bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic analysis of actidione resistance inSaccharomyces cerevisiae
Authors: Wilkie D. , Lee B. K. 
Published: September 2009

1. Individual genes of a multigenic system of resistance to actidione in yeast were analysed in a series of crosses involving resistant strains and sensitive strains.2. Resistance conferred varied in the range 0·5 p.p.m. to 20 p.p.m.3. Positive interaction was seen between resistance genes in recombinant strains.4. Recessive modifier genes were found which do not themselves confer resistance but which modify the activity of specific resistance genes in a positive way, that is towards a greater degree of resistance. Both a two-fold and a five-fold increase in resistance is seen depending on the gene combination.5. In selection experiments, strains resistant to relatively high concentrations of actidione (1000 p.p.m.) were obtained but only by selection on media containing successively higher concentrations of the drug, that is, by the step wise build up of multiply mutant forms. Mutations of interacting resistance genes and specific modifier genes were obtained by selection methods including pretreatment of cells with ultra-violet light.
The production and behaviour of diploids ofCoprinus lagopus
Authors: Casselton Lorna A. 
Published: September 2009

Diploid strains ofCoprinus lagopushave been synthesized from commonAheterokaryons either as oidial colonies or sectors. The criteria of growth rate and colony morphology on selective medium were used to distinguish between diploid and heterokaryon colonies. The average oidial size and hyphal width of diploid strains was significantly greater than that of the haploid parental strains.Diploid monokaryons were very stable and only rarely produced haploid segregants. However, aneuploid intermediates in haploidization have been identified and these segregated further to give haploid monokaryons with recombinant genomes.Dikaryons formed from diploid and haploid strains produced fruiting bodies. Meiosis and basidiospore production were irregular owing to the formation of triploid or partially triploid fusion nuclei in the basidia. In contrast to their stability in monokaryons, diploid nuclei tended to be unstable when combined in a dikaryon with a haploid nucleus, and often underwent partial haploidization before fruiting. Segregation of genes in the basidiospore progeny reflected whether haploidization had occurred before or after the formation of the fruiting body. If the haploid nucleus had aBmating-type allele common to the diploid nucleus, haploidization effected loss of the common allele.
New data on the linkage map ofStreptomyces coelicolor
Authors: Hopwood David A. 
Published: September 2009

Linkage data, obtained by a combination of selective analysis of haploid recombinants and analysis of segregating heterozygotes, are given for twenty-eight loci inStreptomyces coelicolorA3(2). This brings the total known loci for the organism to thirty-nine. The two linkage groups previously recognized remain separate, and their lengths have been increased to about 60 and 70 recombination units respectively. Whether the two linkage groups correspond to two chromosomes remains an open question.Three further examples of close linkage of pairs of functionally related loci have been found (a trio of such loci was already known), and three other pairs provide possible examples of the same phenomenon. Some loci which are clustered inSalmonellaare unlinked inStreptomyces.
Inherited histocompatibility changes in progeny of irradiated and unirradiated inbred mice
Authors: Bailey D. W. , Kohn H. I. 
Published: September 2009

(1) F1-hybrid mice derived from a cross of the highly inbred strains: C57BL/6 and BALB/c, were tested for inherited changes of histocompatibility by an orthotopic inter-exchange of tail-skin grafts. The fathers of tested mice received either 522 rads of gonadal X-irradiation, or received no irradiation 2 months prior to mating.(2) Thirty-two mice with altered histocompatibilities were found in a total of 2572 complete tests. All of those mutant mice (twenty-one) that produced an adequate number of offspring were shown to pass the incompatibility on to their progeny.(3) Mutants were classified as to whether they effected a gain, a loss or both a gain and a loss in antigen specificity as determined by whether they rejected skin of donor mice or their skin was rejected by host mice. Twenty-six were clearly of the gain type, five were most likely gain type and only one showed both a loss and a gain effect. There was no clearcut evidence that loss types had occurred. The preponderance of gain types was tentatively explained as an artifact of the system used for the assay.(4) Several of the detected mutants were probably from parents carrying mutations that originated in past generations, for some mutant mice occurred in clusters.(5) There was no apparent effect of paternal irradiation (522 rads) on mutation frequency. The induced mutation rate was estimated to be less than 2·6 × 10−5/ gamete/rad.(6) Independent data on isografts from F1hybrids of proven non-carrier pedigreed parents provided an estimate of spontaneous mutation rate of 6·75 × 10−3/ gamete.(7) The estimate of doubling dose (greater than 260 rads) was consistent with the estimates for recessive lethals and visibles in mice.
Quantitative genetic analysis in Phalaris tuberosa II. Assortative mating and maternal effects in the inheritance of date of ear emergence, seed weight and seedling growth rate
Authors: Latter B. D. H. 
Published: September 2009

