bluuebunny/crossref_metadata_2025_split huggingface dataset:
Whole-Genome Comparisons of Ergot Fungi Reveals the Divergence and Evolution of Species within the Genus Claviceps Are the Result of Varying Mechanisms Driving Genome Evolution and Host Range Expansion
Authors: Wyka Stephen A , Mondo Stephen J , Liu Miao , Dettman Jeremy , Nalam Vamsi , Broders Kirk D 
Published: January 2021

Abstract
The genus Claviceps has been known for centuries as an economically important fungal genus for pharmacology and agricultural research. Only recently have researchers begun to unravel the evolutionary history of the genus, with origins in South America and classification of four distinct sections through ecological, morphological, and metabolic features (Claviceps sects. Citrinae, Paspalorum, Pusillae, and Claviceps). The first three sections are additionally characterized by narrow host range, whereas section Claviceps is considered evolutionarily more successful and adaptable as it has the largest host range and biogeographical distribution. However, the reasons for this success and adaptability remain unclear. Our study elucidates factors influencing adaptability by sequencing and annotating 50 Claviceps genomes, representing 21 species, for a comprehensive comparison of genome architecture and plasticity in relation to host range potential. Our results show the trajectory from specialized genomes (sects. Citrinae and Paspalorum) toward adaptive genomes (sects. Pusillae and Claviceps) through colocalization of transposable elements around predicted effectors and a putative loss of repeat-induced point mutation resulting in unconstrained tandem gene duplication coinciding with increased host range potential and speciation. Alterations of genomic architecture and plasticity can substantially influence and shape the evolutionary trajectory of fungal pathogens and their adaptability. Furthermore, our study provides a large increase in available genomic resources to propel future studies of Claviceps in pharmacology and agricultural research, as well as, research into deeper understanding of the evolution of adaptable plant pathogens.
DEFECTIVE HISTONE TRANSITION DURING SPERMIOGENESIS IN HETEROZYGOUS SEGREGATION DISTORTER MALES OF DROSOPHILA MELANOGASTER
Authors: Hauschteck-Jungen Elizabeth , Hartl Daniel L 
Published: January 2021

ABSTRACT
Males of Drosophila melanogaster that are heterozygous for the segregation distorter (SD) chromosome produce a gross excess of SD-bearing offspring because most of the non-SD-bearing sperm are dysfunctional. These dysfunctional sperm exhibit abnormalities in chromatin condensation and compaction during spermiogenesis. Use of the fluorescent dye sulfoflavine, which is specific for basic proteins, has now revealed that the dysfunctional sperm are also defective in the normal transition from somatic to spermatid-specific histones.
INTERACTIONS BETWEEN FUSED AND ENGRAILED, TWO MUTATIONS AFFECTING PATTERN FORMATION IN DROSOPHILA MELANOGASTER
Authors: Fausto-Sterling Anne , Smith-Schiess Heidi 
Published: January 2021

ABSTRACT
In this paper we demonstrate that the severity of the engrailed phenotype is greatly increased when engrailed is combined with the X-linked mutation fused. The secondary sex combs of fu;en flies contain from two to four times more setae than do those of en siblings. The number of transverse rows of bristles on the metatarsus of the metathoracic leg is reduced by a factor of one and a half to two in fu;en flies when compared to their en siblings, while the frequency of reversed bract polarity, bristle abnormalities and misshapen metatarsi increases greatly. In addition, fu;en flies express the en wing phenotype more completely than their siblings and have a much higher frequency of wing vein abnormalities—some of which we have interpreted as triplications of the third and first longitudinal wing veins. We briefly discuss the significance of the fused-engrailed gene interaction.
ON THE CONTROL OF THE DISTRIBUTION OF MEIOTIC EXCHANGE IN DROSOPHILA MELANOGASTER
Authors: Carpenter Adelaide T C , Baker Bruce S 
Published: January 2021

ABSTRACT
The effects of eight recombination-defective meiotic mutants on crossing over within the X heterochromatin were examined. Since none permit substantial frequencies of exchange within heterochromatin although six lessen or abolish constraints on the location of exchanges within euchromatin, the systems that prohibit exchange within heterochromatin and that govern where exchanges will occur in euchromatin are under separate genetic control.—A minor component of the effects of mei-218 is the production of nonhomologous exchanges; of mei-9 is the recovery of deleted chromatids; and of mei-41 is the recovery of deleted chromatids and/or a low frequency of heterochromatic exchanges.
UNEXPECTED BEHAVIOR IN TWO LOCUS GENETIC SYSTEMS: AN ANALYSIS OF MARGINAL UNDERDOMINANCE AT A STABLE EQUILIBRIUM
Authors: Hastings Alan 
Published: January 2021

