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At least 19 recordsLinked to original sources
PubMed1978

Biochemical genetics of the alpha-keto acid dehydrogenase complexes of Escherichia coli K12: genetic characterization and regulatory properties of deletion mutants.

Twenty-eight spontaneous auxotrophic aroP mutants with deletions in the azi--nadC--aroP--aceE--aceF--lpd region of the Escherichia coli K12 chromosome were characterized genetically with respect to various azi, nadC, ace and lpd markers by P1-mediated transduction. One mutant (Kdelta18; aroP--lpddelta) had a deletion which extended through the aceE and aceF genes to end within the lpd gene. The polarity of the ace operon (aceE to aceF) was confirmed. It was concluded that 10 out of 15 deletions generating a strict requirement for acetate terminated in the aceE gene. Of the ten, three mutants (Kdelta22, Cdelta41 and Cdelta41) synthesized detectable dihydrolipoamide acetyltransferase (the aceF gene product) and seven were assumed to possess deletions generating polar effects on aceF gene expression. Five deletions appeared to extend into the aceF gene. A further five deletions, which limited the expression of the ace operon without generating an Ace- phenotype or a complete Ace- phenotype, ended closest to the aroP-proximal aceE markers. The opposite ends of all these deletions appeared to terminate before (10), within (2) or extend beyond (9) the nadC gene. There was no obvious correlation between the deletion end-points and the corresponding lipoamide dehydrogenase activities, which ranged from 30 to 95% of parental levels in different deletion strains. The remaining seven deletions simply extended between the aroP and nadC genes (nad--aroPdelta) without affecting expression of the ace operon. Regulation of the synthesis of the pyruvate and alpha-ketoglutarate dehydrogenase complexes was investigated in some of the parental and deletion strains under different physiological conditions including thiamin-deprivation. The results indicate that the syntheses of the two dehydrogenase complexes are independently regulated. Expression of the lpd gene appears to be coupled to complex synthesis but can be dissociated under some conditions. Mechanisms for regulating lpd gene expression are discussed and an autogenous mechanism involving uncomplexed lipoamide dehydrogenase functioning as a negatively acting repressor at the operator site of an independent lpd gene is proposed as the simplest mechanism which is consistent with all available information.

Chromosome Deletion↗
PubMed1992

Molecular and genetic characterization of cytochrome oxidase-negative Aeromonas salmonicida isolated from coho salmon (Oncorhynchus kisutch).

Cytochrome oxidase variants of the bacterial fish pathogen, Aeromonas salmonicida, were characterized for genetic and molecular homology with cytochrome oxidase-positive isolates that typically induce furunculosis in salmonids. Protein and lipopolysaccharide moieties of the cytochrome oxidase-negative variants were similar to their typical counterparts, based on sodium-dodecyl-sulfate polyacrylamide gel electrophoresis. Pathogenicity of aberrant isolates to brook trout (Salvelinus fontinalis) was similar to typical cytochrome oxidase-positive isolates. Colorimetric deoxyribonucleic acid (DNA) hybridization in 96-well microplates yielded homology values greater than 82.5% for typical aberrant A. salmonicida isolates when photobiotinylated DNA for reference A. salmonicida 3.101 was used as a probe. The only variation of these isolates from typical A. salmonicida was a negative cytochrome oxidase reaction.

Aeromonas↗
PubMed1979

Respiration-deficient Chinese hamster cell mutants: genetic characterization.

We present here genetic experiments with a series of Chinese hamster cell mutants defective in oxidative energy metabolism. The mutations were all shown to be recessive in intraspecies hybrids. Thirty-five mutants were sorted into eight complementation groups, but one of these mutants failed to complement representatives of two distinct complementation groups. The possibility was raised that this is a cell carrying two mutations or a deletion. Because of the greatly different frequencies with which such mutants could be isolated from two different Chinese hamster cell lines, CCL16 (DON) and V79, the stability of representatives from each cell line was examined, and it was found that revertants could be obtained after treatment with mutagens, while spontaneous revertants appeared at unmeasurable or extremely low frequencies, with one exception. The mutant with a very noticeable frequency of spontaneous reversion was defective in mitochondrial protein synthesis, and the question arose whether the mutation was on the mitochondrial genome. A detailed fluctuation analysis of reversion rate and comparison with rates for other mutations was consistent with a nuclear mutation. This conclusion was supported by experiments involving fusions with cytoplasts.

Animals↗
PubMed1992

Genetic characterization of Legionella pneumophila serogroup 1 associated with respiratory disease in Australia.

