bluuebunny/crossref_metadata_2025_split huggingface dataset:
The comparative biology of second sex ratio evolution within a natural population of a parasitic wasp, Nasonia vitripennis.
Authors: Orzack S H 
Published: January 2021

Abstract
Correlation and regression analyses indicate that isofemale strains extracted from a population of the parasitic wasp, Nasonia vitripennis, differ in the fit of their second sex ratios (those produced in previously parasitized hosts) to the predictions of the theory of optimal facultative sex ratio adjustment. Under the theory's simple assumptions about population structure, there is significant heterogeneity of fitnesses among the isofemale strains. The reasons underlying these types of heterogeneity must be understood before we can make statements about the nature of sex ratio evolution in this species. These results suggest that comparative analyses are essential for testing the qualitative predictions of optimality models.
Determination of the inactivating alterations in two mutant alleles of the Neurospora crassa cross-pathway control gene cpc-1.
Authors: Paluh J L , Plamann M , Krüger D , Barthelmess I B , Yanofsky C , Perkins D D 
Published: January 2021

Abstract
cpc-1 is the locus specifying what is believed to be the major trans-activating transcription factor that regulates expression of amino acid biosynthetic genes subject to cross-pathway control in Neurospora crassa. Mutants altered at this locus are incapable of the global increase in gene expression normally seen in response to amino acid starvation. Using polymerase chain reaction methodology we have cloned and sequenced the inactive mutant allele, cpc-1 (CD15). The cpc-1 (CD15) mutation was found to be a single base pair deletion in codon 93 of the cpc-1 structural gene. A second, presumed lethal, allele, cpc-1 (j-5), also was investigated. Northern analyses with strains carrying the cpc-1 (j-5) allele revealed that no cpc-1 mRNA is produced. Southern and genetic analyses established that the cpc-1 (j-5) mutation involved a chromosomal rearrangement in which a break occurred within the cpc-1 locus, normally resident on linkage group VI; a small fragment from the left arm of linkage group VI, containing the cpc-1 promoter region and ylo-1, was translocated to the right arm of linkage group I. Other studies indicate that the cpc-1 locus itself is not essential for viability. Lethality previously attributed to the cpc-1 (j-5) mutation is due instead to the production of progeny that are deficient for essential genes in an adjoining segment of linkage group VI. Molecular characterization of cpc-1 (j-5) x ylo-1 pan-2 duplication progeny indicated that cpc-1 is normally transcribed towards the linkage group VI centromere.
The effects of chromosome rearrangements on the expression of heterochromatic genes in chromosome 2L of Drosophila melanogaster.
Authors: Wakimoto B T , Hearn M G 
Published: January 2021

Abstract
The light (lt) gene of Drosophila melanogaster is located at the base of the left arm of chromosome 2, within or very near centromeric heterochromatin (2Lh). Chromosome rearrangements that move the lt+ gene from its normal proximal position and place the gene in distal euchromatin result in mosaic or variegated expression of the gene. The cytogenetic and genetic properties of 17 lt-variegated rearrangements are described in this report. We show that five of the heterochromatic genes adjacent to lt are subject to inactivation by these rearrangements and that the euchromatic loci in proximal 2L are not detectably affected. The properties of the rearrangements suggest that proximity to heterochromatin is an important regulatory requirement for at least six 2Lh genes. We discuss how the properties of the position effects on heterochromatic genes relate to other proximity-dependent phenomena such as transvection.
GAL4 mutations that separate the transcriptional activation and GAL80-interactive functions of the yeast GAL4 protein.
Authors: Salmeron J M , Leuther K K , Johnston S A 
Published: January 2021

