bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in genetic constitution and sterol composition during growth of nystatin-resistant heterokaryons ofNeurospora crassa
Authors: Ogden Jill E. , Grindle Morris 
Published: September 2009

SUMMARYHeterokaryons ofN. crassawere synthesized from homokaryotic strains differing in sterol composition and sensitivity to the polyene antibiotic nystatin. Mycelia of the nystatin-sensitive strainerg-1+contained ergosterol and episterol, and the nystatin-resistant mutanterg-1 contained fecosterol and lichesterol. Mycelia of heterokaryons with different proportions oferg-1+:erg-1 nuclei contained various proportions of the four sterols. Ergosterol was the principal sterol in heterokaryons with more than 5%erg-1+nuclei.Heterokaryons with various proportions oferg-1+:erg-1 nuclei were grown for several weeks along tubes of synthetic media. Growth rates were stable on minimal medium and nutritionally supplemented media but nuclear proportions often fluctuated. Growth rates fell sharply on nystatin-supplemented media and there were adaptive increases in proportions of mutanterg-1 nuclei which resulted in selection of nystatin-resistant homokaryotic mycelia.
Bar reversion and hybrid dysgenesis inDrosophila melanogaster:reversion in males and in inversions
Authors: Colgan D. J. 
Published: September 2009

SUMMARYThe effect of the P-M system of hybrid dysgenesis inDrosophila melanogasteron unequal crossing-over was studied using the Bar duplication. This system of dysgenesis had no demonstrable effect on the rate of Bar reversion. In the course of the study it was found that there was a greatly reduced rate of reversion in two homozygous inversion stocks. Further, one revertant was found which may result from unequal crossing over at the Bar locus in males.
The Cincinnati Lipid Research Clinic family study: Bivariate path analyses of lipoprotein concentrations
Authors: McGue M. , Rao D. C. , Reich T. , Laskarzewski P. , Glueck C. J. , Russell J. M. 
Published: September 2009

SUMMARYMethods for the analysis of the joint transmission of two phenotypes are described and used to determine the extent to which lipoprotein concentrations share a common genetic and/or environmental background. Analysis of data on 160 Caucasian nuclear families revealed that the observed phenotypic association between high-density cholesterol (HDL) and low-density cholesterol (LDL) could be accounted for in terms of common family environmental effects alone (estimated genetic correlation, ρG = −0·132±0·136; estimated residual environmental correlation, ρR = 0·065±0·230). The association between HDL and very-low-density cholesterol (VLDL) could not be accounted for in terms of family environmental effects alone. For HDL and VLDL the residual environmental correlation was significant while the genetic correlation was not (ρG = −0·111±0·214, ρR = −0·421±0·172). The correlation between LDL and VLDL also could not be accounted for in terms of common family environmental effects alone, although here a genetic relationship appears to be the important factor (ρG = 0·330±0·192, ρR = 0·010±0·217).
The number of loci affecting a quantitative trait in Drosophila melanogaster revealed by artificial selection
Authors: Gallego Araceli , López-Fanjul Carlos 
Published: September 2009

SUMMARYIndividual and within-full-sib family selection for low sternopleural bristle number was carried out for 17 generations, with six replicate lines for each selection method. Our results can be summarized as follows: (1) the response to selection was exhausted very quickly, (2) the additive variance of the selected lines declined rapidly, (3) the variation in response to selection decreased as selection progressed, (4) genetic differences among replicates at the selection limit were small, (5) individual selection resulted in a higher initial response than within-family selection, but similar limits were achieved with both procedures. These observations are consistent with the hypothesis that the pattern of response to selection is due to the segregation in the base population of only a few loci with large effects, at intermediate frequencies.
Contrasted, a steel allele in the mouse with intermediate effects
Authors: Beechey C. V. , Searle A. G. 
Published: September 2009

