bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium and phosphorus metabolism in the grey-lethal mouse
Authors: Murphy Helen M. 
Published: September 2009

Ca and P metabolism in the grey-lethal mutant mouse has been investigated. This animal is hypocalcaemic and hypophosphataemic and the serum alkaline phosphatase is elevated far above the normal. Increased bone ash content has been attributed to an elevated bone Ca. Fromin vitroexperiments involving steady-state distributions of calcium and phosphate it is concluded that active bone metabolism is reduced in mutant bone. This reduced ratio may be attributed to an increased passive ion solubility.These results tend to the assumption of an hormonal imbalance in this mutant system. An increased production of thyrocalcitonin has been postulated to account for these findings.
The effect of repeated cycles of selection and regeneration in populations of finite size
Authors: Curnow R. N. , Baker L. H. 
Published: September 2009

Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population are used to develop an iterative method for studying the effects of repeated cycles of selection and random mating. This is done by assuming a particular, but flexible and probably realistic, approximate form for the distribution of gene frequencies at each generation.The method gives for each generation the first two moments of the gene frequency distribution, the expected gain from selection, the probabilities of fixation and also the variability of gain. The variability of gain is of considerable importance in evolution, selection experiments and in plant and animal breeding programmes.Kojima's (1961) formulae have been extended to allow for differentiation between males and females. Hence different selection intensities and population sizes for the two sexes can be studied. Selfing with selection is considered separately. Extensions to cover simple examples of multiple alleles, linkage and epistasis are possible. Reference is made to previous work using transition matrices.
Genetic variability maintained in a finite population due to mutational production of neutral and nearly neutral isoalleles
Authors: Kimura Motoo 
Published: September 2009

1. The average and the effective numbers of alleles maintained in a finite population due to mutational production of neutral isoalleles were studied by mathematical analysis and computer simulation.2. The exact formula was derived for the effective number (ne) of alleles maintained in a population of effective sizeNe, assuming that there areKpossible allelic states and mutation occurs with equal frequency in all directions. If the number of allelic states is so large that every mutation is to a new, not pre-existing, allele, we havene= 4Neu+1 − 2Neu2, whereuis the mutation rate. Thus, the approximation formula,ne= 4Neu+1, given by Kimura & Crow (1964) is valid as long as 2Neu2≪ 1.3. The formula for the average number of alleles (na) maintained in a population of actual sizeNand effective sizeNewas derived by using the method of diffusion approximation. If every mutation is to a new, not pre-existing, allele, we obtainwhereM= 4Neu. The average number of alleles as a function ofMandNis listed in Table 1.4. In order to check the validity of the diffusion approximations, Monte Carlo experiments were carried out using the computer IBM 7090. The experiments showed that the approximations are satisfactory for practical purposes.5. It is estimated that among the mutations produced by DNA base substitutions, synonymous mutations, that is, those which cause no alterations of amino acids, amount roughly to 0·2–0·3 in vertebrates.Incompletely synonymous mutations, that is, those which lead to substitution of chemically similar amino acids at a different position of the polypeptide chain from the active site and therefore produce almost no phenotypic effects, must be very common. Together with synonymous mutations, they might constitute at least some 40% of all mutations. These considerations suggest that neutral and nearly neutral mutations must be more common than previously considered.
The genetic control of antibody production. A study of isoimmune antibodies in cattle twins
Authors: Sellei J. , Redel J. 
Published: September 2009

1. The antibody response was studied in twenty-five monozygous (MZ) and ten dizygous (DZ) pairs o f cattle twins, which were inoculated with red cells from one cattle donor carrying the M, V and U′ antigens. These red cell antigens are controlled by genes at three different loci. Most o f the recipients lacked two or all of these antigens. All had passed puberty at the onset of the experiment.2. The antibody response against the three antigens differed markedly. Anti-U′ appeared on the average 11 days after the 1st injection and the maximum titre values were high. The V antibodies were produced at a slow rate, while anti-M was intermediate.3. There was some influence of age on the rate and intensity of antibody production. Older animals gave a faster response and, with regard to anti-M, also higher titres.4. Twins belonging to the same MZ pair usually produced v e r y similar antibody curves. However, there was at least one noticeable exception, which is given special consideration in the Discussion. The differences between MZ pairs accounted for a considerable portion of the variance in the different measures of antibody response and in most cases this portion remained significant also after the elimination of the influence o f age and sex. The DZ pairs were more variable.5. The simultaneous response o f two or three antibodies in the same animal was studied. There was a significant positive association between antibody types which suggests the existence o f individual (probably genetic) differences in the general antibody-producing ability.
Genetic variation in the eel: I. The detection of haemoglobin and esterase polymorphisms
Authors: Pantelouris E. M. , Payne R. H. 
Published: September 2009

