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A procedure to isolate Escherichia coli mutants defective in ribonucleotide reduction is described. Using a parental strain defective in dCTP deaminase (paxA) and thus unable to synthesize dUMP from deoxycytidine nucleotides, we selected for cells unable to reduce UDP at a rate sufficient to satisfy the cell's need for thymidine nucleotides. This was accomplished by selecting for cells resistant to 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (trimethoprim) in the presence of thymidine and screening these cells for a thymidine requirement that could be satisfied by deoxyuridine. Genetic analysis as well as enzyme assays of four such mutants chosen for study indicated that three had a defective thymidylate synthetase. One, LD195, which had normal thymidylate synthetase activity, was found to have a conditional deoxyuridine requirement that is only expressed under favourable growth conditions. Since restoration of a functional dCTP deaminase to derivatives of LD195 eliminated the deoxyuridine requirement, it was concluded that a combination of two mutations is responsible for the expression of this phenotype. Analysis of nucleotide pools of LD195 grown exponentially under permissive conditions revealed that both the dTMP and dTTP pools were 6-fold lower than in the parent indicating a deficiency in the production of a thymidine nucleotide precursor. Enzyme assays of crude extracts of LD195 indicated that this deficiency was due to a defective ribonucleosidediphosphate reductase. This conclusion is proven by an extensive enzymatic analysis presented in an accompanying paper. [ABSTRACT FROM AUTHOR]

The article presents a paper discussing chromosomal mosaicism in two Japanese children with Down's syndrome. The first case was of a six year old boy whose first dentition was at 16 months and first steps at two years ten months of age. A physician noticed retardation of mental and physical development at age three. The physical symptoms revealed an atypical case of Down's syndrome. Mental age at the age of six was about two years. The second case was a five-year-old female, who was delivered by Caesarean section.

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 presents a study related to the ability to differentiate characteristics between the sexes cosmetically, structurally, anatomically and psychologically of decided importance in the sex adjustment of the individual. In studying a level of genetic development in children, it is important to obtain facts supplied by the children themselves, if possible. To do this, one must use methods for meeting children on their own level of expression. Projective methods, generally, and drawings of children, specifically, have been successfully used to study personality development and deviations. Like the boys, socio-economic level is probably related to the number of covert characteristics drawn by girls.

The article provides information about polytypism, monotypism, and polymorphism. The three suggests that a monotypic species may have a single type with insignificant variation. Polytypic species, according to zoologists, is defined as one that is divided into formal sub-species and monotypic species. Polymorphism is a form of variation within single populations. It does not include all intrapopulational variation but only such variations as are hereditary and confined to a few sharply distinct states. It depends on the occurrence in a genetic pool of one or few genes with two or more alleles sharply distinct in their effects.

The article discusses the right-or-left-handedness of human beings in terms of genetics and heredity. A vast area of biological theorizing and interpretation revolve around hereditary. Mendelian theory had detected genes and chromosomes to be responsible for various characteristics of human beings. The use of hand by a human being is decided by the difference in development of a portion of his brain. It has been experimentally established that the portion of brain which grows earlier in embryonic life dominates the actions of matured body. Also is the fact that what one does and the way of doing is dominated by the hand used.

Excised primary roots of Phaseolus vulgaris L. were treated with canavanine and the effect on arginine utilization was studied. Arginine utilization was observed to be depressed to a low level by canavanine (1.8 × 10-4 M) in rapidly dividing and growing tissues. In addition, canavanine inhibited at ginine utilization to a lesser degree in root sections composed of mature and non-dividing tissues. This demonstrated that canavanine inhibition is not limited to those tissues where active DNA synthesis occurs. Canavanine was observed to inhibit the onset of mitosis in primary roots as evidenced by a significant reduction of the frequency of mitotic figures. In addition, this amino acid was found to affect the course of mitosis once it was initiated by altering the relative frequency of mitotic stages, decreasing the percentage of prophase figures and increasing the percentage observed in the telophase. An influence on the rate of spiralization and despiralization of the chromosomes is suggested. The effects on mitosis are probably related to growth-inhibitory and toxic effects of canavanine. The possible function of canavine as an allelopathic substance is hypothesized. [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]

The article reports on polymorphism and natural selection. It states that there was a small outbreak in the literature which appeared in "American Naturalist," occasioned by the criticism of Oxford zoologists P. M. Sheppard and A. J. Cain as well as the claim made by T. Dobzhansky in his book "Genetics and the Origin of Species." The author mentions the three points made by Sheppard and Cain. One of which is that while admitting that if polymorphism within a breeding community increases the efficiency of the development of the resources of the environment then polymorphic organisms could be considered as better adapted than monomorphic ones.

