bluuebunny/crossref_metadata_2025_split huggingface dataset:
deltex, a locus interacting with the neurogenic genes, Notch, Delta and mastermind in Drosophila melanogaster.
Authors: Xu T , Artavanis-Tsakonas S 
Published: January 2021

Abstract
The Notch locus of Drosophila melanogaster, which codes for a transmembrane protein sharing homology with the mammalian epidermal growth factor, is one of a small number of zygotically acting genes, the so called neurogenic loci, which are necessary for the correct segregation of neural from epidermal lineages during embryogenesis. In an attempt to identify genes whose products may interact with that of Notch, we designed a genetic screen aimed at identifying suppressors of certain Notch mutations which are known to affect the extracellular epidermal growth factor homologous domain of Notch. Mutations in two neurogenic loci were identified as suppressors: Delta, whose product was recently shown to interact with Notch and mastermind. In addition, a third, X-linked gene was shown capable of acting as a suppressor. We show that this gene is the deltex locus, characterize the phenotype of deltex mutations, and demonstrate both a maternal and zygotic action of the locus. All deltex alleles behave as recessive viables affecting wing, ocellar and eye morphology. There are allele specific interactions between deltex and various Notch alleles; for example, deltex mutants with a reduced dosage of wild-type Notch die as pupae. deltex also interacts with Delta and mastermind in a fashion that is formally analogous to its interaction with Notch. These results emphasize the special relationship between Notch, Delta and mastermind suggested by previous work and indicate that deltex is likely to play an important role in the same genetic circuitry within which these three neurogenic loci operate.
Homology of melanoma-inducing loci in the genus Xiphophorus.
Authors: Schartl M 
Published: January 2021

Abstract
Several species of the genus Xiphophorus are polymorphic for specific pigment patterns. Some of these give rise to malignant melanoma following the appropriate crossings. For one of these pattern loci from the playfish Xiphophorus maculatus the melanoma-inducing gene has been cloned and found to encode a novel receptor tyrosine kinase, designated Xmrk. Using molecular probes from this gene in Southern blot analyses on single fish DNA preparations from 600 specimens of different populations of various species of the genus Xiphophorus and their hybrids, either with or without melanoma-predisposing pattern, it was shown that all individuals contain the Xmrk gene as a proto-oncogene. It is located on the sex chromosome. All fish that carry a melanoma-predisposing locus which has been identified by Mendelian genetics contain an additional copy of Xmrk, closely linked to a specific melanophore pattern locus on the sex chromosome. The melanoma-inducing loci of the different species and populations are homologous. The additional copy of Xmrk obviously arose by a gene-duplication event, thereby acquiring the oncogenic potential. The homology of the melanoma-inducing loci points to a similar mechanism of tumor suppression in all feral fish populations of the different species of the genus Xiphophorus.
kem mutations affect nuclear fusion in Saccharomyces cerevisiae.
Authors: Kim J , Ljungdahl P O , Fink G R 
Published: January 2021

Abstract
We have identified mutations in three genes of Saccharomyces cerevisiae, KEM1, KEM2 and KEM3, that enhance the nuclear fusion defect of kar1-1 yeast during conjugation. The KEM1 and KEM3 genes are located on the left arm of chromosome VII. Kem mutations reduce nuclear fusion whether the kem and the kar1-1 mutations are in the same or in different parents (i.e., in both kem kar1-1 X wild-type and kem X kar 1-1 crosses). kem 1 X kem 1 crosses show a defect in nuclear fusion, but kem 1 X wild-type crosses do not. Mutant kem 1 strains are hypersensitive to benomyl, lose chromosomes at a rate 10-20-fold higher than KEM+ strains, and lose viability upon nitrogen starvation. In addition, kem 1/kem 1 diploids are unable to sporulate. Cells containing a kem 1 null allele grow very poorly, have an elongated rod-shape and are defective in spindle pole body duplication and/or separation. The KEM 1 gene, which is expressed as a 5.5-kb mRNA transcript, contains a 4.6-kb open reading frame encoding a 175-kD protein.
The let-60 locus controls the switch between vulval and nonvulval cell fates in Caenorhabditis elegans.
Authors: Han M , Aroian R V , Sternberg P W 
Published: January 2021