Electrophoretic studies on starch gel demonstrated the existence in the European eel of four haemoglobins, not two as believed from agar gel studies. The two minor fractions have been shown to be neither polymers nor methaemoglobin derivatives of the two principal fractions.The esterase zymograms of eel sera exhibit up to eight fractions. The individual differences observed suggest genetic polymorphism and the same applies to the esterase pattern of various tissues.This approach is of value for the collection of phenotypic frequency data with a view to solving the Atlantic eel problem.
Multistep transduction of tryptophan (trp) genes inEscherichia coli
Authors: Gratia J. P. 
Published: September 2009

Plaque-forming transducing (pt) particles of bacteriophage ø 80 have been used to transduce genes governing tryptophan synthesis. Main interest was devoted to strains which carry deletions extending for varying distances into the tryptophan (trp) operon, coveringtrp Aand ending intrp B,trp Cor further. If the deletion does not over-reachtrp C, infection byptparticles carrying thetrp(CBA)+segment gives rise to stable partial diploids which express the complete tryptophan independence. If the deletion is further extended, transductants are not entirely complemented and appear only on medium containing indole. If the recipients do not carry any prophage in the attachment site of ø 80 (att80) the indole-requiring transductants are very unstable; if the recipients do carry such prophage, even defective, all transductants are very stable. Stable indole-requiring diploids can be superinfected by otherptphages carrying the complementary genes of the tryptophan operon, giving rise to supertransduced indole-independent bacteria. Transduction to complete independence of tryptophan or any precursor has also been achieved in three steps. Supertransductants yield after u.v. inductionptphages carrying the initialtrpsegments and segregate rare cells with incomplete ability to synthesize tryptophan. They are therefore polylysogenic polyploid heterogenotes carrying overlapping segments of thetrpoperon linked to prophage genomes.When recipients are carrying a prophage inatt80, transductants appear at a low frequency. The reduction is particularly pronounced with ø 80pttransducing segmenttrp(CBA)+to immune bacteria.
The comparison of closely related groups of rodents by DNA/DNA annealing
Authors: McLaren Anne , Walker P. M. B. 
Published: September 2009

Within the genus Apodemus, DNA from A. sylvaticus and A. flavicollis could be distinguished on the basis of reciprocal DNA/DNA annealing in agar, even when unfractionated DNA was used. In preliminary experiments, DNA from geographical races of A. sylvaticus could not be distinguished, nor could DNA from two closely related species of Peromyscus.Within the species Mus musvulus, the fast-renaturing fraction of L-cell DNA, separated on a hydroxyapatite column, was able to discriminate between L-cell (originating from the C3H inbred strain) and NZB (New Zealand Black) inbred strain DNA in agar.
The introduction of genetic material from inferior into superior strains
Authors: Osman H. El Sayed , Robertson Alan 
Published: September 2009

1. A series of experiments have been carried out withDrosophila melanogasterin order to improve further a population, highly selected for a quantitative character, by introducing genetic material from an inferior population. The effects of selecting the latter before crossing to the selected line, of waiting after crossing before restarting selection and of varying the intensity of selection after crossing have been studied. The inferior population used was the large random breeding population from which the selected line had been produced by selecting downwards for sternopleural bristles.2. There proved to be some incompatibility between the conditions necessary to achieve the two criteria of success—the time to surpass the selected line and the extent by which it was eventually exceeded. The lines which surpassed it soonest had not been selected before crossing and had been selected intensely immediately afterwards. Those which surpassed it most had had the greatest amount of selection before crossing followed by the most intense selection afterwards.3. Crossing-over did not appear to be a limiting factor after crossing. Neither a period of relaxation after crossing nor a lower intensity of selection after crossing increased the chance of success.4. Genetic analyses were made of several lines which had exceeded the original selected line. In separate lines, second, third and fourth chromosomes were found which were superior to the chromosomes of the selected line. This and other evidence shows that the limits in such lines with a small number of parents are not in any way absolute but artefacts of the selection programme. The extreme third and fourth chromosomes were both recessive to that of the selected line in the effect on bristle score.5. A theoretical discussion of such selection programmes is given, assuming that the character is controlled by independently segregating loci. It is shown that, if two alleles at different loci have an equal but small chance of fixation in the initial selection, one because it is rare and the other because, though frequent, it has little effect on the character, such a programme will tend to pick up the former rather than the latter. Of two such rare alleles with an equal initial chance of fixation, the one additive and the other recessive, the chance of fixation of the latter will be greater in a crossing programme.
The effects of population size and selection intensity in selection for a quantitative character inDrosophila: I. Short-term response to selection
Authors: Frankham R. , Jones L. P. , Barker J. S. F. 
Published: September 2009