Abstract
The carboxy-terminal 28 amino acids of the Saccharomyces cerevisiae transcriptional activator protein GAL4 execute two functions--transcriptional activation and interaction with the negative regulatory protein, GAL80. Here we demonstrate that these two functions are separable by single amino acid changes within this region. We determined the sequences of four GAL4C-mutations, and characterized the abilities of the encoded GAL4C proteins to activate transcription of the galactose/melibiose regulon in the presence of GAL80 and superrepressible GAL80S alleles. One of the GAL4C mutations can be compensated by a specific GAL80S mutation, resulting in a wild-type phenotype. These results support the idea that while the GAL4 activation function tolerates at least minor alterations in the GAL4 carboxyl terminus, the GAL80-interactive function is highly sequence-specific and sensitive even to single amino acid alterations. They also argue that the GAL80S mutations affect the affinity of GAL80 for GAL4, and not the ability of GAL80 to bind inducer.
Break-join recombination in phage lambda.
Authors: Stahl F W , Fox M S , Faulds D , Stahl M M 
Published: January 2021

Abstract
In phage lambda, when DNA replication is blocked, recombination mediated by the Red pathway occurs only near the double-chain break site, cos, that defines the termini of the virion chromosome. The recombinants initiated by cos contain newly synthesized DNA near cos, in amount corresponding to a few percent of the length of lambda. A restriction enzyme cut delivered to one parent far from cos results in elevated recombination near the restriction site. Recombinants induced by this cut have a similarly small amount of DNA synthesis in these replication-blocked crosses. When restriction cuts are introduced in the presence of normal amounts of all of the DNA replication enzymes, many of the resulting recombinants still enjoy, at most, a small amount of DNA synthesis associated with the exchange event. Thus, these experiments fail to support the previously considered possibility that Red-mediated recombination in lambda proceeds largely through a break-copy pathway.
Centromeric regions control autonomous segregation tendencies in single-division meiosis of Saccharomyces cerevisiae.
Authors: Sharon G , Simchen G 
Published: January 2021

Abstract
We have previously shown that yeast cdc5 or cdc14 homozygotes can be led through a single-division meiosis in which some of the chromosomes segregate reductionally whereas others, within the same cell, segregate equationally. Chromosomes XI tend to segregate reductionally, whereas chromosomes IV tend to segregate equationally. In this report we present experiments with cdc5 homozygous strains, in which the centromeres of one or both chromosomes XI was replaced by the centromeric region from chromosome IV. Analysis of the products of single-division meioses in these strains demonstrates that the choice between reductional or equational segregation is directed by sequences in the vicinity of the centromeres. Although the choice is made separately for each individual chromosome, the analysis also reveals the existence of a system responsible for coordinated segregation of the two chromosomes of a given pair.
Genetic evidence that the ovo locus is involved in Drosophila germ line sex determination.
Authors: Oliver B , Pauli D , Mahowald A P 
Published: January 2021

Abstract
Zygotically contributed ovo gene product is required for the survival of female germ cells in Drosophila melanogaster. Trans-allelic combinations of weak and dominant ovo mutations (ovoD) result in viable germ cells that appear to be partially transformed from female to male sexual identity. The ovoD2 mutation is partially suppressed by many Sex-lethal alleles that affect the soma, while those that affect only the germ line fail to interact with ovoD2. One of two loss-of-function ovo alleles is suppressed by a loss-of-function Sex-lethal allele. Because ovo mutations are germ line dependent, it is likely that ovo is suppressed by way of communication between the somatic and germ lines. A loss-of-function allele of ovo is epistatic to germ line dependent mutations in Sex-lethal. The germ line dependent sex determination mutation, sans fille, and ovoD mutations show a dominant synergistic interaction resulting in partial transformation of germ line sexual identity. The ovo locus appears to be involved in germ line sex determination and is linked in some manner to sex determination in the soma.
Increased selection response in larger populations. I. Selection for wing-tip height in Drosophila melanogaster at three population sizes.
Authors: Weber K E 
Published: January 2021

