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Results for “Genetic Complementation Test”

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At least 55 records · Page 3Linked to original sources
PubMed1975

Properties of cytoplasmic mutants of Saccharomyces cerevisiae with specific lesions in cytochrome oxidase.

Two mutants with specific defects in cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) have been isolated from cultures of Saccharomyces cerevisiae exposed to the mutagens ethyl-methane sulfonate and Mn++. The mutations have been shown to be extranuclear by two criteria. The phenotype persists in diploids formed by a cross with a p-o strain of yeast of the opposite mating type. Tetrad analysis indicates a non-Mendelian segregation (4:0 and 0:4) of the mutations. Both mutants show a total absence of cytochrome oxidase activity and of spectral cytochromes a and as. One of the mutants has been shown to be missing a polypeptide synthesized by mitochondria. The migration of this protein on polyacrylamide gels corresponds to the highest-molecular-weight subunit of cytochrome oxidase.

Diploidy↗
PubMed1976

Functional genetic expression of eukaryotic DNA in Escherichia coli.

We have isolated a segment of DNA from the eukaryote Saccharomyces cerevisiae (baker's yeast) as a viable molecular hybrid of bacteriophage lambda DNA which, when integrated into the chromosome of an E. coli histidine auxotroph, allows this bacterium to grow in the absence of histidine. The nonrevertable, histidine auxotroph lacks the enzymatic activity of imidazole glycerol phosphate (IGP) dehydratase (EC 4.2.1.19). From genetic experiments, we conclude that expression of the segment of yeast DNA results in the production of a diffusible substance and that transcription necessary for the complementation is most likely initiated from the segment of eukaryotic DNA.

Acetoxyacetylaminofluorene↗
PubMed1977

On the location of palindromes in immunoglobulin genes.

We present a statistical method for detection of palindromes in mRNA or DNA, starting from the protein sequence. Analysis of immunoglobulin genes by this method demonstrates that palindromic sequences are not randomly distributed. They are located at each side of the hypervariable regions in the variable (V) genes, whereas no such regular design is observed in the constant (C) genes. In addition, palindromic sequences overlap the V-C junction in all immunoglobulin classes and significant palindromes are present near residue 216 of the heavy chain, which is the end of deletions in many heavy chain diseases. The relevance of these palindromes to gene translocation and generation of diversity in antibodies is discussed.

Base Sequence↗
PubMed1979

A new glnA-linked regulatory gene for glutamine synthetase in Escherichia coli.

Mutations in the glnA region of the Escherichia coli chromosome due to Mu prophage insertion result in two phenotypic classes. One class is Gln- and does not synthesize glutamine synthetase[L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] under any growth condition. The other class produces a low level of glutamine synthetase under all growth conditions and is uncoupled from the regulatory effects of mutations in the glnF and glnD genes. Complementation analysis demonstrates that these two classes of insertions are in different cistrons. From these data we suggest that a regulatory gene, glnG, tightly linked to glnA, mediates both activation and repression of glutamine synthetase synthesis. An analysis of the evidence accumulated to date makes it unlikely that glnG is the only gene in the glnA region involved in the complex system of nitrogen regulation.

Bacteriophage mu↗
PubMed1979

Nitrogen control in Salmonella: regulation by the glnR and glnF gene products.

