bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanism whereby the genesM1andM2inParamecium aurelia, stock 540, control growth of the mate-killer (mu) particles
Authors: Gibson I. , Beale G. H. , Reeve E. C. R 
Published: September 2009

1. Replacement of the dominant genesM1andM2inParamecium aurelia, stock 540 (syngen/variety 1), results in loss of ability to maintain mu particles and manifestation of mate-killing after a delay of eight to fifteen fissions in most cells. The change, when it does occur, is relatively abrupt, extending over less than the space of one inter-fission period.2. The delay between change of genotype and loss of mu particles is interpreted as being due to presence in the initial cytoplasm of some thousand ‘metagons’, which are non-replicating gene derivatives having the physiological activity of the corresponding genes. During successive fissions of paramecia deprived ofM1andM2the metagons are passively distributed amongst the progeny, until virtually all animals lack them.3. On reaching a stage at which some individuals of genotypem1m1m2m2contain only a single metagon, the paramecia still contain large numbers of mu particles and are mate-killers. Fission of such animals gives rise to one daughter again with mu particles, and another in which the latter are destroyed during the next inter-fission period.4. By induced cytoplasmic exchange between conjugants, metagons can be transferred from one animal to another via the cytoplasm. Where such transference is into an animal not originally containing mu particles, that animal is converted into a condition in which it favours the maintenance of mu particles and transmits the latter to one or more of its offspring.5. Distribution of metagons amongst progeny of dividing paramecia is not random, due possibly to clumping of the metagons. Induced cytoplasmic exchange seems to break up the clumps.6. Reintroduction of a dominant gene (M2) into a cell recently deprived of the same gene, succeeds—even after fifteen fissions—in re-establishing the ability to support growth of mu particles, provided that the recipient cell contains at least one metagon and one or more mu particles. There is a regular lag of only one fission between introduction of such a dominant gene and its phenotypic manifestation.7. Mathematical formulae are developed for calculating the expected initial number of metagons, the proportions of animals lacking mu particles at each fission following loss of the dominant genes, and the proportions of cells containing 0, 1, 2 …, etc. metagons per cell at any stage. The consequences of one of the possible types of irregular distribution of metagons in dividing paramecia are also considered mathematically.
Selection for rate of larval development usingDrosophila melanogastercultured axenically on deficient diets
Authors: Sang James H. 
Published: September 2009

1. The problem of improving rate of larval development ofDrosophilaby selecting for this ‘character’ on deficient diets is examined by culturing larvae axenically on low-casein and low-pyridoxine media. Under these conditions it is possible to develop strains which grow faster than the parent population.2. Selection for fast- and slow-growing larvae on a low-pyridoxine diet proceeds with a realized heritability of about 20%, but progress ceases after eight to nine generations. The selected larvae show no alteration of pyridoxine requirements up to the tenth generation, but the lines develop at different rates under optimal conditions. This difference is exaggerated when the diets are low in pyridoxine. By the fourteenth generation, requirements of the two lines for optimal growth have become distinct, the fast line requiring less pyridoxine than the control. Casein requirements show about the same optimum for the two lines but this is lower than that of the control, foundation population.3. Selection for fast- and slow-development lines on a low-casein diet continues to be effective throughout the fifteen generations of the test. The realized heritability in this case is about 10%. The optimal requirements of the two lines are the same, and there is little difference in their development rates when reared on this optimal diet. The response is found only under sub-optimal conditions, both of deficiency and of excess casein. Pyridoxine requirements do not seem to be altered in the two lines.4. Crosses between the selected lines show that each genotype has its own optimal environment, as judged by pyridoxine and casein requirements. Crosses among the lines after fourteen generations show that all the hybrids are superior to the mid-parent and three grew faster than the better parent. Other environments would have given different results.
The effects of inbreeding and artificial selection on reproductive fitness
Authors: Latter B. D. H. , Robertson Alan 
Published: September 2009

The competitive-index method of measurement of over all fitness inDrosophilahas been used to measure the effect of inbreeding and of artificial selection for metric characters in a large population ofDrosophila melanogaster. The technique itself was examined in detail with particular reference to its repeatability and to the effect on it of the modification of various environmental variables.With continued full-sib mating the decline in the competitive index was very rapid (it was reduced to a half by a single generation of full-sib mating) and there were no indications that interactions between deleterious genes at different loci were important in determining the rate of decline of fitness as inbreeding increased. Other unselected lines with ten pairs of parents in each generation were carried to serve as a control for the lines under artificial selection. At the same theoretical degree of inbreeding the control lines had a much higher average fitness than the lines produced by continued full-sib mating.From the base population lines were selected in both directions for abdominal bristles, sternopleural bristles and for wing length, there being two replicates in all cases. Four control lines were kept with the same number of parents as the selected lines. In all cases the selected lines declined in fitness below the value for the base population. However, in three of the lines the fitness was not significantly below the value for the control lines. The effect of artificial selection on fitness was asymmetrical, the decline being greater with down selection for all characters.The relevance of these results to various theoretical models is discussed. If the variation in these characters is actively maintained in the base population by the selection of heterozygotes then the results are consistent with an average selection disadvantage of homozygotes relative to heterozygotes of about 0·5%.
Genetical studies on the skeleton of the mouse XXXI. The Muscular Anatomy of Syndactylism and Oligosyndactylism
Authors: Kadam K. M. 
Published: September 2009

