate of leaf appearance, rate of tillering and growth per tiller are all genetically variable in the population, with estimated heritabilities of 0·36, 0·23 and 0·34 respectively on an individual seedling basis. Total seedling growth has a lower heritability (0·17), due to a negative genetic correlation between tiller production and growth per tiller ( − 0·46). These two components have also been shown to be subject to qualitatively different seed size maternal effects. Genetic differences in seed size in the female parent have been found to influence growth per tiller, while environmental differences in seed size affect primarily the rates of leaf appearance and tiller production.
Genetic and environmental control of a continuous trait,Abnormal abdomen, inDrosophila melanogaster
Authors: Hillman Ralph
Published: September 2009

The mutant phenotypeAbnormal abdomenis under the control of a major gene,A53glocated distally on theXchromosome. The phenotypic abnormalities are a result of the developmental interaction between this major gene and a modifier system associated with the residual genotype. The primary developmental effect of this mutant genotype is an interference with adult histoblast differentiation resulting in a raggedness or loss of tergite material due to the changes in the formation of the adult abdominal hypoderm. A secondary effect is an interference with middorsal fusion of the histoblasts.

The developmental effect of the genotype is influenced by a number of factors which include crowding, humidity, temperature, and the age of the culture. The mutant phenotype is due to an interaction of the major gene and the modifier system in association with these environmental factors. Gene action in relation to the final phenotype is postulated to be a two-step affair. The first is an increase in protein synthesis under the influence of the modifier system; and the second is the reaction of the histoblast, under the influence of the major gene, to this increase in protein synthesis during its differentiation into adult hypoderm. The function of the environment in this sequence of developmental reactions is postulated to be in its control of the utilization of the increased protein associated with the action of the enhancer genes. This hypothesis is discussed in terms of (1) the production and utilization of gene products and of (2) the regulation of development in terms of this production and utilization in a balanced developmental system.
The lactose system inKlebsiella aerogenesV9A: 3. Specific repression of thelacoperon by melibiose and raffinose
Authors: Reeve E. C. R.
Published: September 2009

InKlebsiella aerogenesstrain V9A melibiose and raffinose fail to induce thelacoperon and strongly repress its induction by isopropyl-β-d-thiogalactopyranoside (IPTG). This repression is specific to thelacsystem and is not released by cAMP, which releases the catabolite repression exerted by glucose and sucrose. It is concluded that melibiose and raffinose bind to thelacrepressor molecule inKlebsiellaV9A, competitively displacing IPTG, and that the resulting complex is able to repress thelacoperon. OtherKlebsiellastrains tested show the same repression phenomenon.
Major urinary protein and immunoglobulin allotypes of recombinant inbred mouse strains
Authors: Potter M. , Finlayson J. S. , Bailey D. W. , Mushinski E. B. , Reamer B. L. , Walters J. L.
Published: September 2009

Serum and urine samples from seven recombinant inbred mouse strains, derived from a cross between BALB/c and C57BL/6, were examined to determine the immunoglobulin heavy chain (IgCH) and the major urinary protein (MUP) allotypes. CXBG and CXBJ exhibited the same IgCH alleles as did BALB/c; the others resembled C57BL/6, thus providing no evidence of crossover types. Comparison of the Mup and brown coat colour (b) alleles (both on linkage group VIII) revealed that three of the strains resemble BALB/c and two resemble C57BL/6, whereas the CXBE and CXBI strains are crossover types.
Meiotic reversion in an unstable strain of yeast
Authors: James A. P.
Published: September 2009

Spontaneous reversions from instability to stability were studied in a mutant homothallic strain of yeast. The mutant strain was characterized by persistent lethal sectoring attributable to the presence of a recessive locusuns1. It was found that (1) the meiotic reversion rate is about 140 times higher than the mitotic reversion rate, (2) reversions are much more common in the homozygoteuns1 uns1than in the heterozygoteUNS1 unsl, (3) revertant segregants and lethal segregants tend to occur together, and (4) meiotic revertants tend to occur as twin revertants. These results indicate that reversion from unstable to stable results from genetic recombination and that, in meiosis, this recombination involves an unequal exchange at the first division.
An analysis of the determinative difference between singlets and doublets of Oxytricha fallax
Authors: Grimes Gary W.
Published: September 2009

Doublets of Oxytricha fallax possess two complete sets of ciliature. The doublet phenotype is inherited through sexual and asexual reproduction as a cortically determined trait. The trait is also inherited through cystment, independent of cyst size. Prior work shows an absence of all visible cortical organelles, except cell membranes, in the cyst; thus the visible structures are not themselves determinative.

