bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymorphism at the G6PD and 6PGD loci inDrosophila melanogaster
Authors: Bijlsma R. 
Published: September 2009

SUMMARYThe influence of sodium octanoate on the polymorphism at the loci G6PD and 6PGD inDrosophila melanogasterwas investigated by studying its effect on egg hatchability, larval-to-adult survival and adult survival. The results demonstrate the existence of differences in fitness between the different genotypes of the two loci both for larval-to-adult survival and for adult survival. Furthermore, changes in enzyme activity of both enzymes, brought about by the sodium octanoate treatment, were observed. This makes it highly probable that the observed differences in fitness can be ascribed to the loci themselves and not to linked fitness genes. Finally, this study demonstrates the existence of strong interaction between the two loci with respect to fitness. Epistasis was demonstrated both in the larval-to-adult survival experiment and in the adult survival experiment.
The time of detection of recessive visible genes in small populations
Authors: Robertson Alan 
Published: September 2009

SUMMARYHomozygotes for recessive visible genes have often been discovered in lines under artificial selection, sometimes many generations from the start. As a help in the interpretation of this phenomenon, the distribution of the time to first detection as a homozygote of a recessive gene occurring only once in the initial generation has been obtained. Alternatively the results may be considered as referring to the time of first appearance as a homozygote of a new mutation occurring in a finite population. For a monoecious random mating population of size N with selfing permitted, the mean time to detection is very close to 2N⅓ over a range of N from 1 to 500 with a coefficient of variation of roughly 2/3 and a 95% upper limit about 2·5 times the mean. If selfing is prohibited, the mean time is increased by a little over 1 generation. The treatment is extended to cover the effects of artificial selection in favour of the heterozygote, of the frequency of occurrence in the initial generation and of the examination of more individuals each generation than are used as parents.
Mapping of the pneumococcus chromosome: differences between recipient strains varying inhexproperty and the location of theopt-r2gene
Authors: Butler L. O. , Nicholas G. , Grist R. W. 
Published: September 2009

SUMMARYTransformation studies in pneumococcus had shown that loci determining the resistance to erythromycin and streptomycin were unlinked when strain Cl3 was recipient but linked when strain SIII-I was recipient. This phenomenon also applies to other pairs of markers studied in these two recipients, no matter whether the transforming DNA was derived from strain Cl3 or strain SIII-I. Other differences between the two recipient strains were also revealed. Whereas competent cultures of strain Cl3 were composed of all competent cells, which was in agreement with previous reports of pneumococcal cultures, strain SIII-I normally gave a maximum average of 28% competent cells. Strain SIII-I was unstable, since on repeated sub-culturing the competence peak profile changed and the value of ‘fcq’ increased. These properties were reflected in the twohex−strains 401 and R6x which were found to be similar to the ‘altered SIII-I’ strain. The results from the linkage studies have been applied to the chromosome map and have placed theopt-r2gene in thestr-r41-containing chromosome arm.
Comparing the means of inbred lines with the base population: a model with overdominant loci
Authors: Minvielle Francis 
Published: September 2009

SUMMARYFor one-, two- andn-locus models of a quantitative trait assumed to be determined by overdominant loci, it is shown that the mean of an inbred line will be equal to or larger than the mean of the base population if the original gene frequencies satisfy a condition which is generally a function of the degree of overdominance and of the genotypic values.
At-haplotype (tw75) overlapping two complementation groups
Authors: Artzt Karen , Babiarz Bruce , Bennett Dorothea 
Published: September 2009

SUMMARYThe recessive lethal T/t-complex haplotypetw75was isolated from Jena, East Germany, prior to 1973. It was at first thought to be a standard member of thetw5complementation group because matings ofT/tw75×T/tw5produced tailless offspring only (Dunn, Bennett & Cookingham, 1973). Cross tests with all other complementation groups and embryological studies have recently been completed, with results demonstrating thattw75does not complement the members of either thetw5or thetw1complementation groups. Histological studies show that compound embryostw75/tw5andtw75/tw1die with symptoms indistinguishable fromtw5/tw5andtw1/tw1homozygtes respectively. Thustw75represents the first confirmed isolation of at-haplotype that overlaps two complementation groups.
Variation forXchromosome expression in mice detected by electrophoresis of phosphoglycerate kinase
Authors: West John D. , Chapman Verne M. 
Published: September 2009

