bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical Genetics of the Cryptic Gene System for Cellobiose Utilization in Escherichia coli K12
Authors: Kricker Maja , Hall Barry G 
Published: January 2021

ABSTRACT
The cellobiose catabolic system of Escherichia coli K12 is being used to study the role of cryptic genes in microbial evolution. Wild-type E. coli K12 do not utilize the β-glucoside sugars, arbutin, salicin and cellobiose. A Cel+ (cellobiose utilizing) mutant which grows on cellobiose, arbutin, and salicin was isolated previously from wild-type E. coli K12. Biochemical assays indicate that a cel structural gene (celT) specifies a single transport protein that is a β-glucoside specific enzyme of the phosphoenolpyruvate-dependent phosphotransferase system. The transport protein phosphorylates β-glucosides at the expense of phosphoenolpyruvate. A single phosphoglucosidase, specified by celH, hydrolyzes phosphorylated cellobiose, arbutin, and salicin. The genes of the cel system are expressed constitutively in the Cel+ mutant, whereas they are not expressed at a detectable level in the wild-type strain. The transport and hydrolase genes are simultaneously silenced or simultaneously expressed and thus constitute an operon. Cel+ strains which fail to utilize one or more β-glucosides express the transport system at a lower level than do Cel+ strains which grow on all three β-glucosides. Other strains inducibly express a gene which specifies transport of arbutin but not the other β-glucosides. The arbutin transport gene, arbT, maps outside of the cel locus.
Repair of a Mismatch Is Influenced by the Base Composition of the Surrounding Nucleotide Sequence
Authors: Jones Madeleine , Wagner Robert , Radman Miroslav 
Published: January 2021

ABSTRACT
Heteroduplexes with single base pair mismatches of known sequence were prepared by annealing separated strands of bacteriophage λ DNA and used to transfect Escherichia coli. A series of transition (G:T and A:C) and transversion (G:A and C:T) mismatches located throughout most of the bacteriophage λ cI gene has been examined. The results suggest that the transition mismatches are generally better repaired than the transversion mismatches and that, at least for the transversion mismatches studied, repair efficiency increases with increasing G:C content in the neighboring nucleotide sequence. This specificity of the E. coli mismatch repair system can account, in part, for the similar frequencies of base substitution mutations throughout the E. coli genome.
Mating Type Linked Mutations Which Disrupt the Uniparental Transmission of Chloroplast Genes in Chlamydomonas
Authors: Gillham Nicholas W , Boynton John E , Johnson Anita M , Burkhart Bryce D 
Published: January 2021

ABSTRACT
In Chlamydomonas reinhardtii, chloroplast genomes are normally transmitted by the mating type plus (mt +) parent and mitochondrial genomes by the mating type minus (mt -) parent. In this paper we describe three new nuclear mutations, designated mat-3-1 to -3, which are tightly linked to the mt + allele and permit high transmission of chloroplast genomes from the mt - parent, but have no effect on transmission of mitochondrial genomes. We also show that mat-1, reported by others to be a nuclear mutation linked to mt - which promotes transmission of chloroplast genomes by the mt - parent, is probably a vegetative diploid since it contains both mt + and mt - alleles. Vegetative diploids behave as if they are mt - with respect to mating, but posses a level of chloroplast gene transmission intermediate between that of haploid mt - and mt + stocks.
A Test of Neutral Molecular Evolution Based on Nucleotide Data
Authors: Hudson Richard R , Kreitman Martin , Aguadé Montserrat 
Published: January 2021

ABSTRACT
The neutral theory of molecular evolution predicts that regions of the genome that evolve at high rates, as revealed by interspecific DNA sequence comparisons, will also exhibit high levels of polymorphism within species. We present here a conservative statistical test of this prediction based on a constant-rate neutral model. The test requires data from an interspecific comparison of at least two regions of the genome and data on levels of intraspecific polymorphism in the same regions from at least one species. The model is rejected for data from the region encompassing the Adh locus and the 5′ flanking sequence of Drosophila melanogaster and Drosophila sechellia. The data depart from the model in a direction that is consistent with the presence of balanced polymorphism in the coding region.
Sequence of the Structural Gene for Xanthine Dehydrogenase (rosy Locus) in Drosophila melanogaster
Authors: Keith Tim P , Riley Margaret A , Kreitman Martin , Lewontin R C , Curtis Daniel , Chambers Geoffrey 
Published: January 2021