1. The response to selection for increased number of bristles on one abdominal segment was studied over 12 generations using a factorial design of three population sizes (10, 20 and 40 pairs of parents) and five selection intensities (10, 20, 40, 80% and controls).2. The responses on the average agreed well with those expected from the estimated base population heritability, but individual replicates diverged considerably.3. Larger populations tended to give greater response to selection, due mainly to larger realized heritabilities.4. There was no consistent effect of selection intensity on realized heritability.5. For populations with the same number of individuals scored, less intense selection gave greater realized heritabilities.
The effects of population size and selection intensity in selection for a quantitative character inDrosophila: II. Long-term response to selection
Authors: Jones L. P. , Frankham R. , Barker J. S. F. 
Published: September 2009

1. An experimental evaluation of Robertson's (1960) theory of limits in artificial selection was attempted. A number of lines from the Canberra base population were selected for abdominal bristle number over 50 generations with population sizes of 10, 20, and 40 pairs of parents and selection intensities of 10, 20 and 40% as well as unselected controls.2. In general, the total response obtained increased with an increase inNī(product of population size and standardized selection differential).3. Thus, total response increased with increase in the number of individuals scored, or, for a fixed number of parents, increase in selection intensity increased both rates of response per generation and total response.4. But for the same total number scored, the response increased as selection intensity decreased. However, the proportion selected had only a small effect as compared with that of the total number scored.5. Sublines in which the population size was reduced after 16 generations of selection but with the selection intensity kept constant, immediately fell behind their parent lines and gave much less response.6. Agreement between replicate lines was generally poor, particularly for the 10- and 20-pair lines.7. Patterns of response in individual lines were frequently irregular and ‘waves of response’ were not uncommon.8. The results are discussed in terms of several theoretical models of selection limits. In general, agreement with these models was poor, as much of the response appeared to be due to a few genes (or gene combinations) with large effects on bristle number.
Growth rate and haploidization ofAspergillus nigeron medium containingp-fluorophenylalanine
Authors: Lhoas Pol 
Published: September 2009

1. The comparison of the dry weight of thin layer haploid and diploid colonies ofA. nigeron complete medium and complete medium supplemented withp-fluoro-phenylalanine led to the conclusion that there is a difference in growth rates of hyphae under these different conditions.2. The growth curves of the same strains on both media were established. On complete medium, haploids and diploid show a growth rate increasing linearly for about 20 h after germination and reaching a maximum which is then maintained. Onp-fluorophenylalanine, the haploids show a similar curve, although the maximum growth rate reached and maintained is about half that on complete medium; for the diploid, however, the maximum is less than the corresponding one in the haploid and, once this maximum has been reached, the growth rate goes down linearly to a very low value which is then maintained.3. The cytological study of the hyphal tip cell showed, in the presence of the amino acid analogue, a reduction of the mean size of the diploid nuclei together with an increase of the number of nuclear fragments. This explains the growth rates observed and is accepted as a confirmation thatp-fluorophenylalanine, by its action on the mitosis, favours chromosome losses which lead finally to the production of haploid nuclei.
Aegilops×Secalehybrids: the production and cytology of diploid hybrids
Authors: Majisu B. N. , Jones J. K. 
Published: September 2009

SUMMARYHybrids between four diploid species ofAegilopsand species ofSecalewere obtained by using embryo culture. There was a marked incompatibility in the crosses betweenSecalespecies and each of the four species in Section Sitopsis ofAegilopsandAe. mutica. It is suggested that this genetic incompatibility withSecalespecies is an additional similarity between these species ofAegilopsand the diploid species ofTriticum.Most chromosomes ofAegilops(A) andSecale(S) are univalent during meta-anaphase of meiosis in these hybrids, but some appeared to associate and others to pair as apparently normal chiasmate bivalents. Analysis of non-chiasmate and chiasmate associations showed that the frequencies of autosyndetic (AA and SS) and allosyndetic (AS) associations fitted the 3AA: 7AS: 3SS ratio expected if association and pairing is at random. Any deviations from random involved a deficiency rather than an excess ofAegilops-Secalepairing. There is no evidence that the chromosomes ofSecaleare homologous with those ofAe. caudata,Ae. comosaandAe. umbel-lulata, and it is suggested that the genome ofSecalespecies does not show any homology with the genomes of the generaAegilops. This does not preclude the presence of homologous segments. It is suggested that the possibility of random association of chromosomes should be considered when occasional pairing in interspecific hybrids is analysed, and that identification of chromosomes and recognition of chiasmata are required. The possibilities of chiasmata between non-homologous chromosomes, of a genetic mechanism in rye which suppresses the pairing of homoeologous chromosomes, and of other factors causing asynapsis and pseudo-synapsis between genetically similar chromosomes are discussed.
Genetical and structural analyses of cell-wall formation in Chlamydomonas reinhardi
Authors: Davies D. Roy , Plaskitt A. 
Published: September 2009

