bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and High-Density Mapping of Gene-Rich Regions in Chromosome Group 5 of Wheat
Authors: Gill Kulvinder S , Gill Bikram S , Endo Takashi R , Boyko Elena V 
Published: January 2021

Abstract
The distribution of genes and recombination in the wheat genome was studied by comparing physical maps with the genetic linkage maps. The physical maps were generated by mapping 80 DNA and two phenotypic markers on an array of 65 deletion lines for homoeologous group 5 chromosomes. The genetic maps were constructed for chromosome 5B in wheat and 50 in Triticum tauschii. No marker mapped in the proximal 20% chromosome region surrounding the centromere. More than 60% of the long arm markers were present in three major clusters that physically encompassed &lt;18% of the arm. Because 48% of the markers were cDNA clones and the distributions of the cDNA and genomic clones were similar, the marker distribution may represent the distribution of genes. The gene clusters were identified and allocated to very small chromosome regions because of a higher number of deletions in their surrounding regions. The recombination was suppressed in the centromeric regions and mainly occurred in the gene-rich regions. The bp/cM estimates varied from 118 kb for gene-rich regions to 22 Mb for gene-poor regions. The wheat genes present in these clusters are, therefore, amenable to molecular manipulations parallel to the plants with smaller genomes like rice.
Destabilization of Simple Repetitive DNA Sequences by Transcription in Yeast
Authors: Wierdl Monika , Greene Christopher N , Datta Abhijit , Jinks-Robertson Sue , Petes Thomas D 
Published: January 2021

Abstract
Simple repetitive DNA sequences in the eukaryotic genome frequently alter in length. In wild-type strains, we find that transcription through a repetitive poly GT tract destabilizes the tract four- to ninefold. In mismatch repair-deficient yeast strains, simple repeats are very unstable. High levels of transcription in such strains destabilize repetitive tracts an additional two- to threefold.
Pseudohomothallism and Evolution of the Mating-Type Chromosome in Neurospora tetrasperma
Authors: Merino Sandra T , Nelson Mary Anne , Jacobson David J , Natvig Donald O 
Published: January 2021

Abstract
Ascospores of Neurospora tetrasperma normally contain nuclei of both mating-type idiomorphs (a and A), resulting in self-fertile heterokaryons (a type of sexual reproduction termed pseudohomothallism). Occasional homokaryotic self-sterile strains (either a or A) behave as heterothallics and, in principle, provide N. tetrasperma with a means for facultative outcrossing. This studywas conceived as an investigation of the population biology of N. tetrasperma to assess levels of intrastrain heterokaryosis (heterozygosity). The unexpected result was that the mating-type chromosome and autosomes exhibited very different patterns of evolution, apparently because of suppressed recombination between mating-type chromosomes. Analysis of sequences on the mating-type chromosomes of wild-collected self-fertile strains revealed high levels of genetic variability between sibling A and a nuclei. In contrast, sequences on autosomes of sibling A and a nuclei exhibited nearly complete homogeneity. Conservation of distinct haplotype combinations on A and a mating-type chromosomes in strains from diverse locations further suggested an absence of recombination over substantial periods of evolutionary time. The suppression of recombination on the N. tetrasperma mating-type chromosome, expected to ensure a high frequency of self fertility, presents an interesting parallel with, and possible model for studying aspects of, the evolution of mammalian sex chromosomes.
Mutations in the Drosophila melanogaster Gene Encoding S-adenosylmethionine Suppress Position-Effect Variegation
Authors: Larsson Jan , Zhang Jingpu , Rasmuson-Lestander Åsa 
Published: January 2021