Techniques were developed for genetic characterization of Legionella pneumophila serogroup 1 by using restriction fragment length polymorphism analysis. Allozyme analysis provided an index of the discrimination achieved by restriction fragment length polymorphism. Isolates from human cases of legionellosis were examined by both methods, and their profiles were compared with reference strains of L. pneumophila serogroup 1 obtained from the American Type Culture Collection. Eighteen distinct clones were evident among the isolates examined. Both methods could be used to trace the source of an outbreak of legionellosis caused by L. pneumophila serogroup 1.

Australia↗
PubMed2025

Comprehensive clinical and genetic characterization of hyperprogressive biliary tract cancer during PD-1 blockade monotherapy: case report and literature review.

BACKGROUND: Some genetically characterized patients show the rapid disease progression during immune checkpoint inhibitors (ICIs) monotherapy, a phenomenon known as hyperprogressive disease (HPD). CASE PRESENTATION: Herein we report a relevant case of biliary tract cancer (BTC) that initially responded to gemcitabine plus oxaliplatin (GEMOX) and PD-1 blockade but subsequently developed HPD in the process of PD-1 blockade maintenance therapy, leading to death within two weeks. Genomic analysis revealed mutations in CDKN2A, PIK3CA, KRAS and EPHA2 in both baseline and hyperprogressive plasma and tumor samples. Notably, higher KRAS mutation abundance was observed in plasma and ascites after disease progression. CONCLUSIONS: These findings suggest a potential association between these negative genes especially KRAS mutation and HPD. Therefore, administration of PD-1 blockade monotherapy in this subgroup of patients harboring KRAS mutation should be performed with caution. Further studies are warranted to confirm these results and explore the correlation between genomic mutations and HPD.

Humans↗
PubMedDate not supplied

Molecular and genetic characterization and physical mapping of 11 new markers detecting multiallele restriction fragment length polymorphisms on the short arm of human chromosome 3.

Genetic markers with high degrees of polymorphisms are of vital importance in the construction of high resolution (2-4 cM) linkage maps of human chromosomes as specified in the short-term goals of the Human Genome Initiative. In this paper, we report on molecular and genetic characterization and physical localization of 11 new multiallele restriction fragment length polymorphism markers on human chromosome 3p. Ten of these represent three- and four-allele polymorphisms of the base substitution type probably at two adjacent restriction sites. One has been identified as a novel mini-satellite sequence comprising a variable copy number tandem repeat array of a G/T-rich 79-bp sequence. This collection of multiallele polymorphic (PIC values: 0.40-0.60) markers should prove valuable and increase the resolution power of the available chromosome 3p genetic markers.

Alleles↗
PubMed1992

Genetic characterization of an antigenic subtype of eastern equine encephalomyelitis virus.

A 1983 human Mississippi isolate of eastern equine encephalomyelitis virus (EEEV), recently identified as an antigenic subtype of the North American variety, was genetically characterized using oligonucleotide fingerprinting and sequencing of viral RNA. This strain was found to be very closely related to other North American EEEV isolates from the same time period. Phylogenetic analysis suggested that this subtype belongs to a single EEEV lineage in North America. Two amino acid substitutions in the E2 envelope glycoprotein, not seen in either other isolates sequenced, probably contributed to the antigenic difference with respect to other EEEV strains. These substitutions include threonine for lysine at position 71, resulting in the addition of a potential N-linked glycosylation site, and lysine for glutamic acid at position 147.

Amino Acid Sequence↗
PubMed1992

Cloning and genetic characterization of a Helicobacter pylori flagellin gene.