Results from excision experiments performed on encysting doublets indicate that the determinative difference between doublets and singlets is the presence of one or two ‘determinative regions’ located on the ventral surfaces of the organisms which serve as sites for the initiation of ciliary primordium development. Doublets possess two such areas, but singlets possess only one.
Inheritance of plasmodial valine requirement inPhysarum polycephalum
Authors: Dee Jennifer , Wheals A. E. , Holt C. E.
Published: September 2009

A defined medium forPhysarum polycephalumplasmodia has been devised containing glutamic acid, glycine, methionine, biotin, thiamine, glucose, salts and haematin, which supports good growth on agar plates of many different strains. Tests on this medium have revealed a requirement for valine in some plasmodia formed by homothallic progeny (mthapt-l+) from the crossa(mt1apt-l+) ×APT1(mthapt-l−). The valine requirement was also inherited among heterothallic progeny of this cross and its segregation was followed in several heterothallic crosses. To explain the results it is proposed that valine synthesis requires the presence of dominant alleles at either of two unlinked loci and that only plasmodia homozygous for recessive alleles at both loci are valine dependent. In some crosses studied only one pair of alleles is segregating and valine requirement thus provides a useful genetic marker, and the first reported nutritional marker inP. polycephalum. The value of crosses withapt−mutants for both the detection and analysis of plasmodial markers is demonstrated and discussed.
Infectious transfer of a fertility factor inStreptomyces coelicolor
Authors: Puglia A. Maria , Spada-Sermonti Isabella , Basile Santina , Misuraca Fara , Sermonti G.
Published: September 2009

Initial Fertility (IF) strains ofStreptomyces coelicolorare able to convert recipient strains (UF) to the IF condition by contact, without concomitant transfer of chromosomal markers. The conversion is prevented by the presence of acridine orange in the medium of the mixed culture. Acridine orange is also moderately effective in inducing the formation of UF variants from IF-treated strains. No effect of the drug is observed on UF variant formation from Normal Fertility (NF) strains nor on the behaviour of the fertility factor in NF × UF mixed cultures. The hypothesis is put forward that the fertility factor works as an episome inS. coelicolor, fixed to the chromosome in the NF strains, free in the IF strains and missing in the UF strains.
Selection of new inversions in multi-locus genetic systems
Authors: Charlesworth Brian , Charlesworth Deborah
Published: September 2009

An approximate expression, is derived for the rate of change in frequency of an inversion introduced at a low initial frequency into a multi-locus system at equilibrium under recombination and selection. It is shown that this expression gives accurate predictions of the rate of progress of the inversion, even if the initial population is perturbed somewhat from equilibrium. Extensions to the cases where there are sex differences in recombination and selection are considered. An implication of the results is that selection pressure for newly arisen inversions depends on the existence of a stable equilibrium with linkage disequilibrium. The expected chance of survival of a new inversion in a large population is shown to be approximately one half the square root of the loss in fitness due to recombination.
Interspecific aneuploidy inCucurbita
Authors: Bemis W. P.
Published: September 2009

Interspecific aneuploids were made in the genusCucurbitaby pollinating the autoallotroploid (diploidC. moschata– haploidC. palmata) with pollen from diploidC. moschata. Seventy-eight, or 0·36%, of the potential ovules showed some degree of continued development after pollination. The high frequency of continued ovule and embryo development indicated a preferential distribution or loss ofC. palmataunivalents during meiosis in the autoallotriploid and that megagametes aneuploid for more than oneC. palmatachromosome were capable of initiating continued ovule development after fertilization. Lethal effects of interspecific aneuploidy were expressed by complete embryo abortion to sterility of mature plants. Nine plants developed to maturity and seven were cytologically identified. Four were trisomic and two were monosomic for singleC. palmatachromosomes, i.e. they were 2n+ 1 and 2n+ 19 (n= 20) respectively. One plant was 2nand phenotypically identical to theC. moschataparent. One 2n+ 1 plant was fertile and the singleC. palmatachromosome was transferred in the succeeding generation.
Surface exclusion by ColV–K94
Authors: Willetts Neil , Maule John
Published: September 2009

Measurement of ColEl transfer by ColV2, inE. coliK12, showed that ColV2 specifies a surface exclusion system. This system is different from those specified by Flac, and by ColVBtrpand Rl-19. Like these other two systems, the ColV2 surface exclusion system is subject to inhibition by the appropriate transfer inhibitor, and is not expressed in stationary phase cells.
Population structure in artificial selection programmes: simulation studies
Authors: Madalena F. E. , Hill W. G.
Published: September 2009

A simulation study was undertaken of methods of subdividing populations into several small sublines and utilizing the variances generated between lines by selecting among them. Crosses of chosen lines were made, and either selection was continued in a single large population (single cycle) or the population was subdivided again (repeated cycles). As a control for the efficiency of these schemes, a single large population was maintained and selected at the same intensity from the outset. Simple models were used of additive or completely dominant genes, usually of equal effect and equally spaced on a single chromosome.