The variation shown by the Australian Commercial population of P. tuberosa in respect of date of ear emergence, seed weight and seedling weight has been analysed, and the interrelationships among the variables characterized. All three characters show appreciable additive genetic variation, in the sense that approximately seven generations of artificial selection would be sufficient to push the population mean for each trait beyond the range shown by introduced ecotypes.Apart from the positive association between seed weight and seedling weight due to maternal influence, the three variables are to a large extent genetically independent in this locally adapted interbreeding population. It is therefore probable that the negative ecotypic correlations between seedling growth rate and date of ear emergence, and between seed weight and date of ear emergence, would rapidly be dispelled under random mating in a synthetic population.Under open-pollination, date of ear emergence has been shown to be subject to phenotypic assortative mating of degree ρ = 0·78, approximately 53% of the variation being additive genetic. Variation in seed weight within the strain is extensive, with a heritability of 0·79. Neither character shows evidence of important genotype × years interaction.Variation in seedling weight involves an appreciable genotype × environment interaction component, and has a heritability of only 0·17 which includes variation due to genetically determined maternal effects. The correlation between the seed weight of an ovule parent and the ‘ true’ mean seedling weight of the derived maternal half-sib group is of the order of 0·57. It has been estimated that the correlated response per generation in seedling weight, due to selection for seed weight, is 0·54 times that expected from direct selection.
Effects on genetic recombination ofEscherichia coliK 12 produced by P32decay in the Hfr male
Authors: Krisch Robert 
Published: September 2009

The effects of P32disintegration in the Hfr donor cell on the genetic recombination ofEscherichia coliK 12 have been studied. The dose-response relationship for the transfer of markers at a distancexfrom the chromosomal origin,N/N0=e−αxD, which summarizes the findings of Fuerstet al.(1956) for early markers of Hfr H, has been found to hold true to a good approximation for more distal selected markers in this strain, as well as for selected markers of Hfr CS, which transfers its chromosome in the opposite direction. The inheritance by recombinants of non-selected male markers located between the origin and the selected marker is not affected at all by prior P32dose to the Hfr. The sensitivity of each Hfr strain studied to the lethal effects of P32decay corresponds to the sensitivity to transfer effects of a male marker located about one-third of the total chromosomal length away from the origin. Genetic and lethal effects in Hfr H showed the same dependence on storage temperature during P32decay. Our data, therefore, supports the concept of a common origin for the lethal and genetic effects of P32decay.The quantitative predictions of current models for chromosome transfer with regard to radiation mating experiments have been examined. A simple model, involving no DNA synthesis, as well as the replicon model of Jacobet al.(1963) predict exponential marker inactivation curves of the kind found experimentally. The model of Bouck & Adelberg (1963) predicts a more complex dose dependence, but one not nearly so different from that of the other two models as was anticipated by Jacobet al.It appears unjustified to attempt to exclude any of the three models on the basis of presently available data from radiation mating experiments.
The multiple electrophoretic bands of mouse haemoglobins
Authors: Morton J. R. 
Published: September 2009