ABSTRACT
We determined the nucleotide sequence of a 4.6-kb Eco RI fragment containing 70% of the rosy locus. In combination with information on the 5′ sequence, the gene has been sequenced in entirety. rosy cDNAs have been isolated and intron/exon boundaries have been determined. We find an open reading frame which spans four exons and would encode a protein of 1335 amino acids. The molecular weight of the encoded protein (xanthine dehydrogenase), based on the amino acid translation, is 146,898 daltons which agrees well with earlier biophysical estimates. Characteristics of the protein are discussed.
High Frequency Generalized Transduction by MiniMu Plasmid Phage
Authors: Wang Boamin , Liu Lin , Groisman Eduardo A , Casadaban Malcolm J , Berg Claire M 
Published: January 2021

ABSTRACT
Deletion derivatives of phage Mu which replicate as multicopy plasmids, and also transpose and package like Mu, have been developed for the in vivo cloning of bacterial genes. We show here that these miniMu plasmid phage are also efficient at generalized transduction and that both in vivo cloning and generalized transduction of a given gene can be accomplished in a single experiment.
Tests of the Double-Strand-Break Repair Model for Red-Mediated Recombination of Phage Λ and Plasmid Λdv
Authors: Thaler David S , Stahl Mary M , Stahl Franklin W 
Published: January 2021

ABSTRACT
The double-strand-break repair (DSBR) model was formulated to account for various aspects of yeast mitotic and meiotic recombination. In this study three features of the DSBR model are tested for Red-mediated recombination between phage λ and λdv, a plasmid that is perfectly homologous to about 10% of λ. The results support the applicability of the DSBR model to λ's Red system: (1) Creating a double-strand-break (DSB) within the region of homology shared by phage and plasmid increases their genetic interaction by about 20-fold. A DSB outside the region of shared homology has no such effect. (2) Both patches, i.e., simple marker rescue, and splices, i.e., co-integration of the phage and plasmid, are stimulated by a DSB in the region of shared homology. (3) Co-integrants harbor a duplication of the region of shared homology. Among co-integrants that were formed by the creation of a DSB, there is a preferential loss of whichever allele was in cis to a utilized cut site. The DSBR model as originally formulated involves the isomerization and cleavage of Holliday junctions to resolve the canonical intermediate. We propose as an alternative mechanism that a topoisomerase can resolve the canonical DSBR intermediate.
Analysis of the Promoter of the ninaE Opsin Gene in Drosophila melanogaster
Authors: Mismer Drzislav , Rubin Gerald M 
Published: January 2021

ABSTRACT
We have analyzed the cis-acting regulatory sequences of the ninaE gene. This gene encodes the major Drosophila melanogasteropsin, the protein component of the primary chromophore of photoreceptor cells R1-R6 of the adult eye. DNA fragments containing the start point of transcription of the ninaE gene were fused to either the Escherichia coli chloramphenicol acetyltransferase or lacZ (β-galactosidase) gene and introduced into the Drosophila germline by P-element-mediated transformation. Expression of the E. coli genes was then used to assay the ability of various sequences from the ninaE gene to confer the ninaE pattern of expression. Fragments containing between 2.8 kb and 215 bp of the sequences upstream of the start of transcription plus the first 67 bp of the untranslated leader were able to direct nearly wild-type expression. We have identified three separable control regions in the ninaE promoter. The first, which has the properties of an enhancer element, is located between nucleotides -501 and -219. The removal of this sequence had little effect on promoter function; this sequence appears to be redundant. However, it appears to be able to substitute for the second control region which is located between nucleotides -215 and -162, and which also affects the level of output from this promoter. Removal of these two control regions resulted in a 30-fold decrease in expression; however tissue specificity was not affected. The third control region, located downstream from nucleotide -120, appears to be absolutely necessary for promoter function in the absence of the first two regulatory sequences. Examination of larvae containing fusion genes expressing β-galactosidase suggests that the ninaE gene is also expressed in a subset of cells in the larval photoreceptor organ.
Genetic and Molecular Analysis of the Spm-dependent a-m2 Alleles of the Maize a Locus
Authors: Masson Patrick , Surosky Richard , Kingsbury Jeffrey A , Fedoroff Nina V 
Published: January 2021