1. Changes in muscles and tendons in sm/sm are confined to hands and feet. They are closely correlated with the changes in the osseous skeleton.2. In Os/+, muscular changes are much more complex and not confined to hands and feet, but include the muscles of the forearms and of the lower legs. Some of the muscular changes, especially on the postaxial side, are not correlated with the changes in the osseous skeleton.
The effects of stabilizing selection on the time of development in Drosophila melanogaster
Authors: Prout Timothy 
Published: September 2009

The length of time of development, from oviposition to emergence in Drosophila melanogaster was subjected to stabilizing selection. In each generation only the individuals emerging close to the mean development time were used as parents of the next generation. This line was designated the ‘S’ line. In a parallel line disruptive selection was practised; where in each generation the earliest flies to emerge were mated to the flies last to emerge; those emerging at intermediate times were discarded. This line was designated the ‘D’ line. Two control lines were also carried, where the flies were mated at random with respect to time of emergence. The experiment extended for 40 generations and produced the following results:(1) The variance of development time decreased in the S line and increased in the D line, relative to the control lines.(2) The mean development time decreased in the S line and increased in the D line.(3) The coefficients of variation decreased in the S line and increased in the D line.(4) The viability, measured as per cent flies emerging, decreased in the D line.Toward the end of the experiment the amount of additive genetic variance in the selected lines and in the control lines was estimated from the response to directional selection. The estimates showed that (i) the loss of total variance in the S line can be accounted for completely by a loss in additive genetic variance, and (ii) the increase in the total variance of the D line cannot be ascribed to an increase in the additive genetic variance. It was probably due to an increase in the environmental component of variance, i.e. to a loss of ‘buffering capacity’.
The production of visible mutations inDrosophilaby chloroethyl methanesulphonate (CB 1506)
Authors: Auerbach C. 
Published: September 2009

The claim that CB 1506 produces an unusually high proportion of visible to lethal mutations could not be confirmed. The ratio of visible to lethal sex-linked mutations was less than 1:10 in bothMuller-5and attached-X tests. In one brood it rose to 1:5 when unconfirmed visible mutants were included. The much higher ratio obtained by Fahmy and Fahmy is interpreted as a methodological artifact, due to the inclusion in their calculations of mosaic visibles but not of mosaic lethals.Two visible mutations—twisted abdomen andwsatsuma—occurred more than once. This suggests the possibility of a locus or allele specific effect of CB 1506.
The action of ribonuclease and 8-azaguanine on mate-killer paramecia
Authors: Gibson I. , Beale G. H. 
Published: September 2009

1. Mate-killer paramecia (derived from stock 540, P. aurelia) were treated with ribonuclease and 8-azaguanine to determine the effect of these two substances on the mu particles and metagons.2. Ribonuclease destroyed the metagons in living paramecia but had no direct effect on the viability of the mu particles. The latter were however destroyed precisely after one fission of cells whose metagons had been eliminated by ribonuclease treatment.3. Re-synthesis of metagons was found to take place between the second and third fissions after treatment with ribonuclease, if the dominant gene M2 was present.4. Increasing the concentration of ribonuclease in the external medium, or in the duration of exposure of paramecia to ribonuclease, resulted in destruction of increasing proportions of metagons.5. 8-azaguanine did not destroy metagons already present, but destroyed the mu particles immediately.6. It is concluded that the results obtained with these two substances are consistent with the view that RNA is an essential constituent of metagons.
The mating-type substances of Paramecium bursaria
Authors: Cohen L. W. , Siegel R. W. 
Published: September 2009

The detached cilia from sexually reactive cells of Paramecium bursaria will agglutinate with the cilia of intact sexually reactive animals of a complementary mating type. No such reaction will occur if incompetent cells are used or if the cells are of the same mating type. Particulates other than cilia do not adhere to tester cells; the cilia which carry the specific mating-type substances are restricted to the ventro-lateral surface of the animal.Studies of the heat inactivation of the ability of detached cilia to agglutinate confirm in detail the hypothesis of Metz which holds that cell unions leading to conjugation are brought about by the interaction of two pairs of complementary substances, A and a and B and b; the former pair of substances is more heat labile than the latter. The data suggest that animals of each of the four mating types carry a unique combination of two substances, namely, AB, aB, ab, and Ab.
Genetical studies on growth and form in the fowl 1. Phenotypic variation in the relative growth pattern of shank length and body-weight
Authors: Cock A. G. 
Published: September 2009