ABSTRACT
The phenomenon of marginal underdominance at a stable equilibrium in a two-locus-two-allele deterministic selection model is studied analytically using bifurcation theory. This technique and additional numerical studies indicate several new aspects of the phenomenon that are of biological importance. Marginal underdominance can occur at both loci simultaneously and can be present in a model with small fitness differentials. This can occur for a fitness scheme that is a one parameter generalization of the classical symmetric fitness model.
POLYCOMBLIKE: A GENE THAT APPEARS TO BE REQUIRED FOR THE NORMAL EXPRESSION OF THE BITHORAX AND ANTENNAPEDIA GENE COMPLEXES OF DROSOPHILA MELANOGASTER
Authors: Duncan Ian McKenzie 
Published: January 2021

ABSTRACT
A newly identified gene is described that is required for the maintenance of normal identities in many of the body segments of the fly. The effects of mutants in this gene, which is called Polycomblike (Pcl), suggest that its wild-type allele functions in the regulation of the bithorax gene complex (BX-C) and the Antennapedia gene complex (ANT-C). Evidence in favor of this idea derives from (1) the close correspondence between segmental transformations caused by Pcl mutants and those caused by dominant gain-of-function mutants in the BX-C and ANT-C, (2) the interactions observed between Pcl mutants and mutants in these complexes, and (3) the dependence upon BX-C and ANT-C dosage of the severity of at least one of the transformations caused by Pcl mutants. Arguments are presented that the control of the BX-C and ANT-C by Pcl + is negative in nature. The results of clonal analysis experiments indicate that, at least for the BX-C, Pcl + exerts this control until late in development. Since the wild-type allele of another gene, called Polycomb (Pc), has previously been shown to have many of the same properties as Pcl +, it appears that the BX-C and perhaps also the ANT-C are continuously regulated during development by at least two and probably several other genes.
LOCALIZATION OF MINUTES TO SPECIFIC POLYTENE CHROMOSOME BANDS BY MEANS OF OVERLAPPING DUPLICATIONS
Authors: Broderick David J , Roberts Paul A 
Published: January 2021

ABSTRACT
Overlapping duplications recovered as suppressors of Minute loci have been used to localize M(2)z and M(3)w 124 to specific polytene bands 25A1(2) and 95A1(2). The surprising efficiency of M localization by duplication may result from the tendency of M suppressors to be at least a visible fraction of a polytene band in length.
PROPERTIES AND EVOLUTIONARY POTENTIAL OF NEWLY INDUCED TANDEM DUPLICATIONS IN DROSOPHILA MELANOGASTER
Authors: Roberts Paul A , Broderick David J 
Published: January 2021

ABSTRACT
Most of some 33 X-ray-induced duplications recovered as Suppressors of Minute loci proved to be direct tandem duplications. When heterozygous, most duplications were crossover suppressors, and duplications of short to moderate size did not reduce the fitness of their bearers. Crossover suppression by tandem duplication may be attributed to intrastrand foldbacks of the type regularly seen in somatic polytene chromosomes. As a consequence, linkage disequilibrium between duplicated elements and normal chromosomes should be more profound than has been supposed. Tandem duplications appear to be predisposed by reason of frequency of generation, crossover suppression and fitness effects to serve as the primary source of new genes.
STUDIES ON THE SEX-SPECIFIC LETHALS OF DROSOPHILA MELANOGASTER. V. SEX TRANSFORMATION CAUSED BY INTERACTIONS BETWEEN A FEMALE-SPECIFIC LETHAL, Sxl
f#1, AND THE MALE-SPECIFIC LETHALS mle(3)132, msl-2
27, AND mle
Authors: Uenoyama T , Fukunaga A , Ioshi K 
Published: January 2021