SUMMARYThe steel allele, contrasted (Slcon), arose in a neutron irradiation experiment.Slconis fully penetrant and heterozygotes can be recognized at or soon after birth by darkly pigmented external genitalia in both sexes, while the adult coat tends to be a little lighter than normal. Homozygotes also have dark genitalia and a markedly diluted coat. Both eumelanin and phaeomelanin are affected, with reduced numbers of cortical and medullary pigment granules in the hairs. Contrasted also affects the haematopoietic system, causing slight macrocytic anaemia in the homozygote.Slconhomozygous males are fertile but testes weigh on average 20% less than in their heterozygous litter-mates. Homozygous females are usually sterile although if mated early (4½−6 weeks) they occasionally have a single litter. Ovarian sections showed a gradual degeneration of oocytes in Graafian follicles so that most had gone by 2 months. Similarly, vaginal smears indicated that after about three normal cycles homozygous females lapsed into a state of persistent dioestrus; injections with gonadotrophins did not prolong their period of fertility or cause a resumption of their oestrous cycles. The effects on fertility, pigmentation and haematology of contrasted when combined with other steel alleles are also described.
Variance component analysis for viability in an isolated population ofDrosophila melanogaster
Authors: Tachida Hidenori , Matsuda Muneo , Kusakabe Shin-Ichi , Mukai Terumi 
Published: September 2009

SUMMARYUsing the 602 second chromosome lines extracted from the Ishigakijima population ofDrosophila melanogasterin Japan, partial diallel cross experiments (Design II of Comstock & Robinson, 1952) were carried out, and the additive genetic variance and the dominance variance of viability were estimated. The estimated value of the additive genetic variance is 0·01754±0·00608, and the dominance variance 0·00151±0·00114, using a logarithmic scale. Since the value of the additive genetic variance is much larger than expected under mutation–selection balance although the dominance variance is compatible with it, we speculate that in the Ishigakijima population some type of balancing selection must be operating to maintain the genetic variability with respect to viability at a minority of loci. As candidates for such selection, overdominance, frequency-dependent selection, and diversifying selection are considered, and it is suggested that diversifying selection is the most probable candidate for increasing the additive genetic variance.
Population genetics of extranuclear genomes under the neutral mutation hypothesis
Authors: Takahata Naoyuki 
Published: September 2009

SUMMARYPopulation genetics of extranuclear genomes is further developed under the neutral-mutation random-drift hypothesis, and the characteristic evolutionary aspects are summarized. Several formulae derived here are concerned with the variances of genetic variability (gene identity) at a single extranuclear locus and the evolutionary distance between two isolated populations which is estimated from a comparison of homologous linked nucleotide sites. Two types of variance are considered; one is the variance in the entire population (VQ) and the other is the variance within a single germ cell (VH). When compared with a Mendelian genetic system in a panmictic population, an extranuclear genetic system has the following equilibrium properties: (1) the mean genetic variability is low if, despite the high multiplicity of the genome in a cell, the proportion of the cytoplasmic contribution from the male's gamete is small, (2) the effect of recombination is small and a large amount of variance of linkage disequilibrium tends to be maintained, (3) the overall relationship between the mean and variance of genetic variability does not much differ butVQ(VH) is expected to be small if the paternal contribution is small, and (4) the evolutionary distance estimated depends on the extent of intrapopulational variation in a common ancestor population which in turn depends on within-cell variation. I argue that there is an analogy between the model of extranuclear genomes in a finite population and that of nuclear genes in a subdivided population. The analogy helps our understanding of some properties in an extranuclear genetic system.
Evolutionary dynamics of extranuclear genes
Authors: Takahata N. , Slatkin M. 
Published: September 2009

SUMMARYWe studied the evolutionary dynamics of extranuclear genes taking into account simple kinds of selection, two modes of inheritance and the multiplicity of genomes within a cell. Particular attention was paid to the accumulation of advantageous or deleterious mutations in an extranuclear genome. Within-generation drift due to multiplicity of genome and non-Mendelian segregation promotes the fixation of advantageous mutations and prevents deleterious mutations from accumulating. We show also that the extent of paternal contribution makes little difference in the rate, but, in contrast, the configuration of the genome and the mode of transmission both makes a large difference. These results are compatible with what is known about extranuclear genomes.
Recombination between two mouset-haplotypes (tw12tfandtLub-1): segregation of lethal factors relative to centromere and tufted (tf) locus
Authors: Condamine Hubert , Guénet Jean-Louis , Jacob François 
Published: September 2009

