bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mathematical study on the distribution of the number of repeated genes per chromosome
Authors: Takahata Naoyuki 
Published: September 2009

SUMMARYI develop a mathematical model which can account for a distribution of the number of repeated genes per chromosome under the joint effects of sister chromatid exchange (SCE), inter-chromosomal crossing-over (ICC), and selection. The model can be applied not only to the cases of small gene clusters but also to multigene families. Based on this model, an appropriate mathematical formula is derived and used to obtain the equilibrium distribution. Assuming stabilizing selection and two simple schemes concerning SCE and ICC, I numerically calculate the equilibrium distribution and compare the result with observations on frequencies of single and triple α-haemoglobin genes in primates. It is also shown that if SCE and ICC occur according to the same probabilistic law, the distinction between them does not make much sense in the equilibrium distribution.
Direct and correlated responses to selection for plasma thyroxine levels in mice
Authors: Tilakaratne N. , Hill W. G. , Land R. B. 
Published: September 2009

SUMMARYSelection was carried out in mice for concentration of thyroxine hormone (T4) in plasma of males at 11 weeks of age over seven generations. Selection was practised for high level in two replicate lines and for low level in two replicate lines, and there was an unselected control. There was a response in both directions, and the divergence of 12·4 ng/ml observed in generation seven was equivalent to about 20% of the base population mean or nearly one phenotypic standard deviation. The realised heritability was 9%.Plasma thyroxine level had a repeatability of 0·54 when two measurements were made 24 h apart. The responses made at 11 weeks in males were also evident in both males and females at 5 weeks. Plasma tri-iodo thyronine (T3) concentrations showed a correlated response almost as large, relative to the mean level, as that in T4.Positive correlated responses were observed in total weights of the litter at 12 days, and in individual weights at 3, 6 and 9 weeks, the responses in the early weights being greater relative to their mean. The results suggest that the correlated weight changes were due to genetic responses in maternal characteristics, probably milk production, rather than individual growth.
A Method for the Selection of Deletion Mutations in the L-Proline Catabolism Gene Cluster ofAspergillus nidulans
Authors: Arst Herbert N. , Jones Susan A. , Bailey Christopher R. 
Published: September 2009

SUMMARYInterest in the selection of mutations affecting L-proline catabolism inAspergillus nidulansis heightened by the involvement of one of the very few examples of a cluster of functionally related genes in an eukaryote and by an increasing awareness of the biological phenomena in which proline and proline catabolism participate. ThesasA-60 (semialdehyde sensitive) mutation inA. nidulansresults in toxicity of catabolic precursors of L-glutamic γ-semialdehyde (or its internal Schiff base L-Δ1-pyrroline-5-carboxylate) and succinic semialdehyde, apparently without affecting the catabolic pathways concerned. AssasA-60 is unlinked to theprngene cluster, specifying the gene products necessary for L-proline catabolism and as L-proline, a precursor of L-glutamic γ-semialdehyde, is highly toxic tosasA-60 strains, this forms the basis of a powerful positive selection technique for obtaining a number of types ofprnmutations. Many of theseprnmutations can be directly classified according to the gene product(s) affected on the basis of growth phenotype with respect to L-arginine and L-ornithine utilization, proline-dependent resistance to certain toxic amino acid analogues and effect on supplementation of proline auxotrophies. The availability of both a positive selection technique and an extensive nutritional screening system has enabled the identification of fourteen spontaneous deletion mutations, recognized as extending into theprnB gene, specifying the principal L-proline permease, and into at least one otherprngene. These deletion mutations have been partially characterized both genetically and biochemically. In particular their use has greatly facilitated fine-structure mapping of theprncluster and aided studies of the regulation ofprngene expression.
Unstable drug resistance inStaphylococcus aureusM4
Authors: Grubb W. B. , Annear D. I. 
Published: September 2009