SUMMARYThe proportions of the two isozyme bands of the X-linked form of phosphoglycerate kinase (PGK-1) were compared in 16 tissues from four groups of adult heterozygous females. Little evidence was found for differences in expression of the two isozymes among tissues but there was a marked difference among the four groups of mice. The proportion of the PGK-1B enzyme was consistently lower in PGK-1AB heterozygous daughters of C3H/HeHa females than in corresponding heterozygotes with a C57BL/6Ha, DBA/2Ha or JBT/Jd mother. This difference was also observed in foetuses on the fourteenth day of gestation irrespective of whether the C3H/HeHaXchromosome was derived from the mother or the father. Sequential sampling of blood from the same heterozygous females provided no evidence for genetically determined cell selection in the adult erythropoietic tissue. The observed differences probably reflect variation at anX-chromosome controlling element locus among inbred strains of mice, similar to that described by Cattanach & Williams (1972) usingX-linked morphological markers, although this has yet to be tested.
The rate of mutant substitution in populations with overlapping generations
Authors: Pollak Edward 
Published: September 2009

SUMMARYWe consider an age-structured population that is observed at timest= 0, 1, 2,…. It is assumed that for eachtthere is the same number of individuals of a particular sex and age group. Another assumption we make is that an offspring of a specified sex has at all times the same probability of having a parent of a particular age and sex. It is shown that the rate of substitution of neutral mutants is/L, whereandLare respectively equal to the mean fraction of mutants among gametes succeeding in forming newborn individuals and the mean age of reproduction. This result also applies to monoecious populations. The substitution rate is also derived for advantageous mutants in a monoecious population. Once again, the mutation rate in the usual expression is replaced by/L. Implications of these results are discussed.
Studies of esterase 6 inDrosophila melanogaster: XI. Modification of esterase 6 activity by unlinked genes
Authors: Tepper Craig S. , Richmond Rollin C. , Terry Anne L. , Senior Alayne 
Published: September 2009

SUMMARYThe often remarkable similarity in structural gene products among related species has led to the hypothesis that species differences may reside largely in changes at regulatory gene loci. This hypothesis assumes that groups capable of speciating have allelic variation at regulatory loci in their natural populations. We have undertaken an analysis of the mode of regulation of theesterase 6(Est 6) locus inDrosophila melanogasterto determine the nature and extent of regulatory gene variation in natural populations. Analyses of esterase 6 (EST 6) activity among strains carrying the same thermostability variants reveal that significant, specific-activity differences are present. Reciprocal crosses between lines having high and low EST 6 activity show that loci other than theEst 6structural gene influence EST 6 activity. Analyses of male hybrids from crosses betweenD. melanogasterandsimulansindicate that theXchromosome of these flies affects the expression of theEst 6locus, resulting in unequal levels of enzyme activity from the two alleles. The effect is sex and tissue specific. Female hybrids carrying theXchromosomes of both species exhibit equal expression of the twoEst 6alleles. We have determined whether natural populations are polymorphic forXchromosomes which affect EST 6 activity by extracting singleXchromosomes from wild-collected males and placing these chromosomes in identical genetic backgrounds. Stocks which are otherwise genetically identical but carry independently derivedXchromosomes show significant differences in the activity of EST 6. These data suggest that regulatory loci may be commonly polymorphic in natural populations.
Predictions of response to artificial selection from new mutations
Authors: Hill William G. 
Published: September 2009

SUMMARYThe pattern of response expected from fixation of mutant genes for quantitative traits in finite populations is investigated for a range of distributions of mutant gene effects. The eventual rate depends on the total variance of mutant effects per generation, but the initial rate and the variance of response is higher if the distribution of mutant effects has a large standard deviation or is leptokurtic. The difference between initial and eventual rates of response is greater with large population sizes.For a range of assumptions, new mutants are unlikely to have much influence on response for 20 or so generations, but then may contribute substantially, such that no plateaux are obtained. However, information on the variance contributed by mutants is almost entirely on bristle number inDrosophila.It is argued that the role of new mutants should be considered in designing breeding programmes, in particular in utilizing large populations.
Genetics ofAspergillus flavus: complementation and mapping of aflatoxin mutants
Authors: Papa K. E. 
Published: September 2009