The product of the glnR gene is required for nitrogen regulation of the synthesis of glutamine synthesis (Gln synthetase) [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] and two periplasmic transport proteins that are subject to nitrogen control in Salmonella. Strains with mutations to loss of function of the glnR product [e.g., a strain with a Tn10 insertion or one with an ICR-induced (frameshift) mutation in glnR] have about 3% as much Gln synthetase as a fully derepressed wild-type strain and are unable to increase synthesis of this enzyme or periplasmic transport proteins in response to nitrogen limitation. The structural gene for Gln synthetase, glnA, and those for the periplasmic transport proteins are unlinked on the chromosome; thus, glnR appears to encode a diffusible positive regulatory element. Consistent with this, the mutant glnR allele is recessive to the wild-type allele with regard to expression of glnA (synthesis of Gln synthetase). Although glnR is closely linked to glnA, strains with mutations to complete loss of function of the glnR product can be distinguished from glnA strains by their ability to produce detectable Gln synthetase and to grow in the absence of glutamine. To demonstrate unequivocally that glnR is distinct from glnA, we have purified and characterized Gln synthetase from a strain with a Tn10 insertion in glnR. Because the properties of Gln synthetase from the insertion mutant, most importantly the carboxyl-terminal sequence of amino acids, are the same as those of synthetase from wild type, the Tn10 insertion cannot be in glnA (if it were, the carboxyl terminus of Gln synthetase would have to be altered); therefore we conclude that the Tn10 insertion is in a regulatory gene, glnR, which is distinct from glnA. A model for the function of the glnR product together with the previously defined glnF product in mediating nitrogen control is discussed.

Carrier Proteins↗
PubMed1975

Differential sensitivities and the target of heat-induced recombination at the base of the X chromosome of Drosophila melanogaster.

The effect of heat on two small adjacent segments at the base of the X chromosome was examined. Recombination in the two segments delimited by recessive lethals was measured after treatment with 30 degree and 34 degree. Both segments were sensitive at 30 degree, while only the proximal one responded to 34 degree treatment. When the same segments were studied in structural heterozygotes (for deletions) the relative increase in recombination was greater, suggesting that heat exerts its effect on the "pairing" rather than the "exchange" components of crossing over. The effect of c (3) G/+ on the same segments in both homozygous and heterozygous structurals was studied. The results indicate that this meiotic mutant mediates its effect on a step different than that affected by heat.

Animals↗
PubMed1975

Negative complementation at the notch locus of Drosophila melanogaster.

Four Abruptex alleles (AxE1, AxE2, Ax9B2, and Ax16172) have been mapped within the Notch locus. Based on their visible phenotypes and their interactions with one another and with N mutations, the Ax alleles can be divided into two groups. Heterozygous combinations of members of the same group are intermediate in phenotype compared to the respective homozygotes, whereas heterozygotes of Ax alleles from different groups exhibit negative heterosis, being much less viable and more extremely mutant than either homozygote. It is suggested that the Notch locus is a multi-functional regulator ("integrator") gene, whose product possesses both "repressor" and "activator" functions for the processes it regulates.

Animals↗
PubMed1976

Substrate-specific enzyme variation in natural populations of Drosophila pseudoobscura.

By using a number of different alcohols as substrates, eight alcohol dehydrogenase loci were discovered in Drosophila pseudoobscura. Each of these loci can take more than one substrate. Several of these loci differed in their tissue specificities and activity patterns during development. The genic variation in natural populations was studied at four of these loci and three of them were polymorphic. A quantitative study of substrate-specific differences among alleles of the same locus produced negative results. This result appears to be typical of most studies done on this aspect. From this it was concluded that the substrate specificity of enzymes is not an important factor in determining the greater amount of genic variation at Group II loci than at Group I loci, as proposed by KOJIMA, GILLESPIE and TOBARI (1970). There are several observations which suggest a different explanation for the differences in the genic variability at Group I and Group II loci: (1) There are, on an average, more isozyme loci (loci with similar substrate specificity) for enzymes in Group II than in Group I; (2) The null alleles are far more common at Group II loci than at Group I loci; (3) There is significant heterogeneity in the number of alleles and the heterozygosities at loci within each of these two groups of enzymes; (4) Relatively higher levels of genic variation are observed at Group II loci even in populations which appear to be living in homogeneous environments; and (5) Some loci (e.g. esterases) are highly polymorphic in most species investigated by gel electrophoresis techniques. Based on these general observations, it is proposed that (1) the substrate-specific differences are between isozyme loci and not between alleles of a given locus, and (2) neutral alleles are proportionately far more common at loci at Group II than at loci in Group I, because the former is under less selection constraint than the latter.

Alcohol Oxidoreductases↗