bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromosomal basis of dosage compensation in Drosophila: II. The DNA replication patterns of the male X-chromosome in an autosome—X insertion in D. melanogaster
Authors: Lakhotia S. C. 
Published: September 2009

SUMMARYThe functional morphology and the replication pattern of the male X-chromosome in an autosome-X insertion stock (T(1;3) 05) of Drosophila melanogaster have been examined. In larval salivary glands carrying this insertion neither the enlargement and pale staining of the single male X, nor the characteristic early completion of replication cycle, as revealed by 3H-TdR autoradiography is in any way changed. The normal properties of the inserted autosomal segment are also unaltered. The results appear to support a ‘piecemeal’ type of dosage compensation mechanism in Drosophila operating through the male.
A chromosomal factor exerting a predetermining effect on morphogenesis in the multicellular green alga Ulva mutabilis
Authors: Fjeld Asbjørn 
Published: September 2009

SUMMARYA new spontaneous mutant bubble (bu) with a marked effect on early morphogenesis in the multicellular green alga, Ulva mutabilis is described. It behaves as a recessive chromosomal mutant. The bu+ gene product formed in heterozygous sporophytes exerts a predetermining effect on morphogenesis of haploid gametophytes with the bu genotype. It is suggested that the product of the bu+ gene affects the orientation of the mitotic spindles during early development.
Genetic analysis of an unequal chromosomal translocation inAspergillus nidulans
Authors: Bainbridge B. W. 
Published: September 2009

SUMMARYTranslocation T(III–VIII) inAspergillus nidulanshas been analysed by the detection of meiotic linkage between markers previously located separately on linkage groups III and VIII. The breakage points have been mapped by the detection of linkage between the crinkled type and genetic markers in the region of the break. A segment from linkage group III, approximately 43 units long and including the markersmoC96, sC12, sA1andcnxH3, has been translocated into linkage group VIII. The breakage point is betweensu6proAandmoC96and the attachment point is close tochain linkage group VIII. It seems probable that the segment has been inserted into linkage group VIII.
Acridine treatment of F+and Hfr strains ofEscherichia coli K12carrying a neomycin-kanamycin resistance determinant
Authors: Grindley June N. , Grindley N. D. F. , Anderson E. S. 
Published: September 2009

SUMMARYThe F factor and the K resistance determinant form an R factor (KF) inE. coliK12. In this R factor the two plasmids are independent of each other and occupy different attachment sites in the host cell.Treatment of an F+(K) strain with acriflavine and acridine orange yielded the following classes: F+K−; F−K+; and F−K−. The K determinant was thus curable independently of F, which supports the hypothesis of independence of the two plasmids. In Hfr(K) strains, K remains curable with acridines while F is immune. Thus, K remains independent of F in both the F+and Hfr states.The use of higher concentrations of acridine orange than those needed for cure of K in the F+(K) strain resulted in no elimination of K, although the F factor was absent from all surviving lines tested. It is suggested that this is caused by equal inhibition of replication of both the chromosome and K, and greater inhibition of that of F.
Transformation ofSarcina flavaandMicrococcus flavocyaneus
Authors: Kane Caroline M. , Kloos W. E. 
Published: September 2009

SUMMARYSarcina flavaATCC 540 (ade) andMicrococcus flavocyaneusATCC 8673 (ade), two related micrococci, were transformed to prototrophy at frequencies as high as 0·02% and 0·005% of colony-forming units, respectively. Both of these organisms were transformed by selected prototrophic strains ofMicrococcus lysodeikticus, M. flavocyaneus, S. flavaandSarcina lutea.
Studies on genetic organization in higher organisms: III. Confirmation of the single cistron-allele complementation model of organization of themaroon-likeregion ofDrosophila melanogaster
Authors: Finnerty Victoria , Chovnick Arthur 
Published: September 2009