Body-weight and shank length from 2 weeks of age to adult (and from 8 weeks onwards, shank width) have been measured on 154 fowls all hatched on the same date, belonging to two F1breed crosses: White Leghorn × Rhode Island Red (L × R) and Indian Game × Light Sussex (G × S). After logarithmic transformation the data have first been analysed cross-sectionally (analysis of the age-means for each sex and cross). A longitudinal analysis (fitting a regression line to the data of each individual) has then been made of the approximately linear portions of the curves. The following conclusions are drawn.(1) Growth in shank length relative to body-weight between 2 and 10 weeks conforms closely to simple allometry. The coefficient of ontogenetic allometry (heter-auxesis),k, is approximately 0·4, being 0·02 higher in L × R than in G × S and 0·05 higher in males than in females. In femaleskdeclines (eventually to zero) after 10 weeks; the decline occurs about 4 weeks later in males. For shank width relative to body-weightkis about 0·25.(2) At a given body-weight males have longer and thicker shanks than females; L × R have longer but thinner shanks than G × S.(3) Within sexes and crosses there is highly significant individual variation ink, but the allometry lines do not pass, within the limits of error, through any single point. This implies that variation in relative shank length is complex in its ontogenetic origin.(4) There is no appreciable correlation within sexes and crosses between shank width and shank length at a given body-weight; this implies (as does (2)) that variation is also complex anatomically.(5) Differences in shape and rate-of-change of shape contribute only a small part of the total variation within sexes and crosses; most is due to differences ingeneralsize andgeneralgrowth rate.(6) Shank width at a given body-weight is positively correlated with body-weight at a given age (r= + 0·36 within sexes and crosses). This agrees with the finding that the coefficient of static allometry (allomorphosis) for shank width is much higher than the ontogenetic coefficient. For shank length the ontogenetic and static coefficients are approximately the same.
A failure to induce heritable changes in four generations of the White Leghorn chicken by inter- and intra-specific blood transfusion
Authors: Kosin I. L. , Kato Masaru 
Published: September 2009

1. A three-year study was conducted to test the efficacy of inter- and intra-specific blood transfusions in domestic poultry for inducing heritable changes in the recipients. The latter were pure-bred White Leghorns. Pure-bred Broad Breasted Bronze turkeys and New Hampshire chickens served as blood donors to two distinct lines of recipients. All injections started when the recipient chicks were 2–5 days old. Altogether, more than 3000 chicks from blood injected lines were involved in the study, conducted between 1959 and 1961 and distributed between the parental and three subsequent generations. Each injected chick received a total of some 155 ml. of whole blood in the course of a five-month injection period. An adequate number of control (non-injected) birds was used throughout. Observations were made on plumage colour, body-weight, egg-weight, egg-shell colour, fertility and hatchability. Furthermore, blood plasma and muscle tissue of appropriate birds were subjected to immunological, chromatographic and electrophoretic analyses.2. On the basis of all these criteria, no evidence of heritable shifts in the direction of the donor organism was discerned among birds belonging to either of the two treated lines.
Statistical analysis of chromosome distribution to the poles in interspecific hybrids with variable chromosome pairing
Authors: Sficas A. G. 
Published: September 2009

A probability distribution of chromosome separation to the poles was developed to test the randomness of movement of univalents in asynaptic material where a variable amount of meiotic pairing occurs. Two tables were calculated, one for 24 chromosomes which can be used for any even number equal or less than 24, and the other for 19 chromosomes which can be used for any odd number equal or less than 19.ThreeNicotianahybrids, namelyN. glutinosa×N. otophora, N. glutinosa, N. sylvestris, andN. tabacum×N. glutinosa, and one polyhaploid were investigated. All hybrids had a tendency towards an equal distribution of unpaired chromosomes to the poles. The polyhaploidN. tabacum(with a substitutedN. plumbaginifoliachromosome) had an opposite tendency, i.e. towards a flatter distribution than expected from random distribution of univalents. A short discussion of the problem is given.
A comparison of the interaction, with two types of environment, of pure strains or strain crosses of poultry
Authors: Hull P. , Gowe R. S. , Slen S. B. , Crawford R. D. 
Published: September 2009