SUMMARYStaphylococcus aureusM4 has chromosomal resistance to streptomycin, plasmid-borne resistance to penicillin and tetracycline and probably chromosomal inducible erythromycin resistance. It also has constitutive erythromycin resistance which is unstable and linked to kanamycin and lincomycin resistance and the ability to produce a diffusible pigment. Variants have been isolated which have stable kanamycin, lincomycin and constitutive erythromycin resistance and these do not produce the diffusible pigment. In transduction experiments kanamycin, lincomycin and constitutive erythromycin resistance were always co-transduced together with streptomycin resistance. The transduction frequencies were approximately 100 times higher with the stable variants compared with the parent. The transductants, irrespective of the donor used, all had stable resistance and did not produce the diffusible pigment. Although transduction with UV-irradiated transducing lysates was characteristic of a plasmid, no corresponding plasmid DNA has been detected.
The satellite DNAs of Drosophila simulans
Authors: Lohe A. R. 
Published: September 2009

SUMMARYThe resolution of antibiotic-CsCl gradients enabled an examination of the satellite DNAs in the nuclear DNA of Drosophila simulans. Of the eight distinct satellite DNAs which were detected, four band at almost the same buoyant density in CsCl but can be resolved in netropsin sulphate-CsCl gradients. Each consists of a repeated sequence which, in five of the satellites, is shown to be arranged in tandem for long regions of the chromosomal DNA. One satellite (1·697 g/ml in CsCl) contains repeated sequences interspersed with other sequences. The satellite DNAs were compared with the satellite DNAs known to be present in the sibling species, D. melanogaster. The two species have different overall complements of satellite DNAs, but one satellite (1·672 g/ml) may be identical.
Chromosomal locations ofcatA, pobA, pcaA, dcuandchugenes inPseudomonas aeruginosa
Authors: Matsumoto Hideki , Nakazawa Teruko , Ohta Shin , Terawaki Yoshiro 
Published: September 2009

SUMMARYEleven catabolic markers have been located on the chromosome ofPseudomonas aeruginosaPAO using FPS-mediated conjugation and G101 transduction. Most of these markers are located in the region 20–35 min, and the remainder in the region later than 60 min. Fourchugenes concerned in the sequential degradation of choline to glycine are closely linked.
Further observations on intragenic recombination inDrosophila melanogaster
Authors: Hilliker Arthur J. , Chovnick Arthur 
Published: September 2009

SUMMARYThis report examines several issues bearing upon intragenic recombination in higher eukaryotes. The fine structure data accumulated in our analysis of the genetic organization of the rosy locus inDrosophila melanogaster. Firstly, we confirm that a conversion event has a markedly less than 50% probability of resulting in flanking marker exchange, a finding consistent with more recent analyses of the availableSaccharomycesdata (e.g. Fogelet al.1978). As reported earlier, co-conversion of recombinationally separable sites within therosylocus occurs (McCarron, Gelbart & Chovnick, 1974). In this report, we demonstrate that the frequency of co-conversion is inversely proportional to the distance between co-converting sites. As in fungi, real conversion frequency differences are observed amongrosymutant alleles, and the data suggest that there may be a relationship between allele conversion frequency and map position. UnlikeNeurosporaandSaccharomyces, only one flanking marker exchange class is recovered from any given mutant heteroallele recombination experiment. In this respect, theDrosophilasystem resemblesAspergillus. As inNeurosporaandSaccharomyces, rosylocus intragenic recombinants associated with flanking marker exchange exhibit interference with crossing over in adjacent regions, while no interference is seen among recombinants exhibiting parental flanking markers. Finally, experimental results are discussed which demonstrate the occurrence of postmeiotic segregation inDrosophila. These analogies betweenDrosophilaand fungi provide further evidence in support of the notion that eukaryotes share common molecular mechanism(s) of meiotic recombination.
The recovery and preliminary examination of a temperature sensitive suppressor of thecryptocephalmutant ofDrosophila melanogaster
Authors: Sparrow John C. 
Published: September 2009

