bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decanalization of scutellar bristle number inDrosophila
Authors: Scowcroft W. R. , Latter B. D. H. 
Published: September 2009

SUMMARYA major difference in developmental stability has been demonstrated between two populations produced by artificial selection for supernumerary scutellar bristles. The test system involves the substitution of an X-ray induced partial revertant ofsc1for the wild-type allele at thescutelocus, enabling direct comparisons to be made of the degree of canalization at the wild-type level of expression of the character. One population is comparable with the unselected Canberra stock in stability, though it differs appreciably in mean bristle number: the other population shows a marked reduction in the level of regulation of bristle number variability. The alleles responsible for the reduced level of canalization are rare in the base population, and are of particular importance in the determination of limits to directional selection. Their effects on developmental stability have been shown to depend on the activity of the allele at thescutelocus.
Influence of the population genetic background on the persistency of a recessive lethal inDrosophila melanogaster
Authors: Ytterborn Karl H. 
Published: September 2009

SUMMARYIn a population of Drosophila melanogaster started from an inbred wild-type strain the recessive second chromosome lethal studied had shown overdominance which after many generations was lost. In the present study the persistence of this lethal was tested in three series each of five populations. The genetic backgrounds of the different series of populations were obtained from (a) the inbred strain, (b) the above original population after the overdominance had been lost, and (c) a population started from the same inbred strain and where another lethal had shown overdominance which subsequently had been lost. The lethal was overdominant in the (a) background but detrimental to the heterozygous carriers on the other backgrounds. The detrimental effect of the lethal was stronger in the (b) background than in the (c) background. The varying behaviour of the lethal is possibly due to different adapted background genotypes and/or different degrees of heterozygosity of the gene pools.
I-like resistance factors with thefi+character
Authors: Grindley June N. , Anderson E. S. 
Published: September 2009

SUMMARYThefi+(fertility inhibition+) property was originally described in R factors related to F (F-like factors). The originalfi−factors, in contrast, were related to the transfer factor of a colicin I factor (I-like factors). We describe here a group of R factors which arefi+but I-like. It is suggested that all the termsfi+,fi−, F-like and I-like be used in the description of transferable plasmids.
Transduction mechanisms of bacteriophage ε15II. Isolation of a bacteriophage related to ε15
Authors: Hedges R. W. 
Published: September 2009

SUMMARYA 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

SUMMARYIn 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

SUMMARYMutants 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

SUMMARYThe 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

SUMMARYThe 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

SUMMARYInKlebsiella 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

SUMMARYSerum 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

SUMMARYSpontaneous 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

SUMMARYDoublets 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

SUMMARYA 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

SUMMARYInitial 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

SUMMARYAn 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

SUMMARYInterspecific 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

SUMMARYMeasurement 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

SUMMARYA 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

SUMMARYThe 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 distribution of the fraction of the genome identical by descent in finite random mating populations
Authors: Stam P. 
Published: September 2009

SUMMARYThe 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

SUMMARYAfter 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

SUMMARYSaline 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

SUMMARYtsd1–1 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.
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

SUMMARYHaem 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.