ABSTRACT
The Suppressor-mutator (Spm) transposable element family of maize consists of the fully functional standard Spm (Spm-s) and many mutant elements. Insertion of an Spm element in or near a gene can markedly alter its expression, in some cases bringing the gene under the control of the mechanisms that regulate expression of the element. To gain insight into such mechanisms, as well as to enlarge our understanding of the Spm element's genetic organization, we have analyzed derivatives of a unique Spm insertion at the maize a locus in which the gene is co-expressed and co-regulated with the element. We describe the genetic properties and the structure of the a locus and Spm element in 9 strains (collectively designated the a-m2 alleles) selected by McClintock from the original a-m2 allele for heritable changes affecting either the Spm element or expression of the a gene. Most of the mutations are intra-element deletions within the 8.3-kb Spm element; many alter both Spm function and expression of the gene. Spm controls a gene expression in alleles with internally deleted, transposition-defective Spm elements and element ends contain the target sequences that mediate Spm's ability to activate expression of the gene. We argue that the properties of the a-m2 alleles reflect the operation of an element-encoded positive regulatory mechanism, as well as a negative regulatory mechanism that affects expression of the element, but appears not to be mediated by an element-encoded gene product.
Interactions Between Positive and Negative Regulators of GCN4 Controlling Gene Expression and Entry Into the Yeast Cell Cycle
Authors: Harashima Satoshi , Hannig Ernest M , Hinnebusch Alan G 
Published: January 2021

ABSTRACT
The GCN4 gene encodes a transcriptional activator in yeast whose expression is regulated at the translational level in response to amino acid availability. gcn3 mutations block derepression of GCN4 expression in starvation conditions. gcd1 and gcd12 mutations restore derepression of GCN4 expression in gcn3 deletion mutants, suggesting that GCN3 positively regulates GCN4 indirectly by antagonism of these GCD functions. gcd1 and gcd12 mutations also lead to temperature-sensitive arrest in the G1 phase of the cell cycle in gcn3 deletion mutants. The GCN3 allele completely suppresses both derepression of GCN4 expression and the temperature-sensitive growth conferred by gcd12 mutations and partially suppresses these phenotypes in gcd1 mutants. This suggests that the GCN3 product can promote or provide GCD function in nonstarvation conditions even though it opposes GCD function when cells are starved for amino acids. The gcn3-102 allele is completely defective for positive regulation of GCN4 expression; however, it mimics GCN3 in suppressing gcd1 and gcd12 mutations and thus retains the ability to restore GCD function in nonstarvation conditions. These data suggest that GCN3, GCD1 and GCD12 have closely related functions required for regulation of GCN4 expression and entry into the cell cycle. We suggest that GCN3 antagonizes the regulatory functions of GCD1 and GCD12 in starvation conditions either by competing with these factors for the same sites of action or by modifying their structures by physical interaction.
Drosophila Mitochondrial Genetics: Evolution of Heteroplasmy Through Germ Line Cell Divisions
Authors: Solignac Michel , Génermont Jean , Monnerot Monique , Mounolou Jean-Claude 
Published: January 2021

ABSTRACT
The mitochondrial genotype of all F1 female offspring (426 individuals) of a single Drosophila mauritiana female, heteroplasmic for two types of mtDNA (a short and a long genome), was established. All descendants were heteroplasmic. The earliest eggs laid by this female show the cytoplasmic genetic structure of ovariole stem cells at the end of development. Cohorts of females from the eggs laid day after day by this female, throughout the 31 days of its life, provide information on the evolution of the mitochondrial genotypes in the course of successive divisions of stem cells. An increase of the percentage of long DNA in offspring was observed as the female aged. Moreover, the variance of the genotypes increases as rounds of stem cell division progress. These results are supported by observations based on the adults issued from the early and late eggs, for three additional heteroplasmic females.
Partial revertants of the transposable element-associated suppressible allele white-apricot in Drosophila melanogaster: structures and responsiveness to genetic modifiers.
Authors: Mount S M , Green M M , Rubin G M 
Published: January 2021