Abstract
The effect of population size on selection response was investigated with replicated selection lines of 40, 200 and 1000 selected parents, using Drosophila melanogaster homozygous for the mutant raised. Selection for increased wing-tip height was carried out for 55 generations, with an average selection intensity of 0.6 standard deviation. The rank order of responses in the seven individual lines was significantly in order of population size, and the variance of response among lines showed a significant effect of population size. The final mean responses (selected - controls, +/- standard errors) in the three treatments, in order of increasing population size, were 8.6 +/- 1.8 mils (three small lines), 15.1 +/- 1.3 mils (two medium lines), and 19.8 +/- 1.5 mils (two large lines). The differences between treatments seem to have emerged too rapidly to be the result of mutations, and are probably due mainly to the utilization of existing variation with greater efficiency by selection in larger populations.
Intragenic suppression of a capsid assembly-defective P22 tailspike mutation.
Authors: Maurides P A , Schwarz J J , Berget P B 
Published: January 2021

Abstract
The tailspike protein of bacteriophage P22 assembles with mature capsids during the final reaction in phage morphogenesis. The gene 9 mutation hmH3034 synthesizes a tailspike protein with a change at amino acid 100 from Asp to Asn. This mutant form of trimeric tailspike protein fails to assemble with capsids in vivo. By using in vitro quantitative tailspike-capsid assembly assays, this mutant tailspike trimer can be shown to assemble with capsids at very high tailspike concentrations. From these assays, we estimate that this single missense mutation decreases by 100-500-fold the affinity of the tailspike for capsids. Furthermore, hmH3034 tailspike protein has a structural defect which makes the mature tailspike trimers sensitive to SDS at room temperature and causes the trimers to "partially unfold." Spontaneously arising intragenic suppressors of the capsid assembly defect have been isolated. All of these suppressors are changes at amino acid 13 of the tailspike protein, which substitute His, Leu or Ser for the wild type amino acid Arg. These hmH3034/sup3034 mutants and the separated sup3034 mutants form fully functional tailspike proteins with assembly activities indistinguishable from wild type while retaining the SDS-sensitive structural defect. From the analysis of the hmH3034 mutant and its suppressors, we propose that in the wild-type tailspike protein, the Asp residue at position 100 and the Arg residue at position 13 form an intrachain or interchain salt bridge which stabilizes the amino terminus of the tailspike protein and that the unneutralized positive charge at amino acid 13 in the hmH3034 protein is the cause of the assembly defect of this protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Structural genes for nitrate-inducible formate dehydrogenase in Escherichia coli K-12.
Authors: Berg B L , Stewart V 
Published: January 2021

Abstract
Formate oxidation coupled to nitrate reduction constitutes a major anaerobic respiratory pathway in Escherichia coli. This respiratory chain consists of formate dehydrogenase-N, quinone, and nitrate reductase. We have isolated a recombinant DNA clone that likely contains the structural genes, fdnGHI, for the three subunits of formate dehydrogenase-N. The fdnGHI clone produced proteins of 110, 32 and 20 kDa which correspond to the subunit sizes of purified formate dehydrogenase-N. Our analysis indicates that fdnGHI is organized as an operon. We mapped the fdn operon to 32 min on the E. coli genetic map, close to the genes for cryptic nitrate reductase (encoded by the narZ operon). Expression of phi(fdnG-lacZ) operon fusions was induced by anaerobiosis and nitrate. This induction required fnr+ and narL+, two regulatory genes whose products are also required for the anaerobic, nitrate-inducible activation of the nitrate reductase structural gene operon, narGHJI. We conclude that regulation of fdnGHI and narGHJI expression is mediated through common pathways.
Orientation of genes in the Bacillus subtilis chromosome.
Authors: Zeigler D R , Dean D H 
Published: January 2021

Abstract
The orientation of 96 genes on the Bacillus subtilis chromosome was deduced by the analysis of published data. Of these genes, 91 were found to be oriented so that their promoters were proximal to the chromosomal replication origin and their transcription termini to the replication terminus. Transcription of these genes would therefore be co-directional with replication. This chromosomal organization is consistent with the hypothesis advanced for Escherichia coli that bacteria avoid head-on collisions between RNA polymerase and DNA replication proteins by the appropriate orientation of their transcription units.
Mutations that affect transcription and cyclic AMP-CRP regulation of the adenylate cyclase gene (cya) of Salmonella typhimurium.
Authors: Fandl J P , Thorner L K , Artz S W 
Published: January 2021