ABSTRACT
Interactions between a female-specific lethal mutant, Sxlf #1, and each of three male-specific lethal mutants, mle(3)132, msl-2 27 and mle, of Drosophila melanogaster were observed to produce morphological changes in various sexually dimorphic external characters. Chromosomal females heterozygous for Sxlf #1 and homozygous for any one of the male-specific lethals (and to a lesser degree heterozygous for male-specific lethals) sometimes had sex combs, male-type tergites, male-type sternites, male-type anal plates or male-type external genitalia. Penetrance was not high and expression was often incomplete; single individuals never had all the sexually dimorphic structures transformed. When mothers were homozygous for male-specific lethals, higher proportions of female progeny were affected than when mothers were heterozygous, suggesting a maternal effect.
THE REX GENE OF BACTERIOPHAGE λ IS REALLY TWO GENES
Authors: Matz Karen , Schmandt Margaret , Gussin Gary N 
Published: January 2021

ABSTRACT
Complementation tests among previously isolated rex - mutants of bacteriophage λ reveal that the mutants comprise two complementation groups, designated rexA and rexB. Because rexB - mutants complement prm - mutants, but rexA - mutants do not, it appears that the rexA gene is coordinately controlled with the cI (repressor) gene under the direction of the PRM promoter, but that some other promoter is capable of directing the expression of rexB.
SELECTION FOR THE α-THALASSEMIA GENES
Authors: Yokoyama Shozo 
Published: January 2021

ABSTRACT
Extremely high incidences of single and double deletions of α-globin genes are known among Asian populations. To study possible mechanisms for the maintenance of such deletions, mathematical analyses have been conducted. It has been shown that a stable polymorphism can be achieved easily through heterozygote advantage using deterministic models. The results strongly suggest that high incidences of single and double deletion of α-globin genes among Asian populations are maintained by some type of heterozygote advantage.
VIABILITY OF FEMALE GERM-LINE CELLS HOMOZYGOUS FOR ZYGOTIC LETHALS IN DROSOPHILA MELANOGASTER
Authors: Garcia-Bellido Antonio , Robbins Leonard G 
Published: January 2021

ABSTRACT
We have analyzed the viability of different types of X chromosomes in homozygous clones of female germ cells. The chromosomes carried viable mutations, single-cistron zygotic-lethal and semi-lethal mutations, or small (about six chromosome band) deletions. Homozygous germ-line clones were produced by recombination in females heterozygous for an X-linked, dominant, agametic female sterile.
All the zygotic-viable mutants are also viable in germ cells. Of 16 deletions tested (uncovering a total of 93 bands) only 2 (of 4 and 5 bands) are germ-cell viable. Mutations in 15 lethal complementation groups in the zeste-white region were tested. When known, the most extreme alleles at each locus were tested. Only in five loci (33%) were the mutants viable in the germ line. Similar studies of the same deletions and point-mutant lethals in epidermal cells show that 42% of the bands and 77% of the lethal alleles are viable. Thus, germ-line cells have more stringent cell-autonomous genetic requirements than do epidermal cells.
The eggs recovered from clones of three of the germ-cell viable zw mutations gave embryos arrested early in embryogenesis, although genotypically identical embryos derived from heterozygous oogonia die as larvae or even hatch as adult escapers. For two genes, homozygosis of the mutations tested also caused embryonic arrest of heterozygous female embryos, and in one case, the eggs did not develop at all. Germ-line clones of one quite leaky mutation gave eggs that were indistinguishable from normal. The abundance of genes whose products are required for oogenesis, whose products are required in the oocyte, and whose activity is required during zygotic development is discussed.
LINKAGE MODIFICATION WITH MIXED RANDOM MATING AND SELFING: A NUMERICAL STUDY
Authors: Holsinger Kent E , Feldman Marcus W 
Published: January 2021

ABSTRACT
Although recombination cannot increase under conditions of random mating or complete selfing in regimes of constant selection, with mixed random mating and selfing, selection for increased recombination can occur. For some fitness regimes there may be selection for reduced recombination with both low and high degrees of selfing but selection for increased recombination with moderate degrees of selfing. With some fitness regimes there is a historical effect: depending on which equilibrium a population starts from, there may be selection for either increased or decreased recombination. In other cases the direction of selection may be determined by the present state of individuals within the population. If recombination is already fairly limited, there may be selection for further reduction. If recombination is already fairly frequent, there may be selection for increased recombination. For certain symmetric viability systems there may be an intermediate value of the recombination fraction between 0 and 0.5 toward which the population will evolve. Although it is not yet possible to classify precisely those fitness matrices that can exhibit selection for increased recombination, it does appear that selection for increased recombination can occur only if at least two of the double homozygotes are less fit than would be expected on the basis of a comparison of the fitnesses of the single and double heterozygotes on an additive scale.
ON THE COMPONENTS OF SEGREGATION DISTORTION IN DROSOPHILA MELANOGASTER. II. DELETION MAPPING AND DOSAGE ANALYSIS OF THE SD LOCUS
Authors: Brittnacher John G , Ganetzky Barry 
Published: January 2021