Helicobacter pylori produces polar sheathed flagella, which are believed to be essential for the bacterial colonization of the human gastric mucosa. Here we report on the cloning and genetic characterization of a H. pylori gene encoding the subunit of the flagellar filament, the flagellin. Screening of a genomic library of H. pylori with an oligonucleotide probe derived from the N-terminal amino acid sequence of purified flagellin resulted in a recombinant plasmid clone carrying the flagellin-encoding gene flaA on a 9.3 kb Bg/II fragment. The nucleotide sequence of flaA revealed an open reading frame of 1530 nucleotides, encoding a protein with a predicted molecular mass of 53.2 kDa, which is similar in size with the purified flagellin protein in SDS-polyacrylamide gel electrophoresis. Sequence alignment of H. pylori flagellin (FlaA) with other bacterial flagellins demonstrates a high degree of similarity in the amino-terminal and carboxy-terminal regions, including those of the closely related genus Campylobacter (56% overall identity with Campylobacter coli flaA), but little homology in the central domain. Southern hybridizations of chromosomal DNA with flaA-specific probes did not reveal the presence of additional homologous flagellin genes in H. pylori. Sequence analysis of the flaA flanking regions and mapping of the flaA mRNA start site by a primer extension experiment indicated that transcription of the gene is under the control of a sigma 28-specific promoter sequence in H. pylori. The region upstream of the flaA promoter is subject to local DNA modification, resulting in the masking of two out of three closely linked HindIII restriction sites in the chromosome of strain 898-1. Escherichia coli strains harbouring the recombinant plasmid did not produce full-length flagellin and data obtained with FlaA fusion proteins using an E. coli plasmid expression system suggest that a distinct nucleotide sequence in the gene interferes with productive translation of this protein in E. coli.

Amino Acid Sequence↗
PubMed1977

The isolation and genetic characterization of extrachromosomal chloramphenicol and oligomycin-resistant mutants from the petite-negative yeast Kluyveromyces lactis.

Spontaneous mutants of the petite-negative yeast Kluyveromyces lactis, resistant to the antibiotics chloramphenicol and oligomycin, were isolated and genetically characterized. Three chloramphenicol-resistant mutants showed non-Mendelian inheritance when crossed to sensitive parents. Of 5 oligomycin-resistant strains studied, three exhibited resistance due to the presence of an extrachromosomal mutation. The resistance of the other two deriving from a nuclear and recessive mutation. When two factor crosses in trans configuration were performed between two of the chloramphenicol and the five oligomycin-resistant mutants a polarity in recombination was observed with a predominance of sensitive (OSCS) over resistant (ORCR) reciprocal recombinants. Allelism tests carried out among the oligomycin-resistant mutants indicated the presence of at least two distinct extrachromosomal regions responsible for the resistance.

Chloramphenicol↗
PubMed1975

Restriction endonuclease analysis of mitochondrial DNA from grande and genetically characterized cytoplasmic petite clones of Saccharomyces cerevisiae.

Digestion of grande mitochondrial DNA (mtDNA) BY EcoRI restriction endonuclease gives rise to nine fragments with a total molecular weight of 51.8 x 10(6). HindIII digestion yields six fragments with a similar total molecular weight. Specific restriction fragments can be detected despite the fact that yeast mtDNA consists of a heterogeneous distribution of randomly broken molecules. Digestion patterns of 10 genetically characterized petite clones containing various combinations of five antiobiotic resistance markers indicate that the petite mtDNA predominantly represents deletion of the grande genome. The petite mtDNAs contained up to seven EcoRI restriction fragments which comigrate with grande restriction fragments, and at least one fragment that did not correspond to any in the grande. Some strains contained multiple fragments with mobility different from that of grande; these fragments were usually present in less than molar concentrations. The genetic markers were associated with individual sets of restriction fragments. However, several internal inconsistencies prevent the construction of a definitive genetic fragment map. These anomalies, together with the digestion patterns, provide strong evidence that, in addition to single contiguous deletion, other changes such as multiple deletion and heterogeneity of mtDNA populations are present in some of the petite mtDNAs.

DNA Restriction Enzymes↗
PubMed2026

Morphological characterization, genetic diversity and population structure of the rice blast pathogen Magnaporthe oryzae in Northeast India.

The blast pathogen, Magnaporthe oryzae, is one of the most destructive fungal pathogens of rice worldwide, yet its morphological features, genetic diversity and population structure in Northeast India remain poorly understood. In this study, twenty‒two M. oryzae isolates collected from eight states of Northeast India were characterized using morphological, molecular, and population genetic analyses. Morphological characterization revealed whitish to greyish‒white mycelia with sparse sporulation and colony diameters ranged from 36 to 90 mm, classifying the isolates into 14 fast and 8 slow‒growing groups. Whole genome sequencing was performed to enable both ITS‒based identification and SSR locus mining from the assembled genomes. Molecular identification using ITS rDNA sequences confirmed all isolates as M. oryzae, with 95.5-100% similarity. Phylogenetic analysis grouped the isolates into two major clades and identified seven ITS sequence types (GenBank Accessions: PX273287-PX273293). Genetic diversity assessed using 30 SSR markers revealed substantial polymorphism, with 1-7 alleles per locus and polymorphism information content (PIC) values ranging from 0.00 to 0.81. Heatmap clustering, dendrogram analysis, and distance metrics consistently identified two major genetic groups, with some isolates forming nearly identical clusters and others showing moderate divergence. Principal Component Analysis (PCA) and Principal Coordinates Analysis (PCoA) accounted for 87.8% of the total variance (PC1 and PC2 accounted for 54.4% and 33.4% respectively of the total variance) and revealed distinct outliers. Analysis of Molecular Variance (AMOVA) attributed 80% of the total genetic variation to differences among populations while only 20% was attributed to within population differences highlighting significant inter‒population divergence and clonal population structure. The study revealed substantial morphological and genetic diversity among M. oryzae populations in Northeast India, underscoring the need for region‒specific disease management strategies.