SUMMARYRecombination between two mouset–haplotypes,tw12tfandtLub-1, was investigated by screening the tailless progeny of the cross ♀tw12tf/tLub-1+ × ♂Ttf/+tffor the segregation of tufted phenotype,tw12andtLub-1lethal factors, and metacentric chromosome (sincetLub-lhaplotype is associated with a Robertsonian fusion involving chromosomes 4 and 17). The results give a 17% estimate of the recombination frequency between centromere andtf, withtLub-llethal factor mapping about two-thirds of the distance from centromere totfand thetw12lethal factor behaving as if closely linked totf. This further extends the findings of Silver & Artzt (1981) and of Artzt, McCormick & Bennett (1982), and shows that twot–haplotypes with quite independent laboratory histories recombine at a normal level, supporting the notion that allt–haplotypes basically share the same structure.
Ribosomal suppressors inPodospora anserina: evidence for two new loci by means of a new screening procedure
Authors: Dequard-Chablat Michelle 
Published: September 2009

SummaryI describe here a new screening procedure to isolate ribosomal suppressors inPodospora anserina. I have used the sporulation defect displayed by an antisuppressor mutationAS7–2. The revertants able to sporulate are due to either true reversions or external mutations. The mutations which restore most efficiently the sporulation show all the properties of ribosomal suppressors and are localized in two new suppressor locisu11andsu12.
Complementation ofnpfmutations in diploid amoebae ofPhysarum polycephalum: the basis for a general method of complementation analysis at the amoebal stage
Authors: Anderson Roger W. , Youngman Philip J. 
Published: September 2009

SummaryHaploid amoebae ofPhysarum polycephalummay form plasmodia by crossing, a sexual process that involves cellular and nuclear fusions, or by selfing, an asexual process in which the development of a single amoeba into a plasmodium may involve neither cellular nor nuclear fusion. Mutant strains (npf) in which selfing is suppressed were previously assigned to several functional groups on the basis of their ability to cross with one another in certain combinations. In the present study hybrid, diploid amoebae were isolated from both crossing-compatible and incompatible mixtures ofnpfmutants. The diploid amoebae from mixtures of compatible strains readily formed plasmodia by selfing, but selfing was suppressed in the diploids from incompatible mixtures. Thus the crossing tests betweennpfmutants may be viewed as complementation tests: their results reflect the differing selfing abilities of the hybrid, diploid amoebae that formed in each mixture. Genetical and environmental factors affecting the efficiency of formation of diploid amoebae were studied, and the diploids were shown to be stable during repeated subcultures. Although diploid amoebae carrying complementingnpfmutations readily formed plasmodia by selfing at 26 δC, they could be cultured without plasmodium formation at 30 δC, a temperature that also inhibited selfing of the haploidnpf+strains. Ways are discussed of exploiting this combination of properties in a general procedure for isolating and testing diploids for dominance and complementation of amoebal mutations inP. polycephalum.
Segregation of centricY-autosome translocations inDrosophila melanogaster: I. Segregation determinants in males
Authors: Falk Raphael , Baker Shula , Rahat Ana 
Published: September 2009