The article discusses the limits of the genus Eleocharis that will be added in the species E. pauciflora. The genus may be defined as a group of plants allied to Scirpus, but different in the possession of a single terminal ebrateate spike on a haulm bearing leafless sheaths and a fruit with distinctly differentiated and often swollen style-base. The genus contains six British species as defined by Svenson. It is inferred that the two species are closely related but are normally satisfactorily separable on a few morphological characters.

The article reports on the marine ecologist's investigations regarding most animals and plants. It highlights the research on the animals and plants, which reduced to invisibility and immersed in an intermixed soil and subsoil, are transported from here and there by wave, tide and current. It also highlights the all animal species in the heterogeneous assemblage, called plankton and the rise and fall throughout the depths in differential ways. It says that the ecologist finds difficulty in describing and finding the species. Furthermore, the ecologist's knowledge of the interrelationships among plankton organisms due to food and enemies coincidence of life-cycles, and behavior relative to weather and hydrographic conditions have a scientific significance.

The ability of C57BL, C3H, and A strain marrow cells to proliferate on transplantation into irradiated isogenic, F1 hybrid, and backcross progeny mice has been investigated by the spleen-colony technique and by measuring the newly-formed DNA in the recipient spleen with [131I] 5-iododeoxyuridine. Transplants of C57BL cells grew poorly in (A × C57BL) F1 and in (C57BL × C3H) F1 and reciprocal hybrids, as compared with isogenic and allogeneic hosts, whereas C3H and A strain marrow grafts were successful in isogenic, F1 hybrid and backcross recipients. In segregating backcross progeny, i.e. in offspring from F1 hybrid females mated to C57BL males, the frequency of success or failure of the C57BL grafts suggested that the trait was controlled by a single pair of genetic determinants at an autosomal locus. The latter is apparently linked with, or part of, the H-2 region in the IXth linkage group. The experimental evidence suggested also that the failure of C57BL haemopoietic cell grafts in H-2 heterozygotes was not related to exhaustion of donor cells by excess of recipient isoantigen but rather to lack of expression in the heterozygotes of histocompatibility-related growth requirements yet undefined. These requirements are specific for haemopoietic cells, but not for skin grafts, and resulted most probably from the effect of genetic (inter-allelic) interaction involving H-2 or an H-2-linked locus. [ABSTRACT FROM AUTHOR]

The action of partially purified enzyme preparations from Trichomonas foetus on the serological properties of the water-soluble A, B, H and Lea human blood-group substances has been examined. Further evidence has been obtained for the presence in A and B substances of structures closely similar to, or identical with, the specific determinant groupings in H substance. In addition, it has been shown that enzymic destruction of H serological properties results in certain instances in a considerable increase in the reactivity of the H substance with Lewis anti-Lea sera. The capacity to develop Lea specificity appears to be related to the Lewis blood-group phenotype of the individual from whom the H substance is derived. The significance of these results is discussed in relation to schemes which were put forward earlier for the biosynthesis of the blood-group mucopolysaccharides. [ABSTRACT FROM AUTHOR]

The Gm serum groups in man have been investigated serologically and genetically. Two populations have been studied. In Great Britain the frequency of the Gm (a+) phenotype is 60.98 per cent. In the Ferrara district of Italy the frequency is 40-18 per cent. Family studies in both populations support the hypothesis that the Gm (a+) phenotype is determined by a gene which is expressed in the heterozygote. [ABSTRACT FROM AUTHOR]

Nascent M12 RNA has been isolated in large quantities from Replicative Intermediate and denatured by a short heat treatment. After sucrose gradient centrifugation of the. denatured Replicative Intermediate in a zonal rotor, the nascent RNA strands were divided into six fractions with increasing sedimentation values. Each fraction was further purified by sedimentation conventional sucrose gradients. In this manner, a set of M12 nascent RNA strands with fairly uniform lengths, ranging from about 15 nucleotides to almost 90% of the complete phage RNA genome, have been obtained. The molecules in these fractions, all containing the same 5'-end as complete phage RNA but an increasing portion of the phage genome, provide suitable tools for studies of the structure and function of phage RNA. [ABSTRACT FROM AUTHOR]

The article presents hypothetical and realistic models in the teaching of genetics in elementary. It shows a series of educational devices of use for the realistic aspects of heredity which includes the illustration of heredity with the use of gamete formation. It discusses the distinction between Mendelian, genotype and phenotype ratios. It also mentions devices of use in testing for a hypothetical understanding of heredity. Having the students know the devices and the discussions, made them understand genetics easier, even without the complications of advanced mathematics, statistics and biology.