SUMMARYThe recovery of two EMS induced mutations which are dominant suppressors of the lethality ofcryptocephalinDrosophila melanogasterare described. One of these mutationsSu(crc)1is described in detail. It maps very close tocryptocephalat 54·7 on the second chromosome and its suppression of cryptocephal is temperature-sensitive. Temperature shift experiments show that the temperature-sensitive period is from before the pupariation until 12 h post pupariation. The temperature-sensitive period ofSu(crc)1is discussed in relation to the expression ofl(2)crc, head eversion and the timing of pupal chitin synthesis.
Evidence for Two Regions in the MousetComplex Controlling Transmission Ratios
Authors: Styrna Józefa , Klein Jan 
Published: September 2009

SUMMARYFour newthaplotypes,tTu1throughtTu4, are described, three of them derived from thetw12tfhaplotype and one (tTu4) from thetw2haplotype. ThetTu1andtTu4haplotypes cause taillessness inT/tTu1orT/tTu4heterozygotes, lack the lethality factor, weakly suppress recombination in theT−H−2interval, and are transmitted to offspring fromtTu/+ males at nearly Mendelian ratios. ThetTu3haplotype resemblestTu1andtTu4except for the fact that theT/tTu3heterozygotes have normal-length tails. ThetTu2haplotype probably carries the lethal factor oftTu12tf, suppresses crossing-over in theT-H-2andtf-H-2intervals, and displays a slightly subnormal transmission ratio. In the compound heterozygotetTu1/tTu2, the male transmission ratio of thetTu1chromosome is close to that of the originaltTu12tfhaplotype. A similar effect is observed in thetTu3/tTu2heterozygote. This observation is interpreted as evidence for two regions within thetcomplex controlling the male transmission ratios. One of the regions is close to the tail-modifying region, the other is close to the lethality factor. Our findings parallel closely those made in the segregation distorter system inDrosophila.
Lens opacity: a new gene for congenital cataract on chromosome 10 of the mouse
Authors: Lyon Mary F. , Jarvis Susan E. , Sayers Irene , Holmes Roger S. 
Published: September 2009

Mouse mutant genes which result in defects similar to those of medical importance in man may be of value as models for the study of the defect concerned. We report here a new gene causing congenital cataract in the mouse, which may be useful in the understanding of cataract in man.A further point of interest is that Kratochvilova & Ehling (1979) have recently developed a new method of measuring increased mutation rates in the mouse, by examining offspring of animals treated with mutagens for the presence of cataracts due to mutant genes. For the purposes of this test it is valuable to have information on the number and map position of loci which can mutate to give cataracts.
Allelic variation at several different genetic loci determines the major urinary protein phenotype of inbred mouse strains
Authors: Hainey Sheila , Bishop J. O. 
Published: September 2009

SummaryWe have examined the major urinary protein (MUP) phenotype of three inbred mouse strains by one-dimensional isoelectric focusing in acrylamide gels. Each strain gave a distinct pattern of major and minor bands. In the three strains together, seven major and about seven minor bands were observed. F1 phenotypes were intermediate. F2 phenotypes can be explained by recombination between allelic variants at four or more different genetic loci. We propose that variation in MUP phenotype is due in fact, to allelic variation at approximately seven structural gene loci, some of which are linked on chromosome 4. The remainder may or may not be linked to these.
Linkage disequilibrium, genetic distance and evolutionary distance under a general model of linked genes or a part of the genome
Authors: Takahata Naoyuki 
Published: September 2009

SummaryA general model of linked genes or a part of a genome is proposed which enables us to study various problems in molecular population genetics in a unified way. Several formulae with special reference to the linkage disequilibrium and genetic distance are derived for neutral mutations in finite populations, based on the method of diffusion equations. It is argued that the model and formulae are useful particularly when observations are made in terms of DNA sequence.
Genetic analysis of thetw73haplotype of the mouse using deletion mutations: evidence for a parasitic lethal mutation
Authors: Babiarz Bruce , Garrisi G. John , Bennett Dorothea 
Published: September 2009