Abstract
The eye color phenotype of white-apricot (wa), a mutant allele of the white locus caused by the insertion of the transposable element copia into a small intron, is suppressed by the extragenic suppressor suppressor-of-white-apricot (su(wa] and enhanced by the extragenic enhancers suppressor-of-forked su(f] and Enhancer-of-white-apricot (E(wa]. Derivatives of wa have been analyzed molecularly and genetically in order to correlate the structure of these derivatives with their response to modifiers. Derivatives in which the copia element is replaced precisely by a solo long terminal repeat (sLTR) were generated in vitro and returned to the germline by P-element mediated transformation; flies carrying this allele within a P transposon show a nearly wild-type phenotype and no response to either su(f) or su(wa). In addition, eleven partial phenotypic revertants of wa were analyzed. Of these, one appears to be a duplication of a large region which includes wa, three are new alleles of su(wa), two are sLTR derivatives whose properties confirm results obtained using transformation, and five are secondary insertions into the copia element within wa. One of these, waR84h, differs from wa by the insertion of the most 3' 83 nucleotides of the I factor. The five insertion derivatives show a variety of phenotypes and modes of interaction with su[f) and su(wa). The eye pigmentation of waR84h is affected by su(f) and E(wa), but not su(wa). These results demonstrate that copia (as opposed to the interruption of white sequences) is essential for the wa phenotype and its response to genetic modifiers, and that there are multiple mechanisms for the alteration of the wa phenotype by modifiers.
G-band position effects on meiotic synapsis and crossing over.
Authors: Ashley T 
Published: January 2021

Abstract
An examination of synaptic data from a series of X-autosome translocations and crossover data from an extensive series of autosome-autosome translocations and autosomal inversions in mice has lead to the development of a hypothesis which predicts synaptic and recombinational behavior of chromosomal aberrations during meiosis. This hypothesis predicts that in heterozygotes for chromosomal rearrangements that meiotically align G-light chromatin with G-light chromatin lack of homology will be recognized. If homologous synapsis cannot proceed, synaptonemal complex formation will cease and there will be no physical suppression of crossing over in such rearrangements. However, if a chromosomal rearrangement aligns G-light chromatin with G-dark chromatin at the time of synapsis, lack of homology will not be recognized and synaptonemal complex formation will proceed nonhomologously through the G-dark chromatin. Crossing over will be physically suppressed in this region and this suppression of crossing over will be confined to the chromosome in which the G-light chromatin is nonhomologously synapsed with G-dark chromatin. When G-light chromatin is once again aligned with G-light chromatin, lack of homology again will be recognized and either homologous synapsis will be reinitiated (as in an inversion loop), or will cease altogether (as in some translocations). Unlike the previously described "synaptic adjustment", this nonhomologous synapsis of G-light with G-dark chromatin appears to compete with homologous synapsis during early pachynema.
A stable genomic source of P element transposase in Drosophila melanogaster.
Authors: Robertson H M , Preston C R , Phillis R W , Johnson-Schlitz D M , Benz W K , Engels W R 
Published: January 2021

Abstract
A single P element insert in Drosophila melanogaster, called P[ry+ delta 2-3](99B), is described that caused mobilization of other elements at unusually high frequencies, yet is itself remarkably stable. Its transposase activity is higher than that of an entire P strain, but it rarely undergoes internal deletion, excision or transposition. This element was constructed by F. Laski, D. Rio and G. Rubin for other purposes, but we have found it to be useful for experiments involving P elements. We demonstrate that together with a chromosome bearing numerous nonautonomous elements it can be used for P element mutagenesis. It can also substitute efficiently for "helper" plasmids in P element mediated transformation, and can be used to move transformed elements around the genome.
Functional interactions of neurogenic genes of Drosophila melanogaster.
Authors: de-la-Concha A , Dietrich U , Weigel D , Campos-Ortega J A 
Published: January 2021