Four different descriptions of lateral asymmetry are reviewed and their probable interrelations examined. Two main features are distinguished: first, a normal distribution of relative efficiency of the two sides which probably applies to all species subject to lateral differences; second, a factor specific to humans which induces a shift of the normal distribution toward dextrality. A brief discussion of the origins of asymmetry leads to the conclusion that the basic normal distribution probably depends on accidental variation while the human shift to the right may be a product of both cultural and genetic influences. The latter could imply that human right handedness is inherited while left handedness is not. [ABSTRACT FROM AUTHOR]

Samples from a population of plants present in a grazed bill sward were isolated and grown as spaced individuals at a lowland site. The predominant taxa present were Agrostis, chiefly A. tenuis Sibth., and Festuca rubra L. Within each species, there was considerable variation between plants obtained from a relatively small area of sward. From an examination of morphological characters and tests of self- and cross-compatibility among plants, an indication of the number of genotypes present was obtained. Eighty-four putative genotypes of Agrostis and forty of Festuca were identified. A map is given showing the position of each putative genotype in the original population and the structure of Agrostis-Fesluca swards is discussed. [ABSTRACT FROM AUTHOR]

Open-pollinated seedling progenies of Eucalyptus obliqua grown in a uniform environment showed evidence of genetic variation among geographically different localities and among parent trees within localities. Locality variation did not appear habitat-correlated, so no predictor of a superior locality for tree-improvement purposes could be suggested, other than appearance of the trees; breeding strategy should include tree selection within localities. Several superior localities were indicated consistently but many showed marked fluctuations, suggesting the need for caution in interpreting seedling data. [ABSTRACT FROM AUTHOR]

The sizes and shapes of different parts of pyrenes obtained from two diallel crosses of raspberry were influenced both by maternal effects and by interaction effects involving maternal and genetic factors. The relative importance of these effects depended upon the environment in which the crosses were made. For a diallel made under field conditions interactions with maternal factors were large but considerably reduced by applying auxin to the developing fruits. For a diallel made in a glasshouse maternal effects were more important and maternal interaction effects less so. Application of auxin to the fruits reduced endosperm or embryo size in some crosses and increased it in others. It is postulated that these responses were related to the endogenous content of growth substances, negative responses indicating their presence in supraoptimal concentration, and that variations in the responses provide clues to the physiological factors which govern successful pyrene development. [ABSTRACT FROM AUTHOR]

The article discusses the subject of race as a group that is differentiated with inherited anatomical features and focuses on the study of human fossil, comparative anatomy and the methods of classification. The author analyzes the racial problems to clarify thinking about race in general. Topics discussed include the relation of the head form to race, the use of genetics for the classification of man, meaning of the words: race and species and methods of classification and pure races. The earliest racial classifications were based on grouping those that are alike one another on the basis of shared traits like color and hair form. The second stage was under the influence of Darwinian evolution and talked about the evolutionary history of man on the basis of anatomical comparisons. According to the author, race is not related to language, religion, nationality or social habits.

There is an inverse relationship between growth rate and IAA oxidase activity in the genetically determined growth types of the yellow lupine (Lupinus luteus L.) at the age of 5 to 25 days. Genetic constitution, however, has a smaller effect on enzymatic IAA destruction than on growth intensity. It is probable that genetic growth control is correlated with other metabolic processes associated with growth, e.g., endogenous gibberellin synthesis. IAA oxidase action ceases at the age of 25 days when the total phenol content in the above-ground parts of the plants attains a value of about 30 μg phenol/mg dry matter. This is followed by termination of the leaf-rosette stage in a wild form. [ABSTRACT FROM AUTHOR]