ABSTRACT
Segregation distorter (SD) chromosomes are preferentially transmitted to offspring from heterozygous SD/SD + males owing to the induced dysfunction of the SD +-bearing sperm. This phenomenon involves at least two major loci: the Sd locus whose presence is necessary for distortion to occur and the Rsp locus which acts as the site of Sd action. Several additional loci on SD chromosomes enhance distortion.—In a previous study deletions were used to map the Sd locus and to determine some of its properties. We have extended this analysis with the isolation and characterization of 14 new deletions in the Sd region. From our results we conclude (1) SD chromosomes contain a single Sd locus located in region 37D2-6 of the salivary gland chromosome map. Deletion of this locus in any of three SD chromosomes now studied results in complete loss of ability to distort a sensitive chromosome; (2) the reduced male fecundity observed in many homozygous SD or SDi/SDj combinations is due at least in part to the action of the Sd locus. The fecundity of these males can be substantially increased by deletion of one Sd locus. Thus, it is the presence of two doses of Sd rather than the absence of Sd + that produces the lowered male fecundity in SD homozygotes; (3) Sd behaves as a neomorph, whereas Sd +, if it exists at all, is amorphic with respect to segregation distortion; (4) these results support a model in which the Sd product is made in limiting amounts and the interaction of this product with the Rsp locus causes sperm dysfunction. The Sd product appears to act preferentially at Rsps (sensitive-Responder) but may also act at Rspi (insensitive-Responder).
ADAPTATION AT SPECIFIC LOCI. II. DEMOGRAPHIC AND BIOCHEMICAL ELEMENTS IN THE MAINTENANCE OF THE COLIAS PGI POLYMORPHISM
Authors: Watt Ward B 
Published: January 2021

ABSTRACT
Demographically oriented sampling in the wild and biochemical study of allozymes in the laboratory have been used to probe maintenance of the phosphoglucose isomerase polymorphism of Colias butterflies.—The several alleles at this locus show negative or no covariation among their frequencies in the wild. This rules out Wahlund effects as a cause of observations of heterozygote excess at this locus in broods that fly as single cohorts. Unusually heavy mortality among adults, due to drought stress or other causes, can preclude manifestation of differential survivorship among phosphoglucose isomerase genotypes. In broods composed of overlapping cohorts, heterozygote deficiency, apparently due to Wahlund effects in time as cohorts of different survivorship experience mix, can be found. Heterozygotes at this locus fly under a broader range of weather conditions than other genotypes.—Previously detected kinetic differentiation among the genotypes extends in greater magnitude to the glycolytic reaction direction, as well as to a broader range of test conditions than examined before. The heterozygote 3/4 is strikingly heterotic for several measures of kinetic functional effectiveness. Other heterozygotes are sometimes heterotic, more often intermediate (but not exactly so, nor additive in any sense) in properties between homozygotes.—Predictions are made from the biochemical analysis and from the insects' thermal ecology concerning distributions of the genotypes in the wild. Some agree with facts already established. Others are tested and confirmed from data already on hand. Still others are to be tested as reported in an accompanying paper.—All available evidence points to a combination of heterozygote advantage and fluctuating-environment selection as responsible for maintaining this polymorphism. There is considerable evidence for the operation of protein-structural constraint on the range of adaptations possible at this locus.
ISOLATION AND CHARACTERIZATION OF LIGHT-INSENSITIVE MUTANTS OF NEUROSPORA CRASSA
Authors: Paietta John , Sargent Malcolm L 
Published: January 2021