SummaryMatings between mice bearing the dominant deletionThpand mice segregating for thetw73haplotype failed to produce the expected viable tailless (Thp/tw73) progeny. Histological analysis of litters fromThp/ + × + /tw73matings revealed an abnormal class of embryos which failed to implant normally between days 6·5 and 7·5 of gestation, and were indistinguishable fromtw73/tw73homozygotes.Thphomozygotes displayed a different lethal phenotype, failing to successfully make the transition from morula to blastocyst at day 3·5. These studies indicate that the mutation responsible for thetw73implantation defect maps within theThpdeletion. Sincetw73is viable with another deletion,Torl, thetw73defect must occur in the region of non-overlap betweenThpandTOrl. The possibility that thetw73-associated implantation defect is a parasitic lethal mutation (p), mapping to the proximal part of thetw73chromosome, is discussed.
The relationship between heterochromatic homology and meiotic segregation of compound second autosomes during spermatogenesis inDrosophila melanogaster
Authors: Hilliker Arthur J. , Holm David G. , Appels R. 
Published: September 2009

SummaryIn this report we examine the meiotic segregation of compound second autosomes sharing varying extents of heterochromatic and euchromatic homology. The second chromosome heterochromatin does not appear to influence the random meiotic segregation of compound second autosomes during spermatogenesis; however, the proximal euchromatin is implicated in male meiotic pairing. We conclude that male autosomal meiotic pairing sites are specific euchromatic chromosomal regions.
Mutants affecting amino acid cross-pathway control inNeurospora crassa
Authors: Barthelmess Ilse B. 
Published: September 2009

SummaryArginine-requiring mutants ofNeurospora crassawere isolated using a strain partially impaired in an enzyme of the arginine pathway (bradytroph). Among these, five strains were found which carry mutations at a new locus,cpc-1+. The recessivecpc-1alleles interfere with the cross-pathway control of amino acid biosynthetic enzymes. The enzymes studied, three of arginine and one each of histidine and lysine biosynthesis, fail to derepress under conditions which normally result in elevation of enzyme concentration, namely arginine, histidine or tryptophan limitation. Enzymes not involved in amino acid biosynthesis are still able to derepress in the presence ofcpc-1. In wild-type backgound, i.e. with the bradytroph replaced,cpc-1strains lose the original arginine-requirement.cpc-1mutations confer sensitivity of growth to 3-amino-1,2,4-triazole.
The extent to which gene conversion can change allele frequencies in populations
Authors: Lamb B. C. , Helmi S. 
Published: September 2009

SummaryThe gene conversion parameters which affect allele frequencies in populations are defined, and their ranges and typical values are given for several genera of fungi, where meiotic octads and tetrads provide the best information on conversion. Both gene conversion and disparity in direction of conversion are common. Data fromAscobolus immersusshow that conversion properties are largely stable with time, but can be changed environmentally and by genetic conversion control factors. Equations are given for the interactions of selection, mutation and gene conversion in determining equilibrium frequencies. Numerical examples, using typical values of conversion parameters from the fungal data, show that for alleles which are selectively neutral or have very low selection coefficients, conversion will often have very large effects on their equilibrium frequencies and may lead to fixation. Where selection coefficients are higher, conversion has major effects on the frequencies of deleterious recessive alleles, but lesser effects on deleterious dominant alleles: a critical comparison is that ofswith 2y. The available estimates for conversion parameters (at least in fungi) are of a magnitude to make gene conversion an important factor in evolution.
A computer model of speciation by founder effects
Authors: Charlesworth B. , Smith D. B. 
Published: September 2009