The single and repeated cycle structures give similar results, but the repeated cycle structure is more extreme.

With additive models intense selection between lines gives short-term advances, but causes a reduction in the limit when compared with a single population. The effect on the limit is greatest with free recombination, very small with complete linkage. If no selection is practised between lines the limit is unaffected, but takes longer to attain.

With complete dominance, and the recessive allele initially at low frequency, greater responses from selection are obtained within sublines than in the large population, large gains are made from selection between sublines, and a higher limit can be reached. If the recessive allele is at high initial frequency the subdivision is not beneficial.

Some simple theory is developed to explain these results. It is concluded that subdivision and crossing schemes are unlikely to be very useful except for elimination of deleterious recessive genes.
Genotype, protein, phenotype relationships in self-incompatibility of Brassica
Authors: Nasrallah M. E. , Wallace D. H. , Savo R. M.
Published: September 2009

The inheritance of self-incompatibility proteins was studied in three homozygous self-incompatible genotypes of Brassica oleracea var. capitata and their F1 and F2 progenies. The presence or absence in the stigma of incompatibility proteins was determined by immunodiffusion and independently by disk electrophoresis. Certain proteins (antigens) were present in F1 and F2 plants in exact correlation with segregation of the S alleles as determined by phenotypic expression of incompatibility. An S allele–protein–phenotype relationship was thus verified.
The chromosomal integration of a β-lactamase gene derived from the P-type R-factor RP1 inEscherichia coli
Authors: Richmond M. H. , Sykes R. B.
Published: September 2009

The R-factor RP1, which carried the markersamp neo tet, confers resistance to penicillins by specifying the synthesis of Type IIIa β-lactamase. It was detected initially in a strain ofPseudomonas aeruginosa(Sykes & Richmond, 1970) and fragments spontaneously inPs. aeruginosastrain Ps 18 to give clones which carry only theampmarker. Such clones are said to carry the element RP 1–1 since they are still capable of specifying the transfer of ampicillin and carbenicillin resistance to appropriate recipients in mating experiments. However, unlike lines carrying RP 1, they contain no detectable extrachromosomal DNA (Ingramet al.1972), and the likely supposition is that theampgene in these clones has become integrated into the bacterial chromosome together with the regions necessary to allow such strains to act asampgene donors in mating experiments. It is probably cells ofPs. aeruginosain which theampgene has become integrated together with an RTF region that are responsible for the transfer of chromosomal markers reported by Holloway & Stanisich (1971).
The distribution of the fraction of the genome identical by descent in finite random mating populations
Authors: Stam P.
Published: September 2009

The probability distribution of the heterogenic (non-identical by descent) fraction of the genome in a finite monoecious random mating population has been derived. It was assumed that in any generation the length of both heterogenic and homogenic segments are exponentially distributed. An explicit expression is given for the expected number of ‘external junctions’ (sites that mark the end of a heterogenic segment) per unit map length in any generation. The latter necessitates the introduction of two higher-order identity relations between three genes, and their recurrence relations. Theoretical results were compared with the outcome of a series of simulation runs (showing a very good fit), as well as with the results predicted by Fisher's ‘theory of junctions’. In contrast to Fisher's approach, which only applies when the average heterogeneity is relatively small, the present model applies to any generation.
The genetic implications of u.v. light exposure and liquid-holding post-treatment in the yeastSaccharomyces cerevisiae
Authors: James M.  , Parry Elizabeth M.
Published: September 2009

After liquid-holding treatment in saline, cultures of yeast exposed to u.v. light showed an increased resistance to a second exposure to u.v. irradiation. This increase in resistance during a second series of u.v. exposures was correlated with an increase in the induction of intragenic recombinants. In contrast, no increase in the frequency of the intergenic recombinants or mutations to prototrophy could be detected during the second u.v. dose range. The results obtained could not be explained by the induction of meiosis during liquid holding or by changes in the timing of cell division after u.v. exposure.

A model of u.v. repair in yeast is postulated in which liquid-holding treatment results in changes in the proportions of lesions repaired by excision repair and recombination repair (respectively).
Genetic analysis of physiological homeostasis: glomerular filtration rate following saline loading in mice
Authors: Stewart J. , Mowbray S.
Published: September 2009

Saline loading caused an increase in glomerular filtration rate in RAP mice but not in CBA mice. On the basis of progeny testing of F 2 hybrids, backcrosses to CBA, and inbred lines derived from backcrosses to RAP, it was concluded that the difference between the strains RAP and CBA was probably largely accounted for by a single gene locus. The use of this gene in physiological investigations of the control of glomerular filtration rate is suggested.
Recombination during blocked chromosome replication in temperature-sensitive strains ofUstilago maydis
Authors: Unrau P. , Holliday R.
Published: September 2009

tsd1–1 strains ofUstilago maydisare blocked in DNA synthesis under restrictive conditions. On recovery from the block, both intergenic and allelic recombination are enhanced, and aneuploids are generated. UV is synergistic in the induction of recombination. Direct assays of allelic recombination have shown that gene conversion occurs during the block in DNA synthesis.
Temperature-sensitive mutations inHabrobracon
Authors: Smith Roger H.
Published: September 2009

