Search

Mild acid hydrolysis of the glycolipid derived @om a Salmonella Rd2 mutant led to the liberation of three major split products which, after separation by electrophoresis, were identified as free 2-keto-3-deoxyoctonate (KDO), KDO-7-phosphorylethanolamine, and L-glycero-α-D-mannoheptosyl-l,5-KDO. [ABSTRACT FROM AUTHOR]

A method is described permitting the detection and approximate determination of adenine and guanine in various materials by the aid of specifically reacting fungal mutations, the purines in question first having been separated by filter-paper chromatography. [ABSTRACT FROM AUTHOR]

The article presents a biography of biologists Hermann J. Muller. Born on December 12, 1890, Muller devoted his life in articulating the dangers of radiation and overpopulation. He demonstrated the genetic mutation in a fruit fly exposed with X-ray at the Fifth International Congress of Genetics in Berlin, Germany in 1927. The author deals with the three confrontations between the scientific integrity of Hermann Muller and the obsolete attitudes of human societies.

The Cbl-1 mutant of Bacillus subtilis 168 WT is the result of a spontaneous mutation presenting a pleiotropic character. In this paper, the results of the morphological and chemical analyses of the cell walls isolated from both strains are compared. When either the whole cells or the isolated cell walls of both strains were fixed with osmium tetroxide, the examination by electron microscopy showed extensive morphological differences in structure due to the partial destruction of the mutant cell walls. The chemical investigations performed on the isolated cell walls revealed surprising differences in chemical structure. In the cell walls of the mutant, teichoic acid was completely missing and was replaced by protein. A major protein-containing fraction accounting for about 50% of the material solubilized by autolysis of the mutant cell walls was isolated. Polyacrylamide gel electrophoresis showed that this fraction was composed mainly of a single protein of high molecular weight When denatured by sodium dodecyl sulfate treatment in the presence of β-mercaptoethanol, the protein yielded by gel electrophoresis two major bands with molecular weights of approximately 105000 and 155000, respectively. The molecular weight of the Cbl-1 cell wall protein determined by high speed sedimentation equilibrium was 255 600. [ABSTRACT FROM AUTHOR]

This article presents a case report of two sisters, similarly affected with atrichia, papular lesions and also with mental retardation. The patients were born with hair on the scalp, which was shed normally and was not replaced. Histologically, the papules resulted from cystic malformation of hair follicles. On the basis of medical examination and analysis, it is concluded that these cases represent a severe manifestation of the autosomal recessive gene mutation which causes atrichia with papular lesions.

The presence of vitamin A in the medium results in a large increase in Β-carotene content in wild-type Phycomyces blakesleeanus; in carB mutants. which accumulate phytoene. and carR mutants. which accumulate lycopene, the presence of vitamin A results in an increase in these intermediates. In carA mutants. which usually form no carotenoids. vitamin A partially counteracts the mutational block and allows Β-carotene synthesis. Vitamin A is not itself converted to Β-carotene. Β-ionone. long known as a stimulator of carotenogenesis, can also counteract carA mutations. The effects of vitamin A and Β-ionone do not occur in the presence of the protein-synthesis inhibitor cycloheximide. Vitamin A and Β-ionone stimulate carotenogenesis through the normal pathway. probably by interaction with the carA gene product. [ABSTRACT FROM AUTHOR]

An apparent fresh mutation has been identified at the human transferase locus (Gt) that has resulted in an occurrence of the heterozygous state for galactosemia (Gt[sup 4]Gt[sup 5]). The individual concerned is the mother of a child with galactosemia, neither of whose parents was found to be heterozygous for galactosemia. Recently discovered human genetic markers and established blood group antigens have been used to test for non-paternity as an alternative explanation to mutation. Paternity was proven in this instance with greater than 98% confidence. This paper illustrates the feasibility of determining biochemically the mutation rates for specific genetic loci and the improved confidence that can be achieved in paternity testing with more recently described human genetic polymorphisms. [ABSTRACT FROM AUTHOR]