ABSTRACT
As part of a genetic analysis of blue light photoreception in Neurospora, three mutants were isolated that do not exhibit photosuppression of circadian conidiation, i.e., they show periodic conidiation in constant light. The mutations have been given the designations lis-1, lis-2 and lis-3 ("light insensitive"). The three mutations segregate as single nuclear genes, are nonallelic and are recessive to wild type in heterokaryon tests. The linkage groups of the mutations are as follows: lis-1, I; lis-2, VI; and lis-3, V. The light -insensitive phenotype of the mutants is restricted to the photosuppression response; other responses such as photoinduced phase shifting of the conidiation rhythm and photoinduced carotenogenesis are not altered. The physiological or biochemical defects of the mutants have not been established, but they are not similar to previous reported cases (i.e., rib and poky) in which a reduction in light sensitivity has been observed.
SHOULD INDIVIDUAL FITNESS INCREASE WITH HETEROZYGOSITY?
Authors: Turelli Michael , Ginzburg Lev R 
Published: January 2021

ABSTRACT
Natural selection influences not only gamete frequencies in populations but also the multilocus fitness structures associated with segregating gametes. In particular, only certain patterns of multilocus fitnesses are consistent with the maintenance of stable multilocus polymorphisms. This paper offers support for the proposition that, at stable, viability-maintained, multilocus polymorphisms, the fitness of a genotype tends to increase with the number of heterozygous loci it contains. Average fitness always increases with heterozygosity at stable product equilibria (i.e., those without linkage disequilibrium) maintained by either additive or multiplicative fitness schemes. Simulations suggest that it "generally" increases for arbitrary fitness schemes. The empirical literature correlating allozyme heterozygosity with fitness-correlated traits is discussed in the light of these and other theoretical results.
THE EFFECT OF mei-41 ON rDNA REDUNDANCY IN DROSOPHILA MELANOGASTER
Authors: Hawley R Scott , Tartof Kenneth D 
Published: January 2021

ABSTRACT
The recombination and repair defective mutant, mei-41, exhibits three rather striking effects on the genetic properties and chromosomal stability of rDNA in Drosophila. First, mei-41 inhibits rDNA magnification. However, mei-9, another recombination and repair defective mutation has no similar effect. This indicates that magnification requires some, but not all, of the gene products necessary for meiotic exchange. Second, under magnifying conditions, mei-41 induces interchanges between the X rDNA and either arm of the Ybb - chromosome. These interchanges occur at high frequency and are independent of rDNA orientation. Third, in mei-41 bb +/Ybb + males, bobbed mutants in the X, but not the Y, also arise at high frequency. Evidence suggests that these events involve the rDNA type I insertion. The recombination and repair defective properties of mei-41 together with our results regarding its unusual and specific effects involving rDNA are explained in a simple model that has general implications for chromosome structure.
TRANSPOSABLE ELEMENTS IN MENDELIAN POPULATIONS. I. A THEORY
Authors: Langley Charles H , Brookfield John F Y , Kaplan Norman 
Published: January 2021

ABSTRACT
Transposable elements are DNA sequences, found throughout eukaryotes, that transpose replicatively and cause numerous genetic and developmental effects on their hosts. A model of the evolution of transposable elements in Mendelian populations is proposed. From its analysis, formulas for the mean copy number and frequency spectrum are obtained.
FREQUENCY DISTRIBUTION OF ESTERASE-5 ALLELES IN TWO POPULATIONS OF DROSOPHILA PSEUDOOBSCURA
Authors: Keith Tim Perri 
Published: January 2021

ABSTRACT
Statistical tests comparing allele frequencies in natural populations with those predicted by various theories of genic variation depend critically on the accurate enumeration of alleles. This study used a series of five sequential electrophoretic conditions to characterize the allele frequency distributions of esterase-5 in two large population samples of Drosophila pseudoobscura from California. In Standard chromosome lines 12 electromorphs were discriminated using a single electrophoretic condition. When four additional criteria were used, the number of electromorphs increased to 41, 33 in one population and 22 in the other. Both populations had the same two alleles in high frequency, with other alleles present in frequencies of 6% or less. Although each population had a number of unique alleles, a χ2 contingency test demonstrated no significant genetic divergence between them. A statistical comparison of allele frequencies in both populations with that predicted by neutral models suggests that the individual and combined distributions deviate from neutrality in the direction of purifying selection.—Sex-Ratio chromosomes differed markedly from Standard chromosomes in both allelic content and diversity. In 32 Sex-Ratio chromosomes from one population only three alleles were found, all of which were detected under the initial "standard" electrophoretic conditions. Moreover, none of these alleles was found in the Standard chromosome lines.