SUMMARYFifteen mutant strains of Chlamydomonas reinhardi were isolated which showed defects in some aspect of the process of cell-wall formation. Genetic analyses indicated that most of the mutations were due to single gene changes; two were anomalous in that non-Mendelian segregations were obtained on crossing with other genotypes, and on selfing they frequently gave rise to wild-type phenotypes.Occasional somatic revertants were also obtained from these two strains. On the basis of these analyses it is suggested that there are two levels of control operating in the process of cell wall biogenesis - one concerned with subunit production at the nuclear level and another, possibly concerned with three-dimensional organization, at another level. Electron-microscope analyses of the different mutants showed the mutants to be divided into three main categories: those in which the wall was formed but was not attached to the plasma membrane, those in which the wall was attached to the membrane, and those in which very little wall was formed. In the last class in particular, vesicles containing wall precursors were clearly visible, and were shed through the plasma membrane into the medium.
Gene conversion: remarks on the quantitative implications of hybrid DNA models
Authors: Gutz Herbert 
Published: September 2009

SUMMARYSome quantitative implications of the gene conversion models of Holliday and Whitehouse & Hastings are discussed. These models predict two kinds of mispairing when a heterozygous mutant is in hybrid DNA. It is pointed out that the latter model, in contrast to statements in the literature, does not require identical repair rates in both kinds of mispairing.Furthermore, some peculiarities are discussed which result if, among the corrected fractions of hybrid sites, the frequency of repair to wild-type is the same in both kinds of mispairing (r=s). In the Holliday model a minimum results under this condition for the frequency of asci which show a normal 4:4 segregation, but which have originated by repair from meioses with hybrid DNA.
A genetic analysis of therudimentarylocus ofDrosophila melanogaster
Authors: Carlson Peter S. 
Published: September 2009

SUMMARYA study of the structural and functional organization of therudimentary(r: 1–54·5) locus ofDrosophila melanogasterhas demonstrated that alleles of this gene reside in a number of recombinationally separable sites, and display a complex pattern of interallelic interaction. Data relating to interallelic interaction have been utilized to construct a linear complementation map consisting of 7 complementation units and 16 complementation groups. Comparison of the genetic fine structure map and the complementation map shows that the two maps are approximately co-linear. Totally non-complementing alleles reside at both ends of the fine structure map. Therlocus is best interpreted by the model of a single cistron whose product affects several distinct developmental processes and whose alleles display a complex pattern of interallelic complementation. Intragenic recombination within therlocus is accompanied by the appearance of parental and recombinant flanking marker classes not expected on the basis of reciprocal recombination. Studies with half-tetrads demonstrate that intragenic recombination can occur either by gene conversion or by a reciprocal exchange mechanism. The pattern of organization seen at therlocus is similar to patterns of organization found in work with fungal genes.
Evidence for allelism of leaner and tottering in the mouse
Authors: Tsuji Shigekatsu , Meier Hans 
Published: September 2009

SUMMARYWe found thatlais located in linkage group XVIII. It is highly probable thatlaandtgare alleles, and closely, linked toEs-1. Mice of the genotypela/tgare abnormal, with clinical signs similar totg, although more severe. They develop earliest signs at about 15 days of age, similar tola, are runted but fertile and can live for months. Clinical signs are ataixa, stiffness, retarded motor activity and intermittent focal seizures. The pathological basis for these symptoms is still elusive. The three types of mice,la/la,la/tgandtg/tgare thus distinct clinically,la/tgresembling in some respect either of the other two.
The highly polarized recombination pattern within the methA gene ofAspergillus nidulansRecombination within the methA cistron ofA. nidulans
Authors: Putrament Alexandra , Rozbicka Teresa , Wojciechowska Katarzyna 
Published: September 2009

SUMMARYThe recombination between the methA alleles ofAspergillus nidulansis very strongly polarized. The mutants can be mapped in respect to each other and in respect to the flanking markers, both on the basis of the relative frequency of one of the P classes and one of the R classes. In all crosses it is the distal mutant which converts predominantly.In one combination of the mutants crossed the low temperature at which meiosis proceeded increased recombination frequency and modified the recombination pattern.
Salmonella hybrids containing genic material of multiple origins
Authors: Armstrong F. B. , Sprague George F. 
Published: September 2009

SUMMARYBacterial hybrids were produced to contain genetic material ofSalmonella typhimurium, Escherichia coli, S. montevideoandS. abonyorigins. Analyses by transduction provide evidence that 6% of the originaltyphimuriumgenome has been replaced in the production of these hybrids. Although a number of biosynthetic pathways are affected by this gene substitution, the growth rate of these hybrids in minimal medium is unchanged. Supporting evidence for the close relatedness betweenS. typhimuriumand the other three species is not observed in recombination studies. Available results favour the concept that differences in base sequences are responsible for the low frequency of recombination obtained in heterologous crosses.