SUMMARYMutants ofAspergillus flavusimpaired in aflatoxin production were induced withN-methyl-N′-nitrosoguanidine and analysed by means of the parasexual cycle. The gene symbolaflwas assigned to this type of mutation. Diploid complementation tests revealed that most of 14aflmutants belonged to different complementation groups. One mutant (afl-1) failed to complement or only partially complemented all other mutants. Haploidization of one diploid revealed the independent segregation of twoaflmutants. Heterozygous diploids were synthesized between twoaflmutants and tester strains genetically labelled on eight linkage groups. Haploidization of the diploids led to the assignment of two aft mutants to linkage groups. Linkage ofafl-4 tow+andafl-1 toleuon linkage groups II and VII, respectively, was demonstrated.
The time of detection of sex-linked recessives in small populations
Authors: James J. W. 
Published: September 2009

SUMMARYA sex-linked recessive gene with visible effect will first be detected in the hemizygous sex (male). In lines with equal numbers of males and females, when the gene is initially present in a single female the probabifity of detection falls from 2/3 in single pair lines to 0·54 in large lines. The mean and standard deviation of time to detection are almost independent of population size, being about 4/3 and 2/3 respectively. About 98% of all detections occur within three generations, so a gene detected much later than this after the foundation of a selection line is likely to be a new mutant. Higher initial frequencies and selection favouring heterozygotes increase the chance of detection. The time taken is decreased with higher initial frequencies and increased slightly by selection favouring heterozygotes.
Immunogenetics of an antigen identified in both sheep and cattle sera
Authors: De Benedictis Giovanna , Capalbo P. , Gallina E. 
Published: September 2009

SUMMARYAlloimmunization in sheep revealed an antigen specificity B1 which is also to be found in cattle sera. The molecular weight of the protein carrying B1 was greater in sheep than in cattle, whilst in both cases its isoelectric point was at pH 6·2. The electrophoretic position of the antigen suggests that the molecule carrying B1 might be a β-globulin. Family studies indicated that in both species B1 was inherited in a simple Mendelian manner, as if it were a product of a dominant alleleB1at an autosomal locusB.
Isolation and characterization of a new class of amino-acid-analogue-resistant mutants inAspergillus nidulansusing reduced carbon flow
Authors: Singh Mahavir , Sinha Umakant 
Published: September 2009

SUMMARYFour recessive amino-acid-analogue-resistant mutants were isolated on a medium containing acetate as the sole carbon source and the amino acid analogues p-fluorophenylalanine and ethionine. None of the mutants showed any growth requirement. Analysis of growth on media containing an amino acid as the sole nitrogen source indicated that two mutants out of the four possess normal systems for utilization of acidic, neutral, basic and aromatic amino acids. The mutantsfpa70 andfpa71 showed reduced growth on tryptophan as the sole source of nitrogen. Three new loci, identified after preliminary genetic analysis, were located on three linkage groups: one each on linkage groups I, VI and VIII.
Artificial induction of autogamy inParamecium caudatum
Authors: Tsukii Yuuji , Hiwatashi Koichi 
Published: September 2009

SUMMARYThree methods of artificial induction of autogamy inParamecium caudatumwere described: (1) treatment with KCl+papain, (2) treatment with KCl and then with KCl + papain and (3) ordinary mating reaction and then treatment with papain. As expected, one-to-one segregation ratios were obtained in the progeny from the parents heterozygous for the two loci: mating type and lactate dehydrogenase. A high rate of autogamy is induced by method (1), but its use is restricted to only a few clones. Autogamy is also induced at a high rate by method (2), by which the induction is more stable. Autogamy is induced at a lower rate by method (3), but this method can be widely applied to every species ofParameciumwhich has complementary mating types. Some exautogamous progeny become completely sterile through successive autogamy. The cause of this sterility is discussed.
Genetic differences of DNA and RNA synthesis in the epithelium of the lens of the chick
Authors: Randall F. E. , Truman D. E. S. , Clayton R. M. 
Published: September 2009