Abstract
In Drosophila melanogaster, the study of trans-acting modifier mutations of position-effect variegation and Polycomb group (Pc-G) genes have been useful tools to investigate genes involved in chromatin structure. We have cloned a modifier gene, Suppesssm of zeste 5 (Su(z)5), which encodes Sadenosylmethionine synthetase, and we present here molecular results and data concerning its expression in mutants and genetic interactions. The mutant alleles Su(z)5, l(2)R23 and l(2)M6 show suppression of wm4 and also of two white mutants induced by roo element insertions in the regulatory region i.e., wis (in combination with z 1) and wsp1. Two of the Su(z)S alleles, as well as a deletion of the gene, also act as enhancers of PoZycomb by increasing the size of sex combs on midleg. The results suggest that Su(z)5 is connected with regulation of chromatin structure. The enzyme Sadenosylmethionine synthetase is involved in the synthesis of Sadenosylmethionine, a methyl group donor and also, after decarboxylation, a propylamino group donor in the bio-synthesis of polyamines. Our results from HPLC analysis show that in ovaries from heterozygous Su(z)5 mutants the content of spermine is significantly reduced. Results presented here suggest that polyamines are an important molecule class in the regulation of chromatin structure.
Integrated Genetic Map of Anopheles gambiae: Use of RAPD Polymorphisms for Genetic, Cytogenetic and STS Landmarks
Authors: Dimopoulos George , Zheng Liangbiao , Kumar Vasantha , della Torre Alessandra , Kafatos Fotis C , Louis Christos 
Published: January 2021

Abstract
Randomly amplified polymorphic DNA (RAPD) markers have been integrated in the genetic and cytogenetic maps of the malaria vector mosquito, Anopheles gambiae. Fifteen of these markers were mapped by recombination, relative to microsatellite markers that had been mapped previously. Thirty-four gel-purified RAPD bands were cloned and sequenced, generating sequence tagged sites (STSs) that can be used as entry points to the A. gambiae genome. Thirty one of these STSs were localized on nurse cell polytene chromosomes through their unique hybridization signal in in situ hybridization experiments. Five STSs map close to the breakpoints of polymorphic inversions, which are notable features of the Anopheles genome. The usefulness and limitations of this integrated mosquito map are discussed.
Isolation of Arabidopsis Mutants With Enhanced Disease Susceptibility by Direct Screening
Authors: Glazebrook Jane , Rogers Elizabeth E , Ausubel Frederick M 
Published: January 2021

Abstract
To discover which components of plant defense responses make significant contributions to limiting pathogen attack, we screened a mutagenized population of Arabidopsis thalzana for individuals that exhibit increased susceptibility to the moderately virulent bacterial pathogen Pseudomonas syringae pv. maculicola ES4326 (Psm ES4326). The 12 enhanced disease susceptibility (eds) mutants isolated included alleles of two genes involved in phytoalexin biosynthesis (pad2, which had been identified previously, and pad4, which had not been identified previously), two alleles of the previously identified npr1 gene, which affects expression of other defense genes, and alleles of seven previously unidentified genes of unknown function. The npr-1 mutations caused greatly reduced expression of the PRI gene in response to PsmES4326 infection, but had little effect on expression of two other defense genes, BGL2 and PR5, suggesting that PR1 expression may be important for limiting growth of PsmES4326. While direct screens for mutants with quantitative pathogen-susceptibility phenotypes have not been reported previously, our finding that mutants isolated in this way include those affected in known defense responses supports the notion that this type of screening strategy allows genetic dissection of the roles of various plant defense responses in disease resistance.
Fine-Structure Mapping of Meiosis-Specific Double-Strand DNA Breaks at a Recombination Hotspot Associated With an Insertion of Telomeric Sequences Upstream of the HIS4 Locus in Yeast
Authors: Xu Fei , Petes Thomas D 
Published: January 2021

Abstract
Meiotic recombination in Saccharomyces cerevisiae is initiated by double-strand DNA breaks (DSBs). Using two approaches, we mapped the position of DSBs associated with a recombination hotspot created by insertion of telomeric sequences into the region upstream of HIS4. We found that the breaks have no obvious sequence specificity and localize to a region of ~50 bp adjacent to the telomeric insertion. By mapping the breaks and by studies of the exonuclease III sensitivity of the broken ends, we conclude that most of the broken DNA molecules have blunt ends with 3′-hydroxyl groups.
Mismatch Repair Mutants in Yeast Are Not Defective in Transcription-Coupled DNA Repair of UV-Induced DNA Damage
Authors: Sweder Kevin S , Verhage Richard A , Crowley David J , Crouse Gray F , Brouwer Jaap , Hanawalt Philip C 
Published: January 2021