Abstract
During induction of the Caenorhabditis elegans hermaphrodite vulva by the anchor cell of the gonad, six multipotent vulval precursor cells (VPCs) have two distinct fates: three VPCs generate the vulva and the other three VPCs generate nonspecialized hypodermis. Genes that control the fates of the VPCs in response to the anchor cell signal are defined by mutations that cause all six VPCs to generate vulval tissue (Multivulva or Muv) or that cause all six VPCs to generate hypodermis (Vulvaless or Vul). Seven dominant Vul mutations were isolated as dominant suppressors of a lin-15 Muv mutation. These mutations are dominant alleles of the gene let-60, previously identified only by recessive lethal mutations. Our genetic studies of these dominant Vul recessive lethal mutations, recessive lethal mutations, intragenic revertants of the dominant Vul mutations, and the closely mapping semi-dominant multivulva lin-34 mutations suggest that: (1) loss-of-function mutations of let-60 are recessive lethal at a larval stage, but they also cause a Vul phenotype if the lethality is rescued maternally by a lin-34 gain-of-function mutation. (2) The dominant Vul alleles of let-60 are dominant negative mutations whose gene products compete with wild-type activity. (3) lin-34 semidominant Muv alleles are either gain-of-function mutations of let-60 or gain-of-function mutations of an intimately related gene that elevates let-60 activity. We propose that let-60 activity controls VPC fates. In a wild-type animal, reception by a VPC of inductive signal activates let-60, and it generates into a vulval cell type; in absence of inductive signal, let-60 activity is low and the VPC generates hypodermal cells. Our genetic interaction studies suggest that let-60 acts downstream of let-23 and lin-15 and upstream of lin-1 and lin-12 in the genetic pathway specifying the switch between vulval and nonvulval cell types.
Increased variation in ADH enzyme activity in Drosophila mutation-accumulation experiment is not due to transposable elements at the Adh structural gene.
Authors: Aquadro C F , Tachida H , Langley C H , Harada K , Mukai T 
Published: January 2021

Abstract
We present here a molecular analysis of the region surrounding the structural gene encoding alcohol dehydrogenase (Adh) in 47 lines of Drosophila melanogaster that have each accumulated mutations for 300 generations. While these lines show a significant increase in variation of alcohol dehydrogenase enzyme activity compared to control lines, we found no restriction map variation in a 13-kb region including the complete Adh structural gene and roughly 5 kb of both 5' and 3' sequences. Thus, the rapid accumulation of ADH activity variation after 28,200 allele generations does not appear to have been due to the mobilization of transposable elements into or out of the Adh structural gene region.
Genetic analysis of B-Peru, a regulatory gene in maize.
Authors: Patterson G I , Harris L J , Walbot V , Chandler V L 
Published: January 2021

Abstract
The B locus in maize is required for the accumulation of anthocyanin pigments. Numerous B alleles have been described: each determines a particular pattern of pigment synthesis with respect to the tissues that are pigmented and the time during development that pigment synthesis begins. We report here a genetic analysis of one B allele, B-Peru, which regulates synthesis of pigments in both kernel and plant tissues. We used stocks with active Mutator transposable elements to produce eight mutations in B-Peru. All eight alter pigment synthesis in all the kernel and plant tissues pigmented by B-Peru, suggesting that each mutation has disrupted a region of the gene required for expression in all tissues. Six of the mutations cause a colorless phenotype, while two cause a reduction in pigment in both kernel and plant tissues. Four of the mutations are unstable, and four are stable upon self-pollination. Multiple independent revertants were isolated from each unstable allele. DNA blot analysis demonstrated that all eight mutants are the result of insertions within an approximately 5-kb region that encodes the B-Peru transcript. One of the four unstable alleles contains a Mu element, Mu1.7. Two others contain insertions related to the Spm family of transposable elements. Thus, our Mutator stocks also contained active transposable elements from the unrelated Spm family. Our experiments suggest that the B-Peru allele is not complex, but contains a single coding region that regulates pigment synthesis in multiple tissues.
Magnaporthe grisea genes for pathogenicity and virulence identified through a series of backcrosses.
Authors: Valent B , Farrall L , Chumley F G 
Published: January 2021