In these experiments comparisons were made between the magnitude of the interaction of ‘pure’ strains and strain crosses of poultry with two types of environments—location effects and a restricted-feed versus a full-feed rearing programme. The ‘pure’ strains were closed flocks of White Leghorns that had been selected for increased egg production, while the strain crosses were the reciprocal crosses of all combinations of these pure strains. Data from four separate experiments in four consecutive years used for this study involved 8320 laying birds. Six traits of the adult laying birds were used for these analyses.It was expected that the ‘pure’ strains would differ in performance amongst themselves to a greater extent than the strain crosses, and for the two traits, body-weight at housing and sexual maturity, this was found to be the case in three out of four years. These two traits were affected to the greatest extent by the rearing treatment. Also, the genotype-environment interaction variance was found to be significant and of important magnitude relative to the genetic variance for these two traits. Where the environmental effect was found to be smaller, the interaction variance made up a smaller proportion of the genetic variance.
Transduction analysis using leucine requiring mutants ofSalmonella typhimurium
Authors: Smith-Keary P. F. , Dawson G. W. P. 
Published: September 2009

1. Data is presented in support of the hypothesis that inSalmonella typhimuriumthe fragments participating in the transduction of a particular linkage group arise by breakages at constant positions in the genome of the donor bacteria.2. Data from three factor transduction experiments are used to construct a linkage map of theleu-araBregion which defines not only the relative order of the markers but also the relative distances between them.
The inheritance of lymph proteins in Drosophila
Authors: Pantelouris E. M. , Duke E. J. 
Published: September 2009

The inheritance of three lymph protein fractions separable by starch-plate electrophoresis has been studied. Each fraction is under the control of a separate gene, the dominant allele determining its presence and the recessive its absence.The gene for the fastest fraction is sex-linked, whilst those for the other two are autosomal and linked.
Heterogeneity among spermatogonia ofDrosophila melanogasterin sensitivity to X-rays
Authors: Slizynska H. 
Published: September 2009

1. Sensitivity ofDrosophila melanogastermale germ-cells to chromosome breakage by X-rays has been measured by the structural changes found in the salivary gland chromosomes of larvae from irradiated fathers and untreated mothers. The genetical effectiveness of irradiation on the same males was measured by the frequency of sex-linked lethals.2. Assessed by the overall percentage of germ-cells carrying structural changes, sensitivity follows the well-known pattern: it is highest in spermatids and decreases over spermatozoa and spennatocytes to spermatogonia.3. This overall sensitivity has been analysed on three levels:(a) The proportion in successive broods of ‘positive’ males,i.e.males which respond to irradiation. The results indicate that spermatozoa and spermatids in most or all males are equally sensitive to X-rays, while in regard to spermatogonia the males represent a heterogeneous population consisting of positive and negative males. This is fully confirmed by statistical analysis which was carried out by Dr B. Woolf.(b) The proportion of ‘sensitive’ germ-cells per positive male,i.e.germ-cells carrying at least one structural change. While the proportion of sensitive cells per positive male is about 1:3 for spermatozoa, spermatocytes and spermatogonia, it is higher for spermatids. This is the main reason for the observed increase in overall sensitivity from spermatozoa to spermatids and for its subsequent drop in spermatocytes. On the contrary, the drastic drop in overall sensitivity from spermatocytes to spermatogonia results entirely from a drop in the proportion of positive males.(c) The distribution of breaks in sensitive cells. The clustering of breaks in sensitive cells is highest in spermatogonia, somewhat lower in spermatids, and lowest in spermatocytes and spermatozoa. It indicates that spermatogonial cells are a heterogeneous population, consisting of cells that are either highly sensitive to X-rays or not sensitive at all.4. The fact that the sensitivity of spermatogonia varies both between and within individual males is tentatively attributed to the presence or absence of spermatogonial mitoses.
Genetic analysis of the phosphatases in Aspergillus nidulans
Authors: Dorn G. 
Published: September 2009

Summary1. A histochemical method has been applied to the detection of alkaline and acid phosphatase mutants in single colonies of Aspergillus nidulans.2. With the above method it has been possible to isolate mutants in which the alkaline and acid phosphatase activities are affected either separately or simultaneously.3. Crude extracts of wild-type A. nidulans contain four electrophoretically distinct phosphatase components, two with activity at alkaline pH and two with activity at acid pH. Genes affecting three of the four components have been identified.4. Two suppressor mutants of an alkaline phosphataseless mutant (palB7) have been isolated. In a strain carrying palB7 and one of these suppressors, the restoration of an alkaline phosphatase component is accompanied by loss of the faster acid phosphatase component. In a similar strain carrying the other suppressor, the partial restoration of the alkaline phosphatase component goes with an electrophoretic alteration of the slower acid phosphatase component.5. Genetic analysis of twenty-seven mutants has resulted in the identification of fifteen loci affecting the phosphatases. All these loci have been assigned to linkage groups, and twelve of them were also mapped meiotically in relation to other loci.6. One possible model (based on heteropolymeric proteins) has been proposed to account for the electrophoretic and genetic data on the various phosphatase and suppressor mutations.