Infiltration of indoleacetaldehyde (IAAId) into living tissues of some lower and higher plants gives rise simultaneously to both indoleacetic acid (IAA) and tryptophol (T-ol). But on a molar basis, there is no correlation between the products indicating a dismutation. Expressed juice of Avena coleoptiles by itself, exhibits only IAA forming activity. Approximately two moles of IAAId are consumed for each mole IAA forming at pH 4.5, but only if necessary corrections are made for losses of substrate and products. Addition of reduced NAD or NADP readily induces tryptophol formation. But even at ph 4.5, adding reduced NADP causes greater tryptophol formation, leading to a marked divergence in the acid-alcohol ratio. Varying the pH in the presence of reduced coenzymes also alters the ratio, with alcohol formation predominating. NAD and NADP have no influence on the formation of IAA from IAAId by the whole cytoplasm of Avena coleoptiles. Whole cytoplasm of Asparagus shoots forms both IAA and tryptophol from IAAId, but in widely varying amounts, devoid of any suggestive stoichiometry between the products. With the acetone powder of Avena coleoptiles including the first leaf, data indicating an apparent dismutation of IAAId are obtainable only at pH 4.5. On altering the pH however, unequal amounts of the two products, namely IAA and tryptophol, are formed and hence a different ratio results. Acetone powders of wheat coleoptiles and Asparagus shoots do not yield data supporting dismutation either at pH 4.5 or 7.2. IAA formation in Avena is aerobic while tryptophol formation is seemingly independent of oxygen supply. The former activity is selectively abolished by 10-3 M dithionite while the latter activity suffers a similar suppression in the presence of 10-3 M manganese sulphate. Varying the IAAId concentration results in unequal amounts of the two products, revealing the dissimilar affinity of the two activities for the common substrate. Saturation to a level of 30 percent with ammonium sulphate throws out most of the acid-forming activity whereas the alcohol-forming system appears mostly in the protein fraction precipitated between 30 and 40 percent saturation. The enzyme system of Avena coleoptiles oxidizing IAAId to IAA can also be easily separated by Sephadex gel filtration and its independent activity demonstrated in the total absence of tryptophol formation. Based on the heterogeneous properties of the two activities, metabolism of IAAId in Avena coleoptiles is believed to he mediated by two independent enzyme systems without the intervention of a mutase or a dismutation mechanism. [ABSTRACT FROM AUTHOR]

Aspartokinase I-homoserine dehydrogenase I from Escherichia coli K 12 was subjected to mild proteolysis. A fragment carrying only the desensitized homoserine dehydrogenase activity was purified. It is a dimer having a subunit molecular weight of 55 000 as opposed to 86 000 for the subunit of the native tetrameric enzyme. On the other hand, a threonine sensitive aspartokinase devoid of homoserine dehydrogenase activity was extracted from the mutant Gif 108. The purified protein is shown to have subunits shorter than those of the wild-type enzyme (molecular weight 47 000). It was shown that the two catalytic activities of aspartokinase I-homoserine dehydrogenase I are sequentially distributed on the single polypeptide chain: the aspartokinase activity is located in the amino-terminal section and the homoserine dehydrogenase in the carboxyl-terminal section. The results are discussed in relation to the configuration of the native enzyme and with the possible origin of the bifunctional protein. [ABSTRACT FROM AUTHOR]

It is known that Escherichia coli can incorporate labeled thymidme into its DNA, but it has not been previously possible to measure the incorporation of the other deoxyribonucleosides deoxycytidine, deoxyadenosine, and deoxyguanosine because of degradation of these compounds. The present experiments utilize a mutant of E. coli B lacking deoxyribonucleoside-catabolizing enzymes. This strain, OK441, has mutations affecting the following enzymes: thymidine phosphorylase, purine nucleoside phosphorylase, cytidine deaminase, and adenosine deaminase. The results with OK441 show that E. coli, in contrast to lactobacilli and mammalian cells, does not incorporate any deoxyribonucleoside other than thymidine into its DNA. E. coli may be unable to phosphorylate deoxycytidine, deoxyadenosine, and deoxyguanosine. In agreement. with this suggestion, only thymidine kinase but no other deoxyribonucleotide kinase could be detected in extracts of OK441. [ABSTRACT FROM AUTHOR]

This article studies the origin of apparent gene mutation in drosophila melanogaster. Three groups of experiments were carried out, viz, induction of yellow, white and singed mutations in X chromosomes from a wild type stock, Oregon, recessive lethals induced in X chromosomes from a y w sn, stock and finally yellow, white and singed mutations and hyperploid males in X-chromosornes. The number of mutants tested is too small to give any indication of a possible difference in the viability in connection with visible mutations induced in various stages of spermiogenesis.