Three strains of tobacco tissue which, despite having a common origin, differ markedly in their requirements for exogenous plant growth substances are described. Kinetin (6-furfurylaminopurine) or its equivalent and an auxin such as indole-3-acetic acid are both required for the growth of normal tobacco pith tissue in vitro. However, a strain which requires only auxin and a strain which requires neither a kinin nor an auxin have been obtained. The latter, from which substances with auxin and kinetin-like activity can be extracted, differs markedly from normal tobacco pith in tissue culture with respect to chromosome number. The possibility that a specific chromosome complement is related to the biosynthetic ability of the tissue is discussed. [ABSTRACT FROM AUTHOR]

1. The gibberellins do not prevent the division of the root tip cells of Narcissus tazetta in concentrations between 20-200 p.p.m. during a 4-hr. to 10-day period of treatment. 2. The gibberellins induce the differentiated cells to divide in the roots of Narcissus tazetta. 3. The gibberellins do not affect the course of mitosis. 4. The gibberellins give rise neither to changes in the chromosomes nor to polyploidy. 5. Indole-3-acetic acid also compels the differentiated cells in the roots of Narcissus tazetta to divide. A bigger treatment, however, prevents the division of the root tip cells. 6. Indole-3-acetic acid gives rise to the enlargement of the cortical cells above the root tip. The gibberellins do not have this effect. [ABSTRACT FROM AUTHOR]

In four species of the family Umbelliferae a fundamental morphogenetic change, called neomorphosis, has been induced by critical concentrations of certain amino acids. The neomorphs of Oenanthe aquatica, reported previously in brief, have now been described in detail. In Oenanthe aquatica the neomorph pattern of growth induced by glycine could be sustained by various other amino acids, by two pyrimidine derivatives, and by an amine. It consists in a vegetative cycle of reproduction in which development is restricted within an embryonic range, commencing from callus-like nodules and leading, at the most, to individuals corresponding to cotyledon-stage seedlings but adapted to submerged growth. If amino acid is omitted but sucrose present, the neomorph pattern of growth may continue for several months, but eventually a transition to normal growth takes place by the formation of new growing points. Thus, In the species in question, neomorphosis does not involve any irreversible change of the genome. The transition to normal growth is considerably accelerated by ribose, although ribose inhibits growth in size. The results indicate that amino acids are closely concerned with differentiation. [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]

Two pyridoxamine-less strains, W 233-2 and W 366-10, of Ophiostoma mutliannulatum have been compared from physiological and genetical point of view. Both strains give a slow growth response to pyridoxal. For W 366-10 it has been shown that the response to this vitamin is influenced by the genetic back-ground. In contrast to the other mutant, W 366-10 grows with pyridoxine at 20 °C but not at 30°C,. It is thus temperature-sensitive. An intercross between the mutants revealed that the genes responsible for the pyridoxamine-less character are non-allelic and closely linked, or possibly pseudo-alleles of the same gene. A spontaneous mutation to pyridoxal-heterotrophy, W 366-10-1. lias been found in a population of W 366-10, pyridoxamine-less. The acquired pyridoxal-less character is conditioned by a suppressor gene. Pyridoxal-less strains have been .synthesized by combining W 233-2 and W 306-10 with a prototrophic reversion of W 366-10-1. The suppressor gene bas no observable phenotypic effect except the above mentioned. [ABSTRACT FROM AUTHOR]

Relationships between crystal chemistry and genetic conditions are presented for a series of dioctahedral micaceous minerals. Using a ferruginicity index, three groups of micaceous minerals are distinguished: Al-micas, Fe-illites, and glauconites. The degree of Al-for-Si substitution in the tetrahedral sheets of micaceous minerals depends on their thermodynamic genetic conditions. If pressure and temperature increase, the A1-IV content increases and the octahedral sheet is ’cleaned’ from divalent cations. This process is accompanied by structural alteration with a polytype sequence 1M[suba]−1M−2M[sub1]. Tetrahedral and octahedral charges are the same for micaceous minerals formed at the surface (sedimentogenesis/diagenesis) and are independent of the iron content. For most illites of sedimentary rocks an authigenic origin is suggested. [ABSTRACT FROM AUTHOR]