A survey of past work shows that certainty in the electrophoretic classification of mouse haemoglobins requires further understanding of the meaning of the multiple electrophoretic bands observed.Six electrophoretic bands are observed in all. Numbered in order of mobility they give the formulae 2 for Hb-s, 1235 for Hb-d, 1246 for Hb-p and 12345 for foetal haemoglobin (Hb-f). When mercaptoethanol is added to the electrophoretic medium these formulae become: 2 for Hb-s, 23 for Hb-d, 24 for Hb-p, 234 for Hb-f. Bands 5 and 6 and a fast ultra-centrifuge fraction both increase when samples are stored.Bands 5 of Hb-d, 6 of Hb-p, and probably 5 of Hb-f, are dimers of the whole haemoglobin molecule almost certainly joined by sulphur bridges. The monomers are bands 2 and 3 of Hb-d and 2 and 4 of Hb-p. Within each type interconversion of bands 2 and 3 and bands 2 and 4 has been observed.The hypothesis is suggested that Hb-d and Hb-p both exist as two conformational isomers. In each case one isomer is electrophoretically indistinguishable from Hb-s: the other permits the electrophoretic recognition of their differences in bands 3 and 4, and the formation of sulphur bridges to give bands 5 and 6.
Variability and restrictions against inbreeding and unequal family size in control populations ofTribolium
Authors: Bray D. F. 
Published: September 2009

Data from three experiments bearing on the relative stability of the four mating systems required to test the restrictions against inbreeding and unequal family size were examined in relation to the results given by Robinson & Bray (1965).Tribolium castaneumwas the experimental animal used in these experiments.An analysis of variance indicated that both restrictions were probably effective (Papproximately 0·10) in reducing the phenotypic variability of control population means. It seems likely that the apparent gain in stability obtained when the inbreeding restriction was used in addition to the restriction against unequal numbers is due to non-random genotypic proportions which would affect estimates of genetic variability based on assumptions of random mating.
The interaction between effective population size and linkage intensity under artificial selection
Authors: Latter B. D. H. 
Published: September 2009

The effects of tight linkage on the total response due to pairs of identical additive loci, segregating in a population initially in linkage equilibrium, have been studied both algebraically and by means of computer simulation. Particular attention has been given to the effects of finite population size on the probabilities of (a) the elimination from the population of the gamete carrying both ‘plus’ alleles; (b) the joint preservation of the two types of repulsion gametes; (c) the recovery of the desired combination of plus alleles through crossing-over; and (d) the fixation of the gamete in the population following its recovery.The study is restricted to situations in which linkage is known to have an appreciable effect on total selection response, i.e. to the case of genes of large effect initially at low frequency. A comparison of regimes with the same expected response under free recombination has shown the probability of (a) to be high, and the probability of (b) to be very nearly the same for all regimes tested. Provided that the recovery of the gamete carrying both plus alleles is an unlikely event at any given point in time, the probability of the fixation of the gamete, once reconstituted, is expected to be independent of population size for genes of large effect. In this context, approximate algebraic expressions have been derived for the probability of effective recovery of the required gamete, and for the mean waiting time involved.
Genetic control of flagellar structure inChlamydomonas reinhardii
Authors: Warr J. R. , McVittie A. , Randall John , Hopkins J. M. 
Published: September 2009

Seventeen non-motile strains ofChlamydomonas reinhardiiisolated by Dr Lewin and thirty-six newly isolated strains have been examined in the electron microscope for structural abnormalities of the flagella. Fourteen of them have straight, paralysed flagella in which the central fibres are replaced by an irregular core of disorganized material. The fourteen mutations map at four unlinked loci. Some of them are leaky; light and electron microscope observations on leakiness are described. In the former case leakiness is measured by the proportion of motile cells, and in the latter by the proportion of intact centre fibres seen in transverse sections. The degree of leakiness is to some extent characteristic of particular loci.A partial suppressor of some of these mutations has been isolated which acts on all the mutant alleles at two loci and to a much lesser extent on four out of five alleles at a third locus.
Genetic control of the hydrolysis of aromatic esters by sheep plasma A-esterase
Authors: Lee R. M. 
Published: September 2009