Abstract
Transcription-coupled repair, the targeted repair of the transcribed strands of active genes, is defective in bacteria, yeast, and human cells carrying mutations in mfd, RAD26 and ERCC6, respectively. Other factors probably are also uniquely involved in transcription-repair coupling. Recently, a defect was described in transcription-coupled repair for Escherichia coli mismatch repair mutants and human tumor cell lines with mutations in mismatch repair genes. We examined removal of UV-induced DNA damage in yeast strains mutated in mismatch repair genes in an effort to confirm a defect in transcription-coupled repair in this system. In addition, we determined the contribution of the mismatch repair gene MSH2 to transcription-coupled repair in the absence of global genomic repair using rad7Δ mutants. We also determined whether the Rad26-independent transcription-coupled repair observed in rad26Δ and rad7Δ rad26Δ mutants depends on MSH2 by examining repair deficiencies of rad26Δ msh2Δ and rad7Δ rad26Δ msh2Δ mutants. We found no defects in transcription-coupled repair caused by mutations in the mismatch repair genes MSH2, MLH1, PMS1, and MSH3. Yeast appears to differ from bacteria and human cells in the capacity for transcription-coupled repair in a mismatch repair mutant background.
Mosaic Analysis Using a ncl-1 (+) Extrachromosomal Array Reveals That lin-31 Acts in the Pn.p Cells During Caenorhabditis elegans Vulval Development
Authors: Miller Leilani M , Waxing David A , Kim Stuart K 
Published: January 2021

Abstract
We describe a genetic mosaic analysis procedure in which Caenorhabditis elegans mosaics are generated by spontaneous loss of an extrachromosomal array. This technique allows almost any C. elegans gene that can be used in germline transformation experiments to be used in mosaic analysis experiments. We identified a cosmid clone that rescues the mutant phenotype of ncl-1, so that this cell-autonomous marker could be used to analyze mosaic animals. To determine the sites of action for unc-29 and lin-31, an extrachromosomal array was constructed containing the ncl-1(+) cosmid linked to lin-31(+) and unc-29(+) cosmids. This array is mitotically unstable and can be lost to produce a clone of mutant cells. The specific cell division at which the extrachromosomal array had been lost was deduced by scoring the Ncl phenotypes of individual cells in genetic mosaics. The Unc-29 and Lin-31 phenotypes were then scored in these animals to determine in which cells these genes are required. This analysis showed that unc-29, which encodes a subunit of the acetylcholine receptor, acts in the body muscle cells. Furthermore, lin-31, which specifies cell fates during vulval induction and encodes a putative transcription factor similar to HNF-3/fork head, acts in the Pn.p cells
A Genetic Pathway Conferring Life Extension and Resistance to UV Stress in Caenorhabditis elegans
Authors: Murakami Shin , Johnson Thomas E 
Published: January 2021

Abstract
A variety of mechanisms have been proposed to explain the extension of adult life span (Age) seen in several mutants in Caenorhabditis elegans (age-1: an altered aging rate; daf-2 and daf-23 activation of a dauer-specific longevity program; spe-26: reduced fertility; ck-1: an altered biological clock). Using an assay for ultraviolet (UV) resistance in young adult hermaphrodites (survival after UV irradiation), we observed that all these Age mutants show increased resistance to UV. Moreover, mutations in daf-16 suppressed the UV resistance as well as the increased longevity of all the Age mutants. In contrast to the multiple mechanisms initially proposed, these results suggest that a single, daf-16dependent pathway, specifies both extended life span and increased UV resistance. The mutations in daf-16 did not alter the reduced fertility of spe-26and interestingly a daf-16mutant is more fertile than wild type. We propose that life span and some aspects of stress resistance are jointly negatively regulated by a set of gerontogenes (genes whose alteration causes life extension) in C. elegans.
Identification and Genetic Analysis of wunen, a Gene Guiding Drosophila melanogaster Germ Cell Migration
Authors: Zhang Nian , Zhang Jiaping , Cheng Yan , Howard Ken 
Published: January 2021

Abstract
We describe a novel genetic locus, wunen (wun), required for guidance of germ cell migration in early Drosophila development. Loss of wun function does not abolish movement but disrupts the orientation of the motion causing the germ cells to disperse even though their normal target, the somatic gonad, is well formed. We demonstrate that the product of this gene enables a signal to pass from the soma to the germ line and propose that the function of this signal is to selectively stabilize certain cytoplasmic extensions resulting in oriented movement. To characterize this guidance factor, we have mapped wun to within 100 kb of cloned DNA.
Scalloped wings Is the Lucilia cuprina Notch Homologue and a Candidate for the Modifier of Fitness and Asymmetry of Diazinon Resistance
Authors: Davies Andrew G , Game Anne Y , Chen Zhenzhong , Williams Tracey J , Goodall Stephen , Yen Janet L , McKenzie John A , Batterham Philip 
Published: January 2021