The article discusses a research paper on the distribution and ecology of Spartina Townsendii. It describes the general habit and mode of growth of the grass specie. Details are presented with regard to the rapid spread of the grass, including accidental introduction from a foreign country and orgin by mutation from Spartina stricta. It has been found that its chief domain is the mud-flats from one to three feet below highwater mark, where the changes it has brough about are remarkable. Uses of the grass include thatching and mulching.

The article cites the author's reflections concerning mutation and recombination. He mentions that pedagogues take pride in pointing to progress of their pupils, particularly as pertains to penetration of powerful perspectives in the province of their own proficiency. He states that peas were metamorphosed into sweet peas, beans, legumes and monocots and that they were stated to be monoploid, hermaphroditic and with tetrapod nodules on the stems. He mentions that his examinations are revealing natural variation.

The author reflects on the effects of the exposure of human beings to ionizing radiations at low dosage rates. It is stated that an increase in radiation exposure will lead to genetic deaths. It is suggested to have a research program which on three parts including key studies on mutation, studies of animal and human populations.

The light saturation curves for photosynthesis in Lycopersicon esculentum have been studied for a yellow-green mutation and for hormone treated plants. comparisons have been made between saturation point and the size of the photosynthetic unit in these plants. These data suggest a function in the regulation of photosynthetic rates. [ABSTRACT FROM AUTHOR]

The reduction of dichlorophenolindophenol in the presence of 2,3-butanediol can be used as a histochemical indicator for the acetoin reductase catalyzed reaction in viable Bacillus subtilis cells. Using this reaction it was possible to identify mutants blocked in this enzyme. The mutation which causes a lack in acetoin reductase simultaneously causes a loss of diacetyl-methylcarbinol reductase activity and a reduction of diacetyl reductase activity. It was shown that the mutants lack one enzyme protein which carries all three activities. The residual diacetyl reductase activity originated from a different enzyme which could be separated from the protein with the multiple activities. The mutation did not affect acetoin degradation, however it prevented butanediol utilization. [ABSTRACT FROM AUTHOR]

The suppressor-sensitive mutants of phage ø29,susB47 and susN212, do not induce the synthesis of proteins NP1 and H, respectively, when they infect Bacillus subtilis su-. A new polypeptide of molecular weight 75000, smaller than that of protein NP1, is produced in susB47-infected cells. An analysis of the methionine-containing tryptic peptides of protein NP1 and the 75000-molecular- weight polypeptide showed that both proteins are related. When mutants susB47 and susN212 infect B. subtilis su+3, a small amount of proteins NP1 and II, respectively, is synthesized, the level of the suppression being about 10%. The results indicate that the B. subtilis su+3 strain is a suppressor of nonsense mutations. [ABSTRACT FROM AUTHOR]

In the ascomycete fungus, Aspergillus nidulans, mutations in the niaD gene and in five unlinked cnx genes lead to the loss of assimilatory nitrate reductase, and the inability to grow on nitrate as sole nitrogen source. Mutants have been isolated in the niaD gene and in three of the five cnx genes which are temperature-sensitive for growth on nitrate and have nitrate reductase activity when grown at the permissive temperature. The half life of nitrate reductase in the wild-type and in these temperature- sensitive strains has been measured. Temperature-sensitive mutants in the cnxE and cnxF genee havs a nitrate reductase with the same half life as in wild-type strains. Temperature-sensitive mutants in the niaD and cnxH genes have a nitrate reductase with a shorter half life than the wild-type enzyme. These results can be interpreted as indicating that the products of the niaD and cnxH genes are structurally involved in the nitrate reductase molecule, whereas the products of the cnxE and cnxF genes are involved in the formation of a cofactor required for nitrate reductase activity. [ABSTRACT FROM AUTHOR]