Abstract
We have identified genes for pathogenicity toward rice (Oryza sativa) and genes for virulence toward specific rice cultivars in the plant pathogenic fungus Magnaporthe grisea. A genetic cross was conducted between the weeping lovegrass (Eragrostis curvula) pathogen 4091-5-8, a highly fertile, hermaphroditic laboratory strain, and the rice pathogen O-135, a poorly fertile, female-sterile field isolate that infects weeping lovegrass as well as rice. A six-generation backcrossing scheme was then undertaken with the rice pathogen as the recurrent parent. One goal of these crosses was to generate rice pathogenic progeny with the high fertility characteristic of strain 4091-5-8, which would permit rigorous genetic analysis of rice pathogens. Therefore, progeny strains to be used as parents for backcross generations were chosen only on the basis of fertility. The ratios of pathogenic to nonpathogenic (and virulent to avirulent) progeny through the backcross generations suggested that the starting parent strains differ in two types of genes that control the ability to infect rice. First, they differ by polygenic factors that determine the extent of lesion development achieved by those progeny that infect rice. These genes do not appear to play a role in infection of weeping lovegrass because both parents and all progeny infect weeping lovegrass. Second, the parents differ by simple Mendelian determinants, "avirulence genes," that govern virulence toward specific rice cultivars in all-or-none fashion. Several crosses confirm the segregation of three unlinked avirulence genes, Avr 1-CO39, Avr 1-M201 and Avr1-YAMO, alleles of which determine avirulence on rice cultivars CO39, M201, and Yashiro-mochi, respectively. Interestingly, avirulence alleles of Avr1-CO39, Avr1-M201 and Avr1-YAMO were inherited from the parent strain 4091-5-8, which is a nonpathogen of rice. Middle repetitive DNA sequences ("MGR sequences"), present in approximately 40-50 copies in the genome of the rice pathogen parent, and in very low copy number in the genome of the nonpathogen of rice, were used as physical markers to monitor restoration of the rice pathogen genetic background during introgression of fertility. The introgression of highest levels of fertility into the most successful rice pathogen progeny was incomplete by the sixth generation, perhaps a consequence of genetic linkage between genes for fertility and genes for rice pathogenicity. One chromosomal DNA segment with MGR sequence homology appeared to be linked to the gene Avr1-CO39. Finally, many of the crosses described in this paper exhibited a characteristic common to many crosses involving M. grisea rice pathogen field isolates.(ABSTRACT TRUNCATED AT 400 WORDS)
Molecular analysis of Saccharomyces cerevisiae chromosome I: identification of additional transcribed regions and demonstration that some encode essential functions.
Authors: Diehl B E , Pringle J R 
Published: January 2021

Abstract
Saccharomyces cerevisiae chromosome I has provided a vivid example of the "gene-number paradox." Although molecular studies have suggested that there are greater than 100 transcribed regions on the chromosome, classical genetic studies have identified only about 15 genes, including just 6 identified in intensive studies using Ts- lethal mutations. To help elucidate the reasons for this disparity, we have undertaken a detailed molecular analysis of a 34-kb segment of the left arm of the chromosome. This segment contains the four known genes CDC24, WHI1, CYC3 and PYK1 plus at least seven transcribed regions of unknown function. The 11 identified transcripts have a total length of approximately 25.9 kb, suggesting that greater than or equal to 75% of the DNA in this region is transcribed. Of the transcribed regions of unknown function, three are essential for viability on rich medium and three appear to be nonessential, as judged by the lethality or nonlethality of deletions constructed using integrative transformation methods. No obvious phenotypes were associated with the deletions in the apparently nonessential genes. However, two of these genes may have homologs elsewhere in the genome, as judged from the appearance of additional bands when DNA-DNA blot hybridizations were performed at reduced stringency. Taken together, the results provide further evidence that the limitations of classical genetic studies of chromosome I cannot be explained solely by a lack of genes, or even a lack of essential genes, on the chromosome.
Inferences of species phylogeny in relation to segregation of ancient polymorphisms.
Authors: Wu C I 
Published: January 2021