SummaryA special screening procedure for the detection of induced Y-autosome translocations with centric breakpoints was applied. A series of Experimental stocks was constructed, each containing a different half of one of the induced T(Y; 2)'s (T element). The three other elements that were involved in the segregation experiments in each stock were a sex chromosome (X element), an inverted chromosome 2 (A element), and a free arm of chromosome 2 (F element). It is not feasible to determine the relative frequencies of all the 16 possible gamete types by mating an Experimental stock to one tester, nor to different testers that have each at least one class of progeny of the same genotype. Each Experimental stock was mated to four different Tester stocks and the data were calibrated so that a coherent segregation pattern could be obtained.Segregation patterns in meiosis of males from 15 Experimental stocks, each with a different T element were studied. In most Experimental stocks the T element was of the left autosomal arm, while the F element was of the right autosomal arm. In four Experimental stocks the X element segregated independently of the A, F and T elements. In these Group 1 stocks, both the F and the T elements disjoined regularly from the A element. It was concluded that the T element of these stocks had no sex-chromosome disjunction determinants (‘S-determinants’) to interact with the determinants on the X element. Both the T elements and the F elements carried autosomal disjunction determinants (‘H-determinants’) that secured the segregation of the autosomal elements. The H-determinants of the left autosomal arm were qualitatively different from those of the right arm.In the remaining 11 Group-2 Experimental stocks the X and T elements disjoined regularly, indicating the presence of S-determinants on the T elements of these stocks. The segregation of the T and the A elements in these stocks varied from nearly complete dependence to complete independence. It was concluded that this gradation reflected differences in the quantity of H-determinants present on the T elements of these Experimental stocks. It was impossible to discriminate between a model of continuous H determinants activity and one of a finite discrete number of determinants. The results do not agree with the claim that there are no autosomal disjunction determinants in the proximal heterochromatin of chromosome 2.The S-determinants on theBsYy+chromosome were located both adjacent to the centromere and distally on the long arm. The latter were probably translocated to the Y chromosome together with theBsmarker.
Metaphase position and orientation of an interchange quadrivalent of Allium triquetrum: II. Changes in position with changes in percentage alternate orientation
Authors: Rickards Geoffrey K. 
Published: September 2009

SummaryThe position and orientation of an interchange quadrivalent in flattened lateral views of metaphase I were studied in inflorescences of an interchange heterozygote of Allium triquetrum showing high, medium and low alternate orientation frequencies. As the overall frequency of alternate orientation changes in these different inflorescences so the positioning of the alternately oriented quadrivalents changes, in that it becomes more like that of the adjacent quadrivalents. The present data argue for the biological significance of the position/orientation data, and imply the presence of two components of alternately oriented quadrivalents with different positional characteristics.
Effect of phosphate levels on the synthesis of acid phosphatases (EC 3.1.3.2) inNeurospora crassa
Authors: Rodrigues Sergio A. , Rossi Antonio 
Published: September 2009

SummaryWhen grown on high-phosphate medium, the wild-type strain 74A ofN. crassasynthesized two acid phosphatases, as shown by DEAE -cellulose chromatography. These purified enzymes showed heterogeneity on PAGE, low specific activities towards PNP-P, molecular weight values of at least 300000, no deviation from Michaelian behaviour, and great stability in 50 mM sodium acetate buffer, at pH 5·4, when kept at 54 °C. These acid phosphatases were synthesized in reduced amounts or not at all when the mould was grown under conditions of phosphate starvation, indicating that the level of phosphate also regulates the synthesis of the high molecular weight enzyme forms. When grown on high phosphate medium, thepho-3mutant strain also synthesized two acid phosphatases, whose purified enzymes showed no pronounced differences when compared to those synthesized by the wild-type strain in terms of electrophoretic analysis, specific activities towards PNP-P, molecular weight values, and Michaelian behaviour. However, one enzyme form had a higherKmvalue and a lower heat stability than the corresponding enzyme of the wild-type strain. Even though thepho-3locus might not be responsible for an alteration in the primary structure of the repressible acid phosphatase, it seems clear that the enzymes synthesized by the mould grown on low-or high-phosphate medium must share some structural features. Thus, the drastic differences observed in the molecular properties of the enzymes synthesized by the mould grown under conditions of phosphate starvation as opposed to phosphate repression might be due to an effect exerted by the level of inorganic phosphate in regulating the translation, post-translational modifications and/or excretion, but not necessarily the gene-directed synthesis of distinct mRNAs.
Tests of hypotheses on recombination frequencies
Authors: Morton N. E. , MacLean C. J. , Lew R. 
Published: September 2009