An X-ray induced pyridoxamine-deficient mutant in Ophiostoma has been studied, and comparisons are made with two previously described pyridoxamine-less strains as regards its genetical and physiological characteristics. [ABSTRACT FROM AUTHOR]

Nutritional mutations of Ophiostoma multiannulatum representing biochemical types not hitherto isolated were selected for by means of an enrichment technique. The complete medium used contained a carefully-treated liver extract. Among the more notable single-gene mutations obtained, one required the tripeptide glutathione, another one a combination of adenine, histidine, and glycine. Some of the other mutants with complex requirements were probably double mutations. A number of temperature-sensitive mutants were also isolated, none of them being capable of growth above +25° C, or - in two cases - above +27° C. [ABSTRACT FROM AUTHOR]

The genetics of the two major phenotypic classes of oligomycin-resistant yeast mutants have been investigated. All the class II mutants (oligomycin specific) tested show typical cytoplasmic inheritance and the determinants appear located on mtDNA. Evidence is presented that this type of resistance can be conferred by at least two distinct groups of nonallelic cytoplasmic determinants. The class I mutants which show cross resistance to a variety of inhibitors and uncouplers of energy conservation reactions exhibit behaviour on genetic analysis which is not fully understood. Tetrad analysis indicates that a nuclear gene is concerned but many anomalous observations, discussed here, suggestive of the involvement of a cytoplasmic element remain to be explained. [ABSTRACT FROM AUTHOR]

1. Growth of Escherichia coli in the presence of acetoacetate as inducer stimulates the rate of synthesis of two enzymes, an acetoacetyl-CoA: acetate CoA-transferase and a thiolase by a factor of 3000. The combined action of these enzymes allows for the degradation of acetoacetate to acetate and acetyl-CoA. 2. The structural genes for these enzymes, called atoA (CoA-transferase) and atoB (thiolase), and a regulatory gene, atoC, are closely linked, forming an operon (ato operon) with the order his … atoCAB… nalA on the bacterial chromosome. 3. The regulatory gene atoC is defined by a spontaneous mutation to the atoCe state which allows E. coli to grow on butyrate and to synthesize the enzymes of the ato operon, constitutively. This mutation can only be selected for when the enzymes of the C-3 oxidation pathway are themselves formed constitutively. The atoCc state is required for butyrate degradation because this acid does not serve as inducer of the ato operon but requires the CoA-transferase for activation. 4. The evidence so far available indicates that, the atoCc mutation is trans-dominant over the inducible atoC+ state suggesting a positive mechanism of control. 5. The uptake of butyrate is reduced or completely suppressed when mutational lesions prevent the further metabolism of this substrate. [ABSTRACT FROM AUTHOR]

The properties of the catabolic ornithine carbamoyltransferase of Pseudomonas fluorescens are compared to those of the anabolic transferase of the same organism. The comparison is also extended to a mutationally modified enzyme which, in contrast to the catabolic enzyme, is able to synthesize citrulline in vivo. All three activities are measured in the direction of citrulline synthesis. The catabolic ornithine carbamoyltransferase and the mutationally modified enzyme have an approximate molecular weight of 400000 while that of the anabolic enzyme is 100000. The catabolic transferase exhibits a number of regulatory properties which are not observed with the anabolic enzyme: 1. Its saturation by carbamyolphosphate is intensively cooperative. Its half saturation concentration is more than one hundred times higher than the Km of the anabolic enzymes; this explains its inability to perform an anabolic function in vivo. 2. Phosphate, a substrate in the physiological direction of the reaction and a low-energy-level indicator, acts as an activator of the enzyme; it abolishes the cooperativity of the carbamoylphosphate and increases the capacity of the enzymes. 3. ATP, a product of the catabolic pathway and a high-energy4evel signal, reduces the capacity of the enzyme. 4. Putrescine, another product of the catabolic pathway, and its analogs, inhibit the enzyme by decreasing its apparent affinity for carbamoylphosphate. The catabolic transferase of the mutant 1RC204M1 shares all those properties with the wild- type enzyme, but, owing to a reduced cooperativity of carbamoylphosphate, it is able to perform an anabolic function at reduced rate. [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae, the genetic linkage as well as the biochemical characteristics of nine different fatty-acid-synthetase complementation groups have been studied. By spore tetrad analysis, the alleles of these nine groups were established to be located on three genetically unlinked DNA regions on the yeast genome. These regions consist of one separate gene and two clusters comprising two and three adjacent cistrons, respectively. In both clusters the alleles are closely linked within less than one map unit. The cistrons of the first cluster can be assigned to structural genes of the dehydratase and the second reductase, those of the second cluster to the first reductase and two proteins involved in the condensation reaction. Mutants of the separate fascistron produce a fully active fatty acid synthetase complex with all the component enzyme activities unimpaired under the assay conditions employed. The function of the gene product of this cistron is unknown, so far. From the pleiotropic fas-mutants, a fatty-acid-synthetase complex with residual component enzyme activities could not be isolated. It is concluded that, due to the polar transcription of the clustered cistrons in these mutants either none or only an incomplete aggregate is formed with the concomitant inactivation of residual component enzymes. [ABSTRACT FROM AUTHOR]