Abstract
The Scalloped wings (Scl) gene of the Australian sheep blowfly, Lucilia cuprina, is shown to be the homologue of the Drosophila melanogaster Notch gene by comparison at the DNA sequence and genetic levels. A L. cuprina genomic fragment, which shows strong identity with the Notch (N) gene at the molecular level, hybridizes to the location of the Scl gene on polytene chromosomes. The two genes are functionally homologous; the dominant and recessive Notch-like phenotypes produced by mutations in the Scl gene allow these alleles to be classed as N-like or Abruptex-like. The Scl gene is under investigation as a candidate for the fitness and asymmetry Modifier (M) of diazinon resistance. We show that M affects the penetrance of wing and bristle phenotypes associated with two Scl alleles in a manner consistent with the M being an allele of Scl. In addition, we report a phenotypic interaction between the diazinon-resistance mutation, Rop-1, and the same alleles of Scl. We propose that the product of Rop-1, an esterase, may be involved in cell adhesion in developmental processes involving the Scl gene product.
Degree of Selective Constraint as an Explanation of the Different Rates of Evolution of Gender-Specific Mitochondrial DNA Lineages in the Mussel Mytilus
Authors: Stewart Donald T , Kenchington Ellen R , Singh Rama K , Zouros Eleftherios 
Published: January 2021

Abstract
Mussels of the genus Mytilus segregate for a maternally transmitted F lineage and a paternally transmitted M lineage of mitochondrial DNA. Previous studies demonstrated that these lineages are older than the species of the M. edulis complex and that the M lineage evolves faster than the F lineage. Here we show that the latter observation also applies to a region of the molecule with no assigned function. Sequence data for the mitochondrial COIII gene and the “unassigned” region of the F and M lineages of M. edulis and M. trossulus are used to evaluate various hypotheses that may account for the faster rate of evolution of the M lineage. Tests based on the proportion of synonymous and nonsynonymous substitutions suggest that the M lineage experiences relatively relaxed selection. Further support for this hypothesis comes from an examination of COIII amino acid substitutions at sites defined as either conserved or variable based on the pattern of variation in other mollusks and Drosophila. Most substitutions in the M lineage occur in regions that are also variable among non-Mytilus taxa. We suggest that these differences in selection pressure are a consequence of doubly uniparental mitochondrial DNA transmission in Mytilus.
Sex and the Spread of Retrotransposon Ty3 in Experimental Populations of Saccharomyces cerevisiae
Authors: Zeyl Clifford , Bell Graham , Green David M 
Published: January 2021

Abstract
Mobile genetic elements may be molecular parasites that reduce the fitness of individuals that bear them by causing predominantly deleterious mutations, but increase in frequency when rare because transposition increases their rates of transmission to the progeny of crosses between infected and uninfected individuals. If this is true, then the initial spread of a mobile element requires sex. We tested this prediction using the yeast retrotransposon Ty3 and a strain of Saccharomyces cerevisiae lacking Ty3. We infected replicate isogenic sexual and asexual populations with a galactose-inducible Ty3 element at an initial frequency of 1%. In two of six asexual populations, active Ty3 elements increased in frequency to 38 and 86%, due to the spread in each population of a competitively superior mutant carrying a new Ty3 insertion. Ty3 frequencies increased above 80% in all sexual populations in which transposition was induced in haplophase or in diplophase. Ty3 did not increase in frequency when active during both haplophase and diplophase, apparently because of selective sweeps during adaptation to galactose. Repressed Ty3 elements spread in sexual populations, by increasing sexual fitness. These results indicate that active Ty3 elements are more likely to become established in sexual populations than in asexual populations.
The Prevention of Repeat-Associated Deletions in Saccharomyces cerevisiae by Mismatch Repair Depends on Size and Origin of Deletions
Authors: Tran Hiep T , Gordenin Dmitry A , Resnick Michael A 
Published: January 2021