SummaryData fromNeurospora,Drosophila, and the mouse support the mapping parameter conventionally used for man, exclude the Haldane, Kosambi, and Carter—Falconer functions, and suggest a refinement for centromere mapping. Different sexes, chromosome arms, and types of data are surprisingly consistent. Double recombination frequencies are accurately predicted, but triple recombination frequencies are overestimated. The centromere appears to act on interference as an obligatory chiasma. Recombination across the centromere conforms to a simple approximation, based on the interval Markov assumption with a common mapping parameter. These results imply that mapping ofnloci requires estimation of at mostnparameters, and the relation between map distances and all recombination frequencies is explicit.
Genetic experiments on sisomicin production byMicromonospora rosea
Authors: Gadó István , Bokány Antónia , Szvoboda György 
Published: September 2009

SummaryChromosomal localization of a gene involved in sisomicin production ofMicromonospora rosean.sp. was suggested by the results of matings between antibiotic producer and non-producer auxotrophic mutants. The frequency of producers among prototrophic recombinants varied with the chromosomal markers used for selection. Thesisallele of the parent which was able to overgrow its partner in mixed culture predominated amongst the recombinants.
Cellular autonomy of hyperactivity in segmentalXchromosomal aneuploids ofDrosophilaand dosage compensation
Authors: Prasad-Sinha Jayashree , Mukherjee A. S. 
Published: September 2009

SUMMARYTranscription in 9A–11A aneuploid mosaic female larvae ofDrosophila melanogasterhas been assessed autoradiographically. Eleven larvae were found to exhibit mosaicism out of sixty-six larvae scanned and the percentage ofXOandXXnuclei varied from approximately 9 to 100. Irrespective of the number ofXXnuclei present theXOnuclei (duplicated for 9A–11A) invariably showed hyperactivity for both the segments. TheXXnucleus exhibited a dosage effect for all the three segments of 9A–11A. Results support the transcriptional constancy of the entireXchromosome, as proposed by Maroni and Lucchesi. Cellular autonomy of hyperactivity of the singleXchromosome even at the level of segments of theXis thus evident from the present results.
Cell autonomy of two DNA-repair mutations inDrosophila melanogaster
Authors: Ripoll Pedro , Kennison James A. 
Published: September 2009

SUMMARYBy means of genetic mosaics we have studied the cell autonomy ofmei-41andmei-9, two loci involved in DNA metabolism. The frequency of spontaneous somatic spots resulting from unrepaired chromosome damage and the sensitivity of mutant cells to killing by X-irradiation - two traits indicative of deficient DNA repair - have been analysed at the cellular level. The results show that: (1) The effect of both mutations on chromosome stability is cell autonomous. (2) After 1000 r of X-irradiation practically all the cells homozygous formei-41disappear while about one-third of the cells homozygous formei-9asurvive the irradiation. The possibility of using these mutants as tools to approach developmental problems is discussed.
Inherited cataracts in inbred mice
Authors: West John D. , Fisher Graham 
Published: September 2009

SUMMARYExamination of the eyes with a slit lamp revealed that 101/H mice had a coloured cataract. Crosses to C3H/HeH indicated that this was inherited as a single recessive gene which we have designated lop-2 (lens opacity-2). The related strain 129/Sv-SlJ-CP had a phenotypically identical cataract and presumably also carries the lop-2 gene. CBA/H, CBA/CaH- + /p, CBA/H-kd and CBA/H-T6 mice had a bright white or white/green cataract that typically extended from the nucleus to the anterior cortex of the lens. Crosses to C3H/HeH indicated that this was inherited as a semi-dominant gene. However, other crosses raise the possibility that the CBA cataract is also caused by lop-2. If so, the expressivity (and penetrance of the heterozygote) is affected by genetic background. Neither lop-2 nor the gene responsible for the CBA cataract was linked to contrasted (Slcon) on chromosome 10, so these are distinct from the Lop (lens opacity) gene. Further studies of genetic linkage are needed to clarify whether lop-2 is responsible for both the 101/H and CBA/H cataracts.