Individual differences in social introversion-extraversion were examined in a large sample of twin girls and found to be highly heritable. Genetic factors accounted for more than half of the within-family variance, measured by Gough's Adjective Check List and the Fels Behavior Scales. The results for this population support previous studies by Gottesman, Eysenck, Vandenberg, Freedman, and others, who reported similar heritabilities for social introversion, extraversion in other populations, tested with other measures. Several longitudinal studies have reported consistent individual differences in sociability, which may be explained by the large genetic contribution to the dimension. Both longitudinal and twin data suggest that social introversion-extraversion is a basic way of responding to the environment, produced by polygenic inheritance and environmental interaction. [ABSTRACT FROM AUTHOR]

A study of 61 pairs of identical (MZ) and fraternal (DZ) grade-school twin girls found moderate genetic contributions to individual differences in several aspects of activity motivation: reaction time, variety of activity, anxiety, and impatience. Activity motivation was defined by empirical clusters of related measures including ratings, experimental tasks, and interviews. Intraclass correlation coefficients for the MZ and DZ groups were compared, and heritability estimates were computed for every measure. Possible biases in twin research were examined with special emphasis on the environmental similarity of MZ and DZ co-twins. [ABSTRACT FROM AUTHOR]

Focuses on the trends in the study of physical growth in children. Features of the standardization study of physical growth; Interpretation of anthropometry from a biological viewpoint; Assessment of the hereditary transmission of physical characters.

1. Asynapsis of the salivary chromosomes of D. funebris is analyzed in 50 chromosomes of each kind in 10 strains and in 9 crosses with the L strain. The percentage of asynapsis is calculated by measuring the distances in the standard map of the salivary chromosomes (PERJE, 1954). Diagrams of the asynaptic regions are given. In the X-chromosome asynapsis is greater in the crosses than in the pure strains. It is mainly localized in the proximal heterochromatic region. The autosomes show very intimate pairing in both the strains and crosses, 2, A more thorough investigation of the pairing tendencies in the proximal heterochromatic section of the X-chromosome shows that the partners are more often unpaired in the crosses than in the pure strains. This indicates homologous pairing of the heterochromatic regions, 3. Short inversions, probably depending on duplications of the type abba are described for chromosomes 4 and 5. 4, These duplications or inversion heterozygotes are assumed to aid the species to retain a great variability in the gene pool, a condition which is typical for the species. [ABSTRACT FROM AUTHOR]

As selection is an irreplaceable method in animal and plant breeding it certainly is of great importance to furnish as broad as possible a basis of experiences and observations concerning it. Furthermore the aims of laboratory selection experiments are numerous and variable. The present investigation primarily concerns the consistency and inconsistency between responses to selection from unrelated strains. As decisive characters two types of bristles have been used. The mean, the variation and the range of phenotypical expression have been recorded and also the influences of selection on other characters, as such correlated changes may reveal physiological connections that cannot otherwise be stated.

1. Brother-sister matings were made from a pair culture in the W strain of D. funebris with the sex ratio 0.502. There was a normal frequency distribution of sex ratios, showing no sex-linked lethals in the system. 2. Brother-sister matings from a pair culture of the y v sn zv stock of D. funebris with the sex ratio 0.498 gave no deviations from the normal sex ratio distribution other than should be expected from the lower viability of the mutant hemizygous males. The sex ratios in the original strains from which the mutant stock was built up were abnormal. 3. Selection for high sex ratios was made in four lines of the M strain of D. funebris. The generation mean increased significantly. Only slight differences could be found between the generations. In the series MB III b and MB IV b the balanced polygenic system was broken up and showed a spread of sex ratios from about 0.5 to nearly I.O with two obvious maxima in MB IV b, one at about 0.52 and the other at about 0.86-0.88. 4. The frequency distribution in MB IV b (fig. 3) shows that sex-linked lethals in the Y-homologous part of the X must be a part of the system. Such sex-linked lethals cannot be the only cause of the abnormal distribution, as with such a system no theoretical sex ratio values should be expected between 0.50 and 0.67. Thus there must be an interaction between the sex-linked lethals in the Y-homologous part of the X and lethals in some other part of the chromosome set. As the mechanism appears partly to be due to duplicate factors and partly to linked complementary gene actions the author has proposed the hypothesis that duplicated segments may be the cause of this phenomenon. One of the segments should lie in the X- and the Y-chromosomes and the other in one of the autosomes, or possibly be inserted in the non-homologous part of X. Homologous gene pairs would act as duplicate factors and different lethals within a segment as linked complementary factors. 5. Such a balanced system of lethals will cause many adjacent recessive mutations to retain their heterozygous condition, which Mall give a gene mechanism that combines uniformity of the species with a high degree of heritable variation. This will give a possible explanation of the accumulation of modifiers which is a characteristic of the species. [ABSTRACT FROM AUTHOR]