India↗
PubMed1992

Biochemical and genetic characterization of the multidrug resistance phenotype in murine macrophage-like J774.2 cells.

The development of multidrug resistance (MDR) in malignant tumors is a major obstacle to the treatment of many cancers. MDR sublines have been derived from the J774.2 mouse macrophage-like cell line and utilized to characterize the phenotype at the biochemical and genetic level. Two isoforms of the drug resistance-associated P-glycoprotein are present and distinguishable both electrophoretically and pharmacologically. Genetic analysis has revealed the presence of a three-member gene family; expression of two of these genes, mdr1a and mdr1b, is associated with MDR whereas the expression of the third, mdr2, is not. Studies of these three genes have revealed similarities and differences in the manner in which they are regulated at the transcriptional level, and have suggested that post-transcriptional effects may also be important.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1975

Genetic characterization of adenine-3 mutants induced by 4-nitroquinoline 1-oxide and 4-hydroxyaminoquinoline 1-oxide in Neurospora crassa.

Specific locus mutations induced by the chemical carcinogens, 4-nitroquinoline 1-oxide (4NQO) and 4-hydroxyaminoquinoline 1-oxide (4HAQO), have been characterized to obtain a presumptive identification of the genetic alterations at the molecular level. One hundred eighty-four 4NQO-induced and 219 4HAQO-induced ad-3 mutants of Neurospora crassa obtained in previous studies were studied with a series of genetic tests that permits determination of their genotype and the frequencies of point mutations and multilocus deletions. These tests have shown that the spectrum of ad-3 mutations among 4NQO-induced mutants is similar to that of 4HAQO-induced mutants. None of the 4NQO- or 4HAQO-induced mutants is a multilocus deletion mutant. The ratio of ad-3A to ad-3B mutants is the same in the two samples, as well as the frequencies of complementing ad-3B mutants. These data suggest, then, that the mechanism of mutation induction by 4NQO in N. crassa is identical to that of 4HAQO. It is not clear, however, whether 4NQO is mutagenic per se or reduction of 4NQO to 4HAQO is the first step involved in the mutagenesis of this compound in Neurospora. The heterotaryon tests have shown that the relatively high frequencies of 4NQO- or 4HAQO-induced ad-3B mutants show allelic complementation and that most of the complementing ad-3B mutants (74% of 4NQO induced and 71% of 4HAQO induced) have nonpolarized complementation patterns. From this we conclude that both agents induce predominantly base-pair substitution mutations in N. crassa. The results are in agreement with our other studies which show that potent chemical carcinogens induce predominantly base-pair substitution mutations in N. crassa.

Adenine↗
PubMed1992

Antigenic and genetic characterization of the haemagglutinins of recent cocirculating strains of influenza B virus.

The antigenic and genetic characteristics of the haemagglutinins of influenza type B viruses isolated since 1988 during periods of both widespread activity (1990/1991) and sporadic activity (1989/1990) were examined using microneutralization tests and direct RNA sequencing. During 1989/1990, influenza B viruses representative of two distinct lineages antigenically and genetically related to either B/Victoria/2/87 or B/Yamagata/16/88 were isolated, and a minor drift variant of B/Yamagata/16/88, B/Hong Kong/22/89, was identified. In 1990/1991, B/Hong Kong/22/89- or B/Yamagata/16/88-like viruses accounted for the majority of the influenza virus isolates in most countries. Sequence analysis of the HA1 domains of representative viruses confirmed the continued existence of two main lineages among recent strains of influenza B virus and identified unique amino acid changes that could account for the altered antigenic reactivity of some variants. Sequence analysis of the HA2 domains of some of the recent influenza B viruses allowed for a comparison of the evolutionary rates and patterns between the HA1 and HA2 domains.