The incorporation and metabolic alteration of a variety of dietary fatty acids has been studied in wild-type Saccharomyces cerevisiae and a fatty-acid auxotroph which carries a genetic defect iii its fatty-acid synthetase complex. This mutant grows when supplemented with a single even or add domain-length fatty acid ranging from 13-17 carbon atoms. Although incapable of fatty acid synthesis from acetate de novo, the mutant yeast still elongates the dietary fatty acids by one or more C2 units. The extent of elongation is dependent on the chain length of the fatty acid included in the growth medium. It is most evident with tridecanoic acid and insignificant with palmitic acid. All saturated fatty acids are desaturated to an appreciable but varying degree to the corresponding monounsaturated acids. No degradation to lower homologous is observed in the wild-type, nor in the mutant cells. No evidence was obtained to indicate participation of the mutant fatty-acid synthetase complex in the elongation process described. In wild-type yeast, intracellular fatty acid biosynthesis is unimpaired by the addition of free fatty acids to the growth medium and apparently proceeds by a much faster rote than the uptake and elongation of fatty acids from the growth medium. A membrane-bound enzyme analogous to acid :CoA ligase has been isolated from bakers' yeast and its chain-length specificity studied. The optimal chain length with saturated fatty acids is 15 carbon atoms. Unsaturated fatty acids are generally better substrates. The role of fatty acid activation in determining the rate of fatty-acid-dependent yeast mutant growth is discussed. [ABSTRACT FROM AUTHOR]

In the present publication the synthesis of the galactose binding protein and the β-methylgalactoside transport system in Escherichia coli K12 has been shown to be coregulated. With the use of mutants of different regulatory behavior with respect to the galactose operon and the phosphoenolpyruvate-dependent phosphotransferase system, the following information about the regulation of the simultaneous synthesis of the galactose binding protein and the β-methylgalsotoside transport system was obtained. 1. Fucose acts as inducer for both the galactose binding protein and the transport system. 2, GalK mutants, endogenously induced with respect to the galactose operon, also show endogenous induction of the transport system. 3. The induction by fucose as well as endogenous induction is inhibited by 5 mM methyl-1thio-β-D-galctopyranoside. 4. GalR+, gale and galRs mutants can show full inducibility, excluding the function of gale in the regulation of the β-methylgalactoaide transport system. 5. Deletions of the entire galactose operon exhibit high yet inducible transport activities excluding the existence of a regulator gene near or in the galactose operon. 6. The existence of a regulator gene mglR which is different from galR, melR lacI, araC or pts could be demonstrated. The mutation mglR was found to he located between the origin of two Hfr strains, AB313 and KL16, i.e. between 56 and 74 min on the linkage map of E. coli. 7. Mutants defective in enzyme I activity of the phosphoenolpyruvate-dependent phosphotransferase system exhibit unimpaired β-methylgalactoside transport activity excluding any function of the β-methylgalactoside permease as a specific enzyme II of the phosphotransferase system. [ABSTRACT FROM AUTHOR]