SUMMARYThe genetically unrelated chick strains Hy-1 and Hy-2, which have been strongly selected for growth rate, both exhibit hyperplasia of the lens epithelium. These two strains and a control strain N, not selected for growth rate, were compared with respect to incorporation of3H-thymidine and14C-uridine by freshly excised lenses in culture at different times throughout a 24-h period. The levels of incorporation of label into the lens cells were found to vary according to the time of day. The pattern of diurnal variation in both thymidine and uridine incorporation was found to be strain specific. Hy-1 and Hy-2 showed a greater degree of synchrony than did normal (N) lenses, and the frequency of the peaks of incorporation was also higher. Autoradiography confirmed that only lens epithelium incorporates thymidine during culture and that the number of labelled nuclei depends on the time of day when the lenses were explanted. These data point to genetic control of the cell cycle.
Selection for ethanol tolerance andAdhallozymes in natural populations ofDrosophila melanogaster
Authors: Hickey D. A. , McLean Michael D. 
Published: September 2009

SUMMARYAlcohol dehydrogenase (Adh) allozyme frequencies and tolerance of adult flies to ethanol were measured in population samples ofD. melanogasterfrom a winery in Southern Ontario. Samples were also tested from a number of non-winery sites.Adhfastfrequencies decrease as one moves away from the winery, but this drop in allozyme frequency is statistically significant only for those areas that are more than 3 km distant from the winery. Tolerance of adult flies to ethanol also differed between winery and non-winery populations, but these differences were not statistically significant. The data presented here may help to resolve the seeming conflict between the two previous studies ofAdhallozyme frequencies in natural populations from highand low-alcohol environments.
‘Overcompensation’ at an enzyme locus inDrosophila pseudoobscura
Authors: Toŝić Mirjana , Ayala Francisco J. 
Published: September 2009

SUMMARYThe experiments reported in this paper are primarily addressed to test the hypothesis of overcompensation; i.e. whether polymorphic populations exploit limiting environmental resources better than populations uniform for a single genotype. Overcomposition is an ecological consequence of some models of frequency-dependent selection. Secondarily, the experiments investigate whether overdominance exists at theMdh-2locus inDrosophila pseudoobscura.Two types of experimental populations are established: ‘low-variability’ populations, in which all flies in a culture are offspring from only two laboratory strains; ‘high-variability’ populations, in which the flies in a culture are derived from 20 different strains. However, the overall degree of individual heterozygosity is the same in both types of populations. Three kinds of populations with respect to theMdh-2locus are established within each type; two are homozygous for either the100or the112allele, the third is heterozygous. A fourth kind of population exists among the high-variability populations; namely, populations in which all threeMdh-2genotypes are present. The experiments are done at two densities; one quasi-optimal, the other highly competitive.Populations with high overall levels of genetic variation consistently produce more flies than low-variability populations. The differences are significant at the low, but not at the high, density. Moreover, populations polymorphic for theMdh-2locus generally produce more flies than populations having only oneMdh-2genotype. At high density, theMdh-2polymorphic populations have greater productivity than populations with anyone of the three genotypes, and the differences are statistically significant when the polymorphic populations are compared with either one of the two homozygotes or with the average of all three genotypes. In brief, overcompensatory effects – which may account for frequency-dependent selection – are observed in the experiment and may be a common phenomenon in nature.Populations in which all individuals are heterozygous at theMdh-2locus produce in every case more flies than populations with only homozygotes for one or the other allele. The superiority of the heterozygotes is statistically significant for all comparisons at low density, but at high density it is statistically significant for the comparison with the homozygote rarer in nature and only in low variability populations.
On the nonautonomy of the small-kernel phenotype produced by B–A translocations in maize
Authors: Birchler James A. 
Published: September 2009