Abstract
Standard formulas of gene frequency change under genetic drift are used to derive the probability of obtaining incorrect phylogenetic information for three species due to segregation of ancient polymorphisms. This probability depends upon the level of polymorphisms at the time of speciation and is generally quite high unless the two speciation events are far apart in time. If phylogenetic data from multiple loci are available, a likelihood ratio test can be used to reject the null hypothesis in favor of the best phylogeny. The appropriate null hypothesis is either a trichotomy or an alternative phylogeny, depending on the data set. The likelihood ratios required for accepting the best phylogeny are given. These ratios are obtained by exact enumeration when the number of loci is small (n less than 15) and by an asymptotic approach for larger n's. In general, more than five loci are needed to resolve the species phylogeny.
Changes in relative fitness with temperature among second chromosome arrangements in Drosophila melanogaster.
Authors: van Delden W , Kamping A 
Published: January 2021

Abstract
Development time and body weight of In(2L)t, R (a putative short inversion on the left arm of the second chromosome) and ST (standard) karyotypes of Drosophila melanogaster were measured at different temperatures. Frequency changes were followed in populations polymorphic for In(2L)t and ST and kept under different environmental conditions. These experiments were carried out in order to explain the worldwide latitudinal clines for In(2L)t and other inversions. To avoid interactions with the Adh and alpha Gpdh loci, which also have latitudinal clines, all karyotypes were homozygous AdhS alpha GpdhF. In(2L)t homokaryotypes had a longer development time and a lower weight than the other karyotypes at all temperatures. R/ST heterokaryotypes had the shortest development time and ST/ST had the smallest weight decrease with increasing temperature. The differences among the In(2L)t and ST karyotypes in development time were further analyzed in an experiment where the age at which 50% of the larvae were able to become adults, without further food ingestion, was determined. In polymorphic populations at 20 degrees and 25 degrees a significant decline of In(2L)t frequencies was observed. At 29.5 degrees and 33 degrees there was no change in In(2L)t frequencies but a significant excess of heterokaryotypes occurred. On ethanol-supplemented food the most drastic decline in In(2L)t frequency was observed. Populations transferred at 2- and 3-week intervals at 25 degrees exhibited large differences in final In(2L)t frequencies. The frequency changes could in part be attributed to the differences in development time and to previously observed differences in high temperature resistance. The experiments prove that the karyotypes are under selection. The results are discussed in relation to the geographic distribution of In(2L)t.
The comparative biology of genetic variation for conditional sex ratio behavior in a parasitic wasp, Nasonia vitripennis.
Authors: Orzack S H , Parker E D , Gladstone J 
Published: January 2021