1. The rate of hydrolysis by sheep plasma of some carboxylic and phosphate esters has been determined for a random flock, and for a flock previously selected for its ability to hydrolyse di-(2-chloroethyl) aryl phosphates.2. A discontinuous variation in hydrolysis rate was found with all substrates tested and, using combinations of substrates, six types of plasma could be distinguished, each type having a different pattern of esterase activity.3. The most useful substrates for distinguishing between phenotypes were 1-naphthyl acetate and 4-ethoxycarbonylcoumarin-7-yl acetate. Three rates of hydrolysis were possible for each of these esters, and the highest rate for one was invariably combined with the lowest rate for the other, although the converse did not apply.4. To explain these results, and those of Lee (1964), it has been postulated that the quantitative production of esterase hydrolysing 1-naphthyl acetate is governed by the presence of an allele, termed Esa, at a particular gene locus. Similarly, the production of esterase hydrolysing 4-ethoxycarbonylcoumarin-7-yl acetate is determined by allele Esb, and where neither substrate is attacked the presence of a third allele, Esc, is proposed.5. The hydrolysis rates of haloxon, 1-naphthyl butyrate and 4-nitrophenyl butyrate varied in the same way as that of 1-naphthyl acetate, whereas the hydrolysis of indophenyl acetate followed the same pattern as that of 4-ethoxycarbonylcoumarin-7-yl acetate. The variation in hydrolysis rate of Coroxon could be explained by assuming that Esa and Esb are equal in this respect.6. A mating experiment produced results which were in accordance with the genetic hypothesis, but were too few in number to provide confirmation.7. The genetic marking of six types of sheep is possible, utilizing the variation in plasma A-esterase activity.
Genetical and embryological studies of the jt form of syndactylism in the mouse
Authors: Center Elizabeth M. 
Published: September 2009

1. A form of syndactylism (jt) involving two or three digits on one or more feet has been found in the descendants of Swiss-albino mice treated with HN2. The fusions are in a proximo-distal direction and usually involve only the skin and soft tissues; digits 1 and 5 are unaffected.2. This type of syndactylism is apparently due to a single recessive gene, jt, whose penetrance is influenced by ‘genetic background’. Apparently the identical mutation has occurred independently in stock maintained at Bar Harbor and Stanford. Linkage tests indicate that jt is not linked with c or lu.3. Embryological studies of the developing footplate reveal a loss in both preaxial and postaxial footplate tissue, primarily the latter, prior to and during the condensation of mesenchyme into the precartilage of the digital elements in the jt/jt limb.4. The importance of the shape and amount of footplate tissue to the resultant morphology of the foot is apparent. It is evident that genes such as jt are responsible for changes in footplate development, but the immediate underlying factors which cause these alterations remain an unsolved problem.
A genetical study of thymineless mutants ofE. coliK12
Authors: Alikhanian S. I. , Iljina Tamilla S. , Kaliaeva Eza S. , Kameneva Svetlana V. , Sukhodolec V. V. 
Published: September 2009

The 150 independently isolatedthy−mutants ofE. coliK12 Hfr 3.OSO were studied genetically and phenotypically. Variants were found among the mutants in respect to the lag period of thymineless death, and temperature sensitivity. The latter correlates with mutations located at a specific site on the genetical map.Thethylocus is located between thecysandser/glygenes, and is a linear structure where 134thymutants are distributed over more than 17 sites. The site distribution of the mutants is not regular: about a half of them (62) are localized within one site and all these are temperature-sensitive.Two further genes involving utilization of thymine—tlrandtd—were found. Mutations oftlrlead to a reduced thymine requirement (0·5 μg./ml.instead of 20 μg./ml.). A mutation oftdresults in thymidine sensitivity.This latter character is expressed when thetd-sallele is transferred intoE. coliK12, prototrophic for thymine, by conjugation. Thymidine inhibition can be reversed by the addition of any riboside to the growth medium. Both genes map at the proximal end of the Hfr 3.OSO chromosome and are linked with thethrgene. The most probable gene order is:tlr-td-thr.The following results have been obtained from14C-thymine incorporation experiments with wild-type cells, as well as withthy−tlr+andthy−tlr−cells: (1) Wild-type cells incorporate exogenous thymine extremely poorly, but incorporate thymidine better. (2) Thethy−tlr+mutants are able to incorporate thymine only when high concentration are used, but can utilize a low concentration of thymidine. (3) Thethy−mutants are able to incorporate exogenous thymine as well as thymidine at low concentration. (4) Thetlrmutation is a thymine-specific one.
Evidence for polarity of chromosome replication in F−strains ofEscherichia coli
Authors: Donachie W. D. , Masters Millicent 
Published: September 2009