Amino Acid Sequence↗
PubMedDate not supplied

Genetic characterization of the mechanism by which certain strains of Escherichia coli survive in high kanamycin concentrations.

By genetic studies, it was tried to find the mechanism by which a bacterial fraction from different isolated clinical cultures resistant to 25 micrograms/ml of kanamycin can grow in media containing 500 micrograms/ml of kanamycin (at a frequency of about 10(-5)). This study was done in six clinical isolates of Escherichia coli resistant to more than three antibiotics. The results from the bacterial fraction (subpopulation) resistant to high concentrations of kanamycin in the level of resistance to aminoglycoside and non-aminoglycoside antibiotics, in the conjugation experiments, and in the percentage of resistant bacteria to 500 micrograms/ml of kanamycin when the subpopulations were subsequently cultivated in the absence of antibiotics suggest that genetic amplification occurred when one of the strains was growing in the presence of 500 micrograms/ml of kanamycin. Moreover, this strain increased its frequency of survival in high kanamycin concentrations when it was transduced by bacteriophage P1, propagated in cultures resistant to 500 micrograms/ml of kanamycin.

Conjugation, Genetic↗
PubMed1977

Physical and genetic characterization of deletion mutants of simian virus 40 constructed in vitro.

Mutants of simian virus 40 (SV40), with deletions ranging in size from fewer than 3 to 750 base pairs located throughout the SV40 genome, were obtained by infecting CV-1P cells with linear SV40 DNA and DNA of an appropriate helper virus. The linear DNA was obtained by complete cleavage of closed circular DNA with Hae II or Bam HI endonuclease or partial cleavage with either Hae III endonuclease or nuclease S1, followed, in some cases, by mild digestion with phage lambda 5' -exonuclease. The following mutants with deletions in the late region of the SV40 genome were obtained and characterized. Ten, containing deletions at the Hae II endonuclease site (map location 0.83), define a new genetic complementation group, E, grow extremely slowly without helper virus, and cause alterations only in VP2. Two mutants with deletions in the region 0.92 to 0.945 affect both VP2 and VP3, demonstrating that VP3 shares sequences with the C-terminal portion of VP2. The mutant with a deletion at 0.93 is the first deletion mutant in the D complementation group and is also temperature sensitive; the mutant with a deletion at 0.94 is viable and grows normally. Three mutants with deletions at the EcoRI endonuclease site (0/1.0) and eleven with deletions at the BamHI endonuclease site (0.15) fall into the B/C complementation group. Six additional mutants with deletions at the BamHI endonuclease site are viable, growing more slowly than wild type. VP1 is the only polypeptide affected by mutants in the B/C group. A mutant with a deletion of the region 0.72 to 0.80 has a polar effect, failing to express the E, D, and B/C genes. Mutants with deletions in the early region (0.67 counterclockwise to 0.17) at 0.66 to 0.59, 0.48, 0.47, 0.33, and 0.285 to 0.205 are all members of the A complementation group. Thus, the A gene is the only viral gene in the early region whose expression is necessary for productive infection of permissive cells. Since mutants with deletions in the region 0.59 to 0.54 are viable, two separate regions are essential for expression of the gene A function: 0.66 to 0.59 and 0.54 to 0.21. Mutants with deletions at 0.21 and 0.18 are viable. Approximate map locations of SV40 genes and possible models for their regulation are discussed.

Cell Line↗
PubMed2024

Genetic characterization and selection of litter size traits of Guizhou Black goat and Meigu goat.

The aim of this study is to explore the genetic characteristics of Guizhou Black goats and Meigu goats and their relationship to reproductive performance through population structure analysis, genetic diversity assessment, and selection signal analysis. Blood samples of 19 Guizhou Black goats and 11 Meigu goats were collected for whole-genome high-throughput sequencing. Using PCA and ADMIXTURE analyses, their population structure and genetic relationships were revealed. Further genetic diversity analysis showed that although there is significant population differentiation, the levels of genetic diversity are similar. Subsequently, these goats were categorized into high-yield and low-yield groups based on their litter sizes, with 15 goats in each group. Then, a selection signal analysis was performed using FST and π ratios for 33,563 SNP loci. The results identified six candidate genes, including KCNIP4, GFRA2, and DGKH, which are significantly associated with high litter performance. These findings enhanced our understanding of the genetic characteristics and population structure of Guizhou Black goats and Meigu goats. Moreover, they provide an important theoretical foundation and scientific basis for further breeding improvements.

Animals↗