Abstract
Using genetic markers, we tracked the sex ratio behavior of individual females of the parasitic wasp, Nasonia vitripennis, in foundress groups of size 1, 2, 4, 8 and 16. Comparison of 12 isofemale strains extracted from a natural population reveals significant between-strain heterogeneity of sex ratios produced in all sizes of foundress group. Under simple assumptions about population structure, this heterogeneity results in heterogeneity of fitnesses. The strains differ in their conditional sex ratio behavior (the sex ratio response of a female to foundress groups of different sizes). Females of some strains produce more males as foundress group size increases (up to size eight). Females of another strain produce more males when not alone but do not respond differentially to group size otherwise. Females of two other strains show no conditional sex ratio behavior. Females of only two strains behave differently in foundress groups of size 8 and 16. Correlation and regression analyses indicate that the strains differ significantly in their fit to the predictions of an evolutionarily stable strategy (ESS) model of conditional sex ratio behavior. Such heterogeneity contradicts the notion that females of this species possess conditonal sex ratio behavior that is optimal in the ESS sense. The results imply that this ESS model is useful but not sufficient for understanding the causal basis of the evolution of this behavior in this species. This is the first report on the sex ratio behavior of individual females in multiple foundress groups in any species of parasitic wasp. Data of this type (and not foundress group or "patch" sex ratios) are essential for testing evolutionary models that predict the sex ratio behaviors of individuals. We suggest that a test for an ESS model include the answers to two important questions: 1) is the model quantitatively accurate? and 2) is there reasonable evidence to indicate that natural selection has caused individuals to manifest the ESS behavior?
FST in a hierarchical island model.
Authors: Slatkin M , Voelm L 
Published: January 2021

Abstract
It is shown that in a hierarchical island model, in which demes within a neighborhood exchange migrants at a much higher rate than do demes in different neighborhoods, hierarchical F statistics introduced by S. Wright can indicate the extent of gene flow within and between neighborhoods. At equilibrium, the within-neighborhood inbreeding coefficient, FSN, is approximately 1/(1 + 4Nm1) where N is the deme size and m1 is the migration rate among demes in the same neighborhood. The between-neighborhood inbreeding coefficient, FNT, is approximately 1/(1 + 4Ndm2) where d is the number of demes in a neighborhood and m2 is the migration rate among demes in different neighborhoods.
Quantitative genetics of postponed aging in Drosophila melanogaster. II. Analysis of selected lines.
Authors: Hutchinson E W , Shaw A J , Rose M R 
Published: January 2021

Abstract
Quantitative genetic analyses of Drosophila melanogaster stocks with postponed aging have suffered from the problem of a lack of certainty concerning patterns of allelic differentiation. The present experiments were designed to alleviate this difficulty by selecting for enhanced levels of characters known to be related to postponed aging. Selection successfully increased the degree of differentiation of postponed aging stocks with respect to starvation resistance and fecundity, but persistent additive genetic variance suggested that selection did not result in fixation of alleles. The artificially selected stocks were subjected to crosses to test for patterns of dominance and maternal effects. There was little evidence for these effects in the inheritance of the characters underlying postponed aging, even with the increased differentiation of the selected stocks.
A superfamily of Arabidopsis thaliana retrotransposons.
Authors: Konieczny A , Voytas D F , Cummings M P , Ausubel F M 
Published: January 2021

Abstract
We describe a superfamily of Arabidopsis thaliana retrotransposable elements that consists of at least ten related families designated Ta1-Ta10. The Ta1 family has been described previously. Two genomic clones representing the Ta2 and Ta3 elements were isolated from an A. thaliana (race Landsberg erecta) lambda library using sequences derived from the reverse transcriptase region of Ta1 as hybridization probes. Nucleotide sequence analysis showed that the Ta1, Ta2 and Ta3 families share greater than 75% amino acid identity in pairwise comparisons of their reverse transcriptase and RNase H genes. In addition to Ta1, Ta2 and Ta3, we identified seven other related retrotransposon families in Landsberg erecta, Ta4-Ta10, using degenerate primers and the polymerase chain reaction to amplify a highly conserved region of retrotransposon-encoded reverse transcriptase. One to two copies of elements Ta2-Ta10 are present in the genomes of the A. thaliana races Landsberg erecta and Columbia indicating that the superfamily comprises at least 0.1% of the A. thaliana genome. The nucleotide sequences of the reverse transcriptase regions of the ten element families place them in the category of copia-like retrotransposons and phylogenetic analysis of the amino acid sequences suggests that horizontal transfer may have played a role in their evolution.