Abstract
We have investigated the effects of mismatch repair on 1- to 61-bp deletions in the yeast Saccharomyces cerevisiae. The deletions are likely to involve unpaired loop intermediates resulting from DNA polymerase slippage. The mutator effects of mutations in the DNA polymerase δ (POL3) gene and the recombinational repair RAD52 gene were studied in combination with mismatch repair defects. The pol3-t mutation increased up to 1000-fold the rate of extended (7-61 bp) but not of 1-bp deletions. In a rad52 null mutant only the 1-bp deletions were increased (12-fold). The mismatch repair mutations pmsl, msh2 and msh3 did not affect 31- and 61-bp deletions in the pol3-t but increased the rates of 7- and 1-bp deletions. We propose that loops less than or equal to seven bases generated during replication are subject to mismatch repair by the PMSI, MSH2, MSH3 system and that it cannot act on loops ≤31 bases. In contrast to the pol3-t, the enhancement of 1-bp deletions in a rad52 mutant is not altered by a pmsl mutation. Thus, mismatch repair appears to be specific to errors of DNA synthesis generated during semiconservative replication.
Response of Two Heat Shock Genes to Selection for Knockdown Heat Resistance in Drosophila melanogaster
Authors: McColl Gawain , Hoffmann Ary A , McKechnie Stephen W 
Published: January 2021

Abstract
To identify genes involved in stress resistance and heat hardening, replicate lines of Drosophila melanogaster were selected for increased resistance to knockdown by a 39° heat stress. Two selective regimes were used, one with and one without prior hardening. Mean knockdown times were increased from ~5 min to &gt;20 min after 18 generations. Initial realized heritabilities were as high as 10% for lines selected without hardening, and crosses between lines indicated simple additive gene effects for the selected phenotypes. To survey allelic variation and correlated selection responses in two candidate stress genes, hsr-omega and hsp68, we applied denaturing gradient gel electrophoresis to amplified DNA sequences from small regions of these genes. After eight generations of selection, allele frequencies at both loci showed correlated responses for selection following hardening, but not without hardening. The hardening process itself was associated with a hsp68 frequency change in the opposite direction to that associated with selection that followed hardening. These stress loci are closely linked on chromosome III, and the hardening selection established a disequilibrium, suggesting an epistatic effect on resistance. The data indicate that molecular variation in both hsr-omega and hsp68 contribute to natural heritable variation for hardened heat resistance.
The stoned Locus of Drosophila melanogaster Produces a Dicistronic Transcript and Encodes Two Distinct Polypeptides
Authors: Andrew Justen , Smith Michiko , Merakovsky John , Coulson Michelle , Hannan Frances , Kelly Leonard E 
Published: January 2021

Abstract
The stoned gene of Drosophila metanoguster is required for normal neuronal function in both adult and larva. We have identified DNA sequences that lie within a genetic region that is known to include the stoned gene and that also reveal restriction site variations in two stoned lethal mutants. This genomic region contains a single transcription unit coding for an ~8.4-kb transcript. The transcript is preferentially expressed in the head of adult flies. The isolation and sequencing of cDNA and genomic clones reveals that stoned appears to encode a dicistronic mRNA, although the possible existence of other forms of mRNA cannot be excluded. Antibody cross-reactivity shows that two proteins are translated from the stoned locus in vivo. Both open reading frames (ORFs) encode novel proteins. The protein encoded by the first ORF contains four tandemly repeated motifs, and one domain of the protein encoded by the second OW shows similarity to a family of proteins (AP50s) associated with clathrin assembly protein complexes.
Epistatic Control of Non-Mendelian Inheritance in Mouse Interspecific Crosses
Authors: Montagutelli Xavier , Turner Rowena , Nadeau Joseph H 
Published: January 2021

Abstract
Strong deviation of allele frequencies from Mendelian inheritance favoring Mus spretus-derived alleles has been described previously for X-linked loci in four mouse interspecific crosses. We reanalyzed data for three of these crosses focusing on the location of the gene(s) controlling deviation on the X chromosome and the genetic basis for incomplete deviation. At least two loci control deviation on the X chromosome, one near Xist (the candidate gene controlling X inactivation) and the other more centromerically located. In all three crosses, strong epistasis was found between loci near Xist and marker loci on the central portion of chromosome 2. The mechanism for this deviation from Mendelian expectations is not yet known but it is probably based on lethality of embryos carrying particular combinations of alleles rather than true segregation distortion during oogenesis in F1 hybrid females.