The inducibility of three enzymes (β-galactosidase, tryptophanase and D-serine deaminase) has been measured at various times during the cell cycles of three strains ofEscherichia coli(K12 58–161 F−, B/r F–and 15T−). In each strain sharp increases in inducibility of these enzymes occurred at characteristic periods in each cell cycle. Such increases depend on DNA replication and therefore probably reflect synchronized gene replication. It is inferred that chromosome replication in these F−strains is sequential from a fixed origin.Infection with F′Lack+results in an extra period of increase in inducibiity of β-galactosidase in each cell cycle. It is concluded that the F′ episome replicates once in each cell cycle at a time soon after cell separation.
The ecological genetics of growth in Drosophila 8. Adaptation to a New Diet
Authors: Robertson Forbes W. 
Published: September 2009

1. Populations of Drosophila melanogaster have been adapted to a new, initially unfavourable diet by adding to the food medium the chelating agent, EDTA, which lowers survival, lengthens development and reduces body size, according to the concentration.2. Six populations were allowed to adapt to the new diet without intervention and compared with two additional populations in which there was either artificial selection for fast development time or in which the effects of variation in development time were minimized and higher egg production was favoured instead.3. All populations adapted successfully and some were able to grow on medium with EDTA concentrations which were lethal for the original population.4. Under uncrowded conditions on EDTA-free medium, in seven out of the eight populations, body size was reduced by about 7% below the level of the original population and the larval period was shorter in several instances. But in the population in which higher egg production was favoured, body size was 7% greater than in the original population and 16% greater than the average of the other EDTA-adapted populations. This contrast was attributed either to intense natural selection for shorter development time or to selection for a higher rate of egg production, which is positively correlated with body size when larvae are grown on sub-optimal conditions.5. Under crowded, competitive conditions, the fitness of the EDTA-adapted and the original populations was reversed according to the presence or absence of EDTA.6. Genetic differences between one of the EDTA-adapted populations and the original population were studied by using marked inversions to interchange chromosome pairs. Larvae of the alternative genotypes were grown on different diets and adaptation was shown to have involved changes in all major chromosomes and also substantial, complementary interaction between non-homologous pairs. Substitution of the third pair of chromosomes from the original Pacific stock in the background of the adapted strain led to complete sterility of females, on all diets tested, and lethality of both sexes at higher levels of EDTA.7. The creation of new equilibria, by manipulating the relative importance of components of fitness, in the course of adaptation to a new environment, offers a valuable technique for studying the selective forces which influence the mean value of quantitative characters generally.
‘Nude’, a new hairless gene with pleiotropic effects in the mouse
Authors: Flanagan S. P. 
Published: September 2009

1. Nude is a new recessive gene causing hairlessness in the mouse. It is linked to rex and trembler in linkage group VII. The order of the three loci and the recombination frequencies are as follows:2. In addition to hairlessness the new gene causes reduced body growth rate, very low fertility and a liver disease causing death. Nude mice may be classified at birth by the absence of vibrissae.3. The hairlessness is due to abnormal keratinization of hair in the follicles. The skin histology resembles that of naked mice. The hair follicles were found to be deficient in free sulphydryl groups.4. The majority of nude mice die of general body weakness within 2 weeks of birth. The survivors grow slowly and may live for a considerable period. But all nude mice eventually die, usually between 3 and 14 weeks of age.5. The livers of dead or moribund nude mice are covered with lesions and scars. The defect has been traced histologically to its initial stage, namely, necrosis of small areas of tissue.6. Attempts to relate the deficiency of sulphydryl groups in the hair follicles to abnormal sulphur metabolism in the liver were unsuccessful.7. Pseudo-cysts of a parasitic protozoan,Toxoplasma gondii, were identified in the liver and brain of nude mice. In one case the free form of the organism was found.8. The possible relationship between the liver disease and the pathogenic organism is discussed.