SummaryA computer model of a two-locus genetic system with epistatic selection was used to investigate factors influencing the probability of the origin of reproductive isolation, due to a genetic revolution following a founder event (Mayr, 1954; Carson, 1975). Restricted population size can sometimes cause such a system to drift from one equilibrium to another, which can result in loss of fitness to hybrids with the ancestral population. The chance of such an event was found to be low unless the bottleneck in population size associated with the founder event was preceded by many generations of relaxed selection. It is highest when the bottleneck is not prolonged and when the population size during the bottleneck is not too small. It seems to be difficult to achieve a high degree of reproductive isolation in one step by this method, and it is concluded that it is unlikely to be a major cause of rapid speciation, although it could be a contributory factor.
Non-random X-chromosome inactivation in the mouse: difference of reaction to imprinting
Authors: Falconer D. S. , Isaacson J. H. , Gauld I. K. 
Published: September 2009

SummarySelection for increased and for decreased expression of the sex-linked gene brindled (Mobr) in heterozygous females produced two lines with non-randomXchromosome inactivation. In the High line theXchromosome marked by brindled was active in about 60% of cells, while in the Low line it was active in about 25% of cells. The whole of the difference was caused by the chromosomes carrying brindled: neither the unmarkedXchromosome nor the autosomes were differentiated. There was a positive correlation between the expression of brindled in daughters and mothers. This was probably not caused by residual genetic variation, but was more probably a maternal effect similar to that described by Cattanach & Papworth (1981). On this assumption the daughters' scores were adjusted to a standard maternal score. Enzyme assays on females doubly heterozygous for brindled and for the sex-linkedPgk-1locus proved that the percentage of brindled in the coat provided an accurate measure of theX-inactivation proportions in the blood, liver and kidney. The accuracy was improved by adjustment for maternal score. In the selection lines, brindled was always inherited from the mother. When brindled was transmitted by male parents the probability of activation of its chromosome was increased by 8 percentage points in the High line and 18 in the Low line. This effect of the parental source is much greater than has previously been reported. The responses to selection can be interpreted in terms of theXcelocus controlling the activation probability, different alleles on the chromosomes carrying brindled being selected in the two lines. If this interpretation is correct, the alleles on one or both of the chromosomes carrying brindled were different from any of the three known alleles. The different effects of male transmission in the two lines can be described as a difference between the two chromosomes in their reactions to imprinting. This difference might possibly also be due to theXcelocus.
Genetic basis of susceptibility to splenic lipofuscinosis in mice
Authors: Crichton D. N. , Shire J. G. M. 
Published: September 2009

SummarySpleens with black pigment in them were found in 4–57% of mice from 17 stocks, all sublines of C57BL or with significant C57BL ancestry. Splenic lipofuscinosis was absent from 16 stocks, including three C57BL/6By × BALB/cBy recombinant - inbred lines. Progeny testing showed all C57BL/6J mice to be equally likely to develop black spleens. The penetrance of lipofuscinosis differed between sublines but not between the sexes or between laboratories. Susceptibility to lipofuscinosis showed dominant, autosomal, inheritance in F1 hybrids. Observations on backcrosses and on recombinant inbred lines and their intercrosses indicated the existence of two genetic factors. Splenic lipofuscinosis was prevented either by a deficiency of melanin or by homozygosity for a non-C57BL allele close to thec-pregion of chromosome 7. The presence of a C57BL allele at a locus on another chromosome is necessary for lipofuscinosis to occur.
Theoretical study on the accumulation of selfish DNA
Authors: Ohta Tomoko 
Published: September 2009

SUMMARYThe accumulation of selfish DNA in eukaryotic genomes was studied from the standpoint of population genetics. Selfish DNA is assumed to replicate itself within a haploid set. For the selectively neutral case, the fate of a single self-replicating DNA segment (unit) within a population was investigated by the method of the probability generating function, and by Monte Carlo simulation, with special reference to the probability of survival and average number of units per haploid set. For the selectively deleterious case at the organismal level, the equilibrium between new occurrence and selective elimination was studied, and the average and variance of the number of units per haploid set in the population was examined by Monte Carlo simulation. It is shown that the process of self-replication (duplication–deletion) plays an essential role for the maintenance and elimination of selfish DNA.