Techniques for isolating and analysing temperature-sensitive mutations inHabrobracon serinopaeare presented. The temperature-sensitive patterns and lethal phases are described for nine different mutant strains. Such mutants are well suited for the study of gene action during development.
Disturbed haem and globin synthesis in reticulocytes of prenatal flexed-tailed (f/f) anaemic mice
Authors: Cole R. J. , Garlick J. , Tarbutt R. G.
Published: September 2009

Haem synthetase activity and co-ordination of α- and β-globin chain synthesis have been investigated in prenatal reticulocytes of congenic FL/4Re +/+Lvb/Lvband FL/1 Ref/f Lvb/Lvb, mice, which have a marked hypochromic, microcytic, siderocytic anaemia, with reduced erythrocyte numbers at birth, and also in other stocks bearing theflesion. Haem synthetase activity inf/freticulocyte homogenates was similar to that in normal cells but was markedly dependent on protoporphyrin added to the homogenate, while activity in normal cell homogenates was relatively independent of added precursor. In cultured normal prenatal reticulocytes α- and β-globin was synthesized in approximately equal amounts during a 4 h labelling period, but inf/freticulocytes there was an approximate 50% deficiency in β-globin chain synthesis. This deficiency could be repaired by added haem but not by protoporphyrin. Such a lesion is quantitatively consistent with the observed hypochromia of neonatalf/ferythrocytes. The relationship of this abnormality to effects of theflocus on early erythropoietic precursor cells is discussed.
Plasmodium formation without change in nuclear DNA content inPhysarum polycephalum
Authors: Cooke D. J. , Dee Jennifer
Published: September 2009

The 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

Interallelie 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.
Failure of growth regulation of the lens epithelium in strains of fast-growing chicks
Authors: Clayton R. M.
Published: September 2009

Two strains of poultry selected for high growth-rate were found to have an anomalous lens morphology indicating a failure of the normal process of growth regulation. The implications for lens fibre differentiation are discussed, as are the implications for genetic selection for growth-rate.
The independence of germ-cell genotype from somatic influence in chimaeric mice
Authors: McLaren Anne
Published: September 2009

Mouse 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

Sorting 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

A 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

Eleven 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

A 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

DNA 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

In 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

The 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

The 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

Baker (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

Wehrhahn (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

R388s 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

Mice 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

Cell 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

5-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

A 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

Analysis 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

Curing 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

The 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

Klebsiella 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

A 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.
Gross karyotypic change and evolution in North American cyprinid fishes
Authors: Gold J. R. , Womac W. D. , Deal F. H. , Barlow J. A.
Published: September 2009

We have examined karyotypes of five species from five genera of cyprinid fishes endemic to the central and southeastern United States: Campostoma anomalum, Hybognathus hayi, Hybopsis aestivalis, Phenacobius mirabilis, and Pimephales vigilax. All five have a diploid chromosome number of 50. Variation in chromosome arm number among the five species is slight, and may be due to measurement error or technique difficulties. The karyotypes of 40 North American cyprinids are now known. All but five species have 50 (diploid) chromosomes. Variation in chromosome arm number also appears minimal; one-armed chromosomes (centromeres subterminal to terminal) normally comprise only a small fraction of the karyotype, and each species has roughly the same number of chromosomes with median and submedian centromeres. The conservatism of gross chromosomal evolution among these fishes is not in accord with recent hypotheses which suggest that progressive evolution of organisms may depend to a large degree on gene rearrangement brought about by gross chromosomal restructuring. Cyprinids are a highly speciose group in North America, and there is relatively strong morphological differentiation among species. The present data suggest that gross chromosomal restructuring may play only a minor role in the speciation and evolution of these fishes.
Allozyme polymorphism in the parasitic hymenopteraDiadromus pulchellusWSM. (Ichneumonidae)
Authors: Shaumar Nagat , Rojas-Rousse Danielle , Pasteur Nicole
Published: September 2009

The allozyme polymorphism ofDiadromus pulchellushas been analysed at 22 loci, the expression of one (Est-4) being male-limited. Six loci were found polymorphic for two (Ldh-1,Ldh-2,Acp-2,PgiandSdh) or three (Est-3) codominant alleles. Allele frequencies are similar in males and females at four loci in a laboratory population but there are important heterozygote deficiencies in females at three of them. The possibilities of negative heterosis or assortative mating to explain this deficiency are discussed.