Abstract
The neurogenic genes of Drosophila melanogaster are involved in the decision of ectodermal cells to take on a neural or an epidermal fate. We present evidence in support of the notion that six of the neurogenic genes are functionally related. We studied the phenotype of embryos lacking one of the neurogenic genes in the presence of an increased dosage of the wild-type allele of another neurogenic gene. Our analysis also included the Hairless locus, whose function is related to that of the neurogenic genes, as well as to many other genes. The effects observed were asymmetric in that triploidy for a given gene modified the phenotype of loss of the function of another gene, but triploidy of the latter gene did not modify the phenotype of loss of the function of the former gene. These asymmetries allowed us to establish a polarity of gene interactions, as well as to order the genes according to the assumed ability of some of them to modify the activity of others. In this sequence, almondex is the first link and Enhancer of split the last one. Our evidence suggests that the function of big brain is independent of the function of the other six. The consequences of this arrangement for the commitment of ectodermal cells are discussed.
Spontaneous formation of compound X chromosomes in Drosophila melanogaster.
Authors: Morrison R J , Raymond J D , Zunt J R , Lim J K , Simmons M J 
Published: January 2021

Abstract
Males carrying different X chromosomes were tested for the ability to produce daughters with attached-X chromosomes. This ability is characteristic of males carrying an X chromosome derived from 59b-z, a multiply marked X chromosome, and is especially pronounced in males carrying the unstable 59b-z chromosomes Uc and Uc-lr. Recombination experiments with one of the Uc-lr chromosomes showed that the formation of compound chromosomes depends on two widely separated segments. One of these is proximal to the forked locus and is probably proximal to the carnation locus. This segment may contain the actual site of chromosome attachment. The other essential segment lies between the crossveinless and vermilion loci and may contain multiple factors that influence the attachment process.
Analysis of the mechanism for reversion of a disrupted gene.
Authors: Schiestl R H , Igarashi S , Hastings P J 
Published: January 2021

Abstract
A positive selection system for intrachromosomal recombination in Saccharomyces cerevisiae has been developed. This was achieved by integration of a plasmid containing an internal fragment of the HIS3 gene into its chromosomal location. This resulted in two copies of the HIS3 gene one with a terminal deletion at the 3' end and the other with a terminal deletion at the 5' end. Reversion of the gene disruption could be brought about by plasmid excision, unequal sister chromatid exchange or sister chromatid conversion. The purpose of this study was to define the mechanisms involved in reversion of the gene disruption. The frequency of plasmid excision could be determined by placing a yeast sequence bearing an origin of replication onto the plasmid that was subsequently integrated into the yeast genome. Unequal sister chromatid exchange and conversion could be distinguished by determining the nature of the reciprocal product by Southern blotting. The results indicate that reversion might occur mainly by conversion between sister chromatids. This is because the frequency of plasmid excision was about two orders of magnitude lower than the overall frequency of reversion and no reciprocal product indicative of sister chromatid exchange was found. The findings of this presentation suggest that conversion might be an important mechanism for recombination of sister chromatids and possibly for repair of damaged DNA in S or G2.
Genetic and physical analysis of the M26 recombination hotspot of Schizosaccharomyces pombe.
Authors: Ponticelli A S , Sena E P , Smith G R 
Published: January 2021

Abstract
The ade6-M26 mutation of Schizosaccharomyces pombe has previously been reported to stimulate ade6 intragenic meiotic recombination. We report here that the ade6-M26 mutation is a single G----T nucleotide change, that M26 stimulated recombination within ade6 but not at other distinct loci, and that M26 stimulated meiotic but not mitotic recombination. In addition, M26 stimulated recombination within ade6 when M26 is homozygous; this result demonstrates that a base-pair mismatch at the M26 site was not required for the stimulation. These results are consistent with the ade6-M26 mutation creating a meiotic recombination initiation site.