Abstract
We studied the expression of the cya promoter(s) in cya-lac fusion strains of Salmonella typhimurium and demonstrated cAMP receptor protein (CRP)-dependent repression by cAMP. Expression of cya was reduced about fourfold in cultures grown in acetate minimal medium as compared to cultures grown in glucose-6-phosphate minimal medium. Expression of cya was also reduced about fourfold by addition of 5 mM cAMP to cultures grown in glucose minimal medium. We constructed in vitro deletion and insertion mutations altering a major cya promoter (P2) and a putative CRP binding site overlapping P2. These mutations were recombined into the chromosome by allele replacement with M13mp::cya recombinant phages and the regulation of the mutant promoters was analyzed. A 4-bp deletion of the CRP binding site and a 4-bp insertion in this site nearly eliminated repression by cAMP. A mutant with the P2 promoter and the CRP binding site both deleted exhibited an 80% reduction in cya expression; the 20% residual expression was insensitive to cAMP repression. This mutant retained a Cya+ phenotype. Taken together, the results establish that the cya gene is transcribed from multiple promoters one of which, P2, is negatively regulated by the cAMP-CRP complex. Correction for the contribution to transcription by the cAMP-CRP nonregulated cya promoters indicates that the P2 promoter is repressed at least eightfold by cAMP-CRP.
The unusual spectrum of mutations induced by hybrid dysgenesis at the Triplo-lethal locus of Drosophila melanogaster.
Authors: Dorer D R , Christensen A C 
Published: January 2021

Abstract
The Triplo-lethal locus (Tpl) is unique in its dosage sensitivity; no other locus in Drosophila has been identified that is lethal when present in three doses. Tpl is also haplo-lethal, and its function is still a mystery. Previous workers have found it nearly impossible to mutationally inactive Tpl other than by completely deleting the chromosomal region in which Tpl resides (83DE). We have utilized P-M hybrid dysgenesis in an effort to obtain new mutations of Tpl. We recovered 19 new duplications of Tpl, 15 hypomorphic mutations of Tpl (a previously rare class of mutation), and no null mutations. Surprisingly, 14 of the 15 hypomorphic alleles have no detectable P element sequences at the locus. The difficulty in recovering null mutations in Tpl suggests that it may be a complex locus, perhaps consisting of several genes with redundant functions. The relative ease with which we recovered hypomorphic alleles is in sharp contrast to previous attempts by others to mutagenize Tpl. A higher mutation rate with hybrid dysgenesis than with radiation or chemicals also suggests a peculiar genetic organization for the locus.
A simple method for estimating average number of nucleotide substitutions within and between populations from restriction data.
Authors: Nei M , Miller J C 
Published: January 2021

Abstract
A simple method is proposed for estimating the average number of nucleotide substitutions per site within and between populations for the case where a large number of individuals are examined for many restriction enzymes. This method gives essentially the same results as those obtained by Nei and Li's method but saves a large amount of computer time. The variances of the quantities estimated can be obtained by the jackknife method, and these variances are very similar to those obtained by Nei and Jin's more sophisticated method. A similar method can also be applied to DNA sequence data.
Developmental genetic analysis of Contrabithorax mutations in Drosophila melanogaster.
Authors: González-Gaitán M A , Micol J L , García-Bellido A 
Published: January 2021

Abstract
A developmental analysis of the Contrabithorax (Cbx) alleles offers the opportunity to examine the role of the Ultrabithorax (Ubx) gene in controlling haltere, as alternative to wing, morphogenesis in Drosophila. Several Cbx alleles are known with different spatial specificity in their wing toward haltere homeotic transformation. The molecular data on these mutations, however, does not readily explain differences among mutant phenotypes. In this work, we have analyzed the "apogenetic" mosaic spots of transformation in their adult phenotype, in mitotic recombination clones and in the spatial distribution of Ubx proteins in imaginal discs. The results suggest that the phenotypes emerge from early clonality in some Cbx alleles, and from cell-cell interactions leading to recruitment of cells to Ubx gene expression in others. We have found, in addition, mutual interactions between haltere and wing territories in pattern and dorsoventral symmetries, suggesting short distance influences, "accommodation," during cell proliferation of the anlage. These findings are considered in an attempt to explain allele specificity in molecular and developmental terms.
Spontaneous point mutations that occur more often when advantageous than when neutral.
Authors: Hall B G 
Published: January 2021