SUMMARYSeveral of the B–A translocations of maize produce a small-kernel phenotype which is associated with hypoploid endosperms from fertilizations by sperm which result from nondisjunctional events of the B centromere at the second microspore division. Lin (1975) demonstrated that the small-kernel phenotype was not a consequence of the deficient nature of said endosperms, but involved a differential effect of male and female chromosomal regions.The TB-A effect has been examined for evidence of autonomy in mosaics for the most extreme such case known, i.e. the small-kernel effect produced by the compound B–A translocation, 1La-5S8041. Although reduced-sized kernels are formed when the paternal contribution of the 1L-5S element is totally lacking from the endosperm, sectorial loss has no detrimental effect on dry weight. This phenomenon is therefore considered to be nonautonomous.
Protein variation and duplicate loci in the Atlantic salmon,Salmo solarL.
Authors: Cross T. F. , Ward R. D. 
Published: September 2009

SUMMARYA natural population of Atlantic salmon,Salmo salarL. was screened for genetic variation at 59 protein loci, using a sample of parr, the juvenile freshwater stage. The mean heterozygosity per locus, estimated at 0·033 ± 0·014, is similar to that described in other salmonid species but low for fish species in general. Variation was observed at AAT, IDH, MD–ME, GLO, ADA, and SDH loci. The methods described should prove useful in stock discrimination and in producing salmon for restocking and sea-rearing. The observed extent of gene duplication is discussed in relation to the evolution and systematics of the salmonid fishes.
Population dynamics and the evolution of sex-determination in lemmings
Authors: Carothers A. D. 
Published: September 2009

SUMMARYThe hypothesis is advanced that the evolutionary stability of the unusual sex-determining mechanisms of the Wood Lemming (Myopus schisticolor) and of the Varying Lemming (Dicrostonyx torquatus) is a direct consequence of certain characteristic features of their population dynamics, and that these include phases of unrestrained population growth and of mass dispersal. Computer simulations confirm the feasibility of such an explanation. Predictions of this hypothesis are found to differ in a potentially testable manner from those of the ‘inbreeding’ hypothesis of Stenseth (1978). The demonstration of such a direct link between population ecology and evolutionary genetics would, if substantiated, be exceptional in mammals.
Controlling elements in the mouse: IV. Evidence of non-randomX-inactivation
Authors: Johnston P. G. , Cattanach B. M. 
Published: September 2009

SUMMARYThe non-randomXchromosome expression that has been observed with coat markers in female mice heterozygous for theXcealleles,XceaandXceb, has now been investigated with the electrophoretic enzyme marker,Pgk-1. Because theXcestatus of thePgk-1amarked chromosome was not known, PGK expression was assessed inPgk-1a/Pgk-lbheterozygotes which carried eitherXceaorXcebon theirPgk-1bchromosome. The PGK-1A allozyme was found to predominate in both genotypes but whenXcebwas present on thePgk-lbchromosome the expression of the two allo-zymes was less unequal. This effect was seen in both liver and kidney of adults and to at least the same degree in embryos aged 13·5 and 7·5 days. The results have been interpreted to mean that the non-randomXexpression derives from a primary non-randomness of theXinactivation process and that a new and more extremeXceallele, designatedXcec, was present on thePgr-1a-markedXchromosome.
Controlling elements in the mouse: V. Linkage tests with X-linked genes
Authors: Cattanach B. M. , Papworth D. 
Published: September 2009

SUMMARYPrevious studies have shown that the mouseXchromosomal locus,Xce, which causes non-randomXchromosome inactivation, is closely linked to the Is(X; 7)CtX-autosome translocation. This has placed it either nearTaon one side of the breakpoint or nearjpon the other. Linkage tests withMovbrandTanow demonstrate that the locus in fact lies close toTa. The data also provide genetic evidence which establish that the C3H/HeHXchromosome carries theXceaallele of this gene and the JU/FaCt and C57BL/GoHXchromosomes carry theXceballele, and further suggest that theX-linked modification of the heterozygous phenotypes ofX-linked genes observed by various other investigators are all attributable to differences at theXcelocus. Evidence of a maternal influence uponMovbrphenotypes is also presented. This appears to operate independently of theX-inactivation process, probably through an effect of differing levels of copper in the milk in early life upon the mutant coat colour in the young.