Drosophila funebris FBR. has been used in genetical, cytogenetical and cytological investigations of different kinds in many genetic laboratories. In the laboratory, D. funebris breeds readily on the same cornmeal-syrup-agar culture medium as D. inelanogaster. To maintain the strains, the flies were reared in milk bottles. In experimental cultures,--pair cultures or mass cultures--the flies were reared in small vials in order to facilitate handling and to save space. A block of cornmeal-syrup-agar were laid upon a piece of cardboard and placed in the vial.

The article discusses the origin and history of the germ cells in the ubiquitous English sparrow, Passer domesticus. There is, perhaps, no non-migratory bird of the order Passeres that has a wider range of distribution than has Passer domesticus. Indigenous to the British Isles, it has, aided by the agencies of man, become distributed over nearly all parts of the earth. The English sparrow is extremely prolific. Normally, from three to four broods are reared during the long breeding season, extending from early April to late July. The number of eggs in a clutch is usually five, less frequently three, four, or six. The eggs vary greatly in size and coloration. The normal type may be described as whitish gray thickly marked with clark gray or olive blotches, and approximately two by one and one half centimeters in size. Incubation does not begin until shortly before the full clutch of eggs has been laid.

This article contains the results of two different investigations that deals with the question of the, causes for the varying percentages of exceptions in different non-disjunction cultures of Drosophila melanogaster. The article also treats of some of the connections arising between the two species of Drosophila, Drosophila melanogaster and Drosophila simulans. For carrying out these researches the author have been chiefly dependent on access to various cultures of Drosophilae. The author have been able to procure the same partly through O.L. Mohr, a professor of the University of Kristiania, partly through A.H. Sturtevant of Columbia University, New York, to both of whom the author begs to tender his sincerest thanks for their obliging assistance. On glancing back at the development made in research on the laws of heredity during the short period, scarcely two decades, of their existence, it is first and foremost necessary to note the vast number of investigations carried out, and the enormous amount of evidence which has been collected in regard to some of the fundamental principles of genetics.

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]

The various stages of M 13 DNA replication were investigated in an Escherichia coli dnaE mutant thermosensitive in DNA polymerase III after a shift to the restrictive temperature (45 °C). The following results were obtained. (1) DNA polymerase III is not needed for the conversion of the infecting single-stranded phage DNA into the parental replicative form. (2) Semiconservative replicative form replication is completely blocked in the absence of a functional DNA polymerase III. (3) Synthesis of phage-specific DNA continues after a temperature shift late in the infection. However, due to an inherent thermosensitivity of M 13 single-stranded circular DNA production no free single strands are detected. [ABSTRACT FROM AUTHOR]

In Escherichia coil K 12 either of the two genes argF and argI is able to produce a functional ornithine carbamoyltransferase. When both are active in the same cell the two gene products interact to form a family of four hybrid trimeric isoenzymes of undistinguishable molecular weights, a situation presently unique th bacteria where very little genetic redundancy seems to occur. In E. coli B and W only the I gene product is found. Evolutionary implications of the structure and the genetic control of ornithine and aspartate carbamoyltransferase are discussed . [ABSTRACT FROM AUTHOR]

The article features relevant and irrelevant issues in development. An illustration of the manner in which current behavior theories permit and encourage the introduction and investigation of developmental variables in the cognitive behavior of the child is discussed. The concept of development has been used to name those changes in behavior that normally occur with an increase in the chronological age of the child. The developmental changes to an increase in chronological age or to "growing older" are attributed to common sense. Students of child behavior sought explanations in physiological changes, in experience, and in genetically determined characters.

Within the pointer breed of dog two strains have been developed by selective mating and line breeding. The goal is that of producing behaviorally distinct stable and unstable (nervous) strains to measure hereditary effects including dominance and sex Unkage, if present, Some behavioral difference emerged early. Measures of operant conditioning and other behavioral tests have little overlap. We conclude that genetic controls are important for behavioral research, even within a single breed, and that temperamental variables have strong genetic factors as well ss environmental ones. [ABSTRACT FROM AUTHOR]