Abstract
Recent reports have called into question the widespread belief "that mutations arise continuously and without any consideration for their utility" (in the words of J. Cairns) and have suggested that some mutations (which Cairns called "directed" mutations) may occur as specific responses to environmental challenges, i.e., they may occur more often when advantageous than when neutral. In this paper it is shown that point mutations in the trp operon reverted to trp+ more frequently under conditions of prolonged tryptophan deprivation when the reversions were advantageous, than in the presence of tryptophan when the reversions were neutral. The overall mutation rate, as determined from the rates of mutation to valine resistance and to constitutive expression of the lac operon, did not increase during tryptophan starvation. The trp reversion rate did not increase when the cells were starved for cysteine for a similar period, indicating that the increased reversion rate was specific to conditions where the reversions were advantageous. Two artifactual explanations for the observations, delayed growth of some preexisting revertants and cryptic growth by some cells at the expense of dying cells within aged colonies, were tested and rejected as unlikely. The trp+ reversions that occurred while trp- colonies aged in the absence of tryptophan were shown to be time-dependent rather than replication-dependent, and it is suggested that they occur by mechanisms different from those that have been studied in growing cells. A heuristic model for the molecular basis of such mutations is proposed and evidence consistent with that model is discussed. It is suggested that the results in this and previous studies can be explained on the basis of underlying random mechanisms that act during prolonged periods of physiological stress, and that "directed" mutations are not necessarily the basis of those observations.
Insertional inactivation and cloning of the wA gene of Aspergillus nidulans.
Authors: Tilburn J , Roussel F , Scazzocchio C 
Published: January 2021

Abstract
We describe examples of wA gene inactivation (resulting in white conidiospores) obtained during transformation of Aspergillus nidulans. One wA- transformant was obtained by transformation with a prn+ plasmid of a strain with green conidia (wA+) which was unable to catabolize L-proline (prn-). This transformant contains a very large number of plasmid copies integrated at a single site inseparable from the wA locus. Passage of this transformant through the sexual cycle generated a variety of novel phenotypes for L-proline utilization, the number and frequency of which depended upon the cleistothecium from which the progeny were obtained, suggesting that the altered phenotypes were due to premeiotic events. The most extreme phenotype was severe hypersensitivity to L-proline. Hypersensitive progeny had a much reduced number of integrated plasmid copies enabling us to identify and clone putative prn-wA fusion sequences and subsequently retrieve wA sequences from a wild-type gene library. One of the wild-type clones overlapped the different sites of the insertional mutations in two wA- transformants and complemented the wA3 allele. Sequences within this clone hybridized to a transcript that was developmentally regulated in the wild type and absent in a number of mutants defective in conidiospore development. A reiterated sequence was also found in the region of the wA gene.
The genetics of a small autosomal region of Drosophila melanogaster containing the structural gene for alcohol dehydrogenase. VII. Characterization of the region around the snail and cactus loci.
Authors: Ashburner M , Thompson P , Roote J , Lasko P F , Grau Y , el Messal M , Roth S , Simpson P 
Published: January 2021

Abstract
The genetic interval 35C to 36A on chromosome arm 2L of Drosophila melanogaster has been saturated for mutations with visible or lethal phenotypes. 38 loci have been characterized, including several maternal-effect lethals (vasa, Bic-C, chiffon, cactus and cornichon) and several early embryonic lethals, including snail and fizzy. About 130 deletions have been used to order these loci. Complex interactions between mutant alleles have been uncovered in the immediate genetic environs of the snail gene, as has further evidence for an interaction between this region and that including the nearby genes no-ocelli and elbow.