SUMMARYA genetic fine-structure experiment onDrosophila melanogasteris described, which makes use of a lethal selective system which permits survival only of recombinants in thema-lregion, including exchanges between site mutants ofma-l. On the basis of prior mapping information, the experiment was designed to select forma-ldouble mutant recombinants. Utilizing a pair of complementingma-lmutants, double mutant meiotic products were recovered whose complementation properties provide independent support for the single-cistron, allele complementation model of organization of the maroon-like region inferred from other experiments described earlier.
Somatic segregation of the killer (k) and neutral (n) cytoplasmic genetic determinants in yeast
Authors: Bevan E. A. , Somers J. M. 
Published: September 2009

When killer and neutral strains of Saccharomyces cerevisiae are crossed the resulting diploid clones possess a killer phenotype and when spored yield a complete range of tetrad ratios.The combined results of analysing tetrads and vegetative cells of diploid clones derived from two different neutral × killer crosses (K1 × N1 and K2 × N1) demonstrate that the range of tetrad ratios can be accounted for by the occurrence of somatic segregation of killer (k) cytoplasmic determinants prior to sporulation. Such results support the genetic model for the inheritance of the killer character in yeast already proposed (Somers & Bevan, 1969).During the course of these studies a correlation was found between the strengths of the killer phenotypes of diploid colonies and the proportions of killer spore cultures obtained after sporulation of their cells.
Mitotic non-conformity inAspergillus nidulans: the production of hypodiploid and hypohaploid nuclei
Authors: Roper J. A. , Nga B. H. 
Published: September 2009

Strains ofAspergillus nidulanswith a chromosome segment additional to the normal complement are vegetatively unstable. Previous work suggested that the deletions occurring at mitosis were confined to the unbalanced segments. It has been shown now that deletions, while probably always involving a duplicate segment, may extend beyond it to produce hypohaploids and hypodiploids, respectively, from unbalanced haploid and unbalanced diploid parents.Hypoploids have been proposed tentatively as an explanation for some cases of phenotypic variegation; on this basis it is possible to account for some of the diverse phenomena shown by, for example, position-effect variegation.
The study of multiallelic genetic systems by matrix methods
Authors: Cannings C. 
Published: September 2009

A matrix notation is developed to facilitate study of natural selection in large populations. The processes of mating (taking into account differences between genotypes in fertility in both sexes), segregation, and differential viabilities are each expressed in matrix notation. Assortative mating and non-random segregation can also be described by the method. The separate processes can then be combined to give simple equations relating the genic and genotypic frequencies in one generation to those in the previous generation. This will facilitate computer treatment of natural selection processes.The method can also be used to study equilibria and the conditions of their stability by examining the latents roots of the matrix. Several special cases of selection at an autosomal locus are examined. The method can be extended to sex-linked loci and two special cases are discussed.
The effect of suppressing crossing-over on the response to selection inDrosophila melanogaster
Authors: McPhee C. P. , Robertson Alan 
Published: September 2009

SUMMARYA selection experiment for sternopleural bristles inDrosophila melanogasterwas undertaken to measure the effect of suppressing crossing-over on chromosomes II and III using the inversions Curly and Moiré marked with a dominant gene, which severely reduce crossing-over. In one set of lines selected wild-type males were mated to selected females, heterozygous forCyandMé, and in a parallel set selected males carrying the inversions were mated to selected wild-type females. Because there is no crossing-over in the males in this species, crossing-over is much reduced in the first set and is at its usual level in the second. The effect of the selection was measured on flies which did not carry the inversions. The suppression of crossing-over reduced the advance at the limit by 28 ± 8% for selection upwards and by 22 ± 7% for selection downwards. The segregation ratios of the inversions were observed throughout the experiment. At the end, the proportion of wild-type flies emerging was not different in the two sets of lines. The results are consistent with an assumption of initial linkage equilibrium between loci affecting sternopleural bristles in the base population.
A genetic analysis of non-disjunction and mitotic recombination inNeurospora crassa
Authors: Threlkeld S. F. H. , Stoltz J. M. 
Published: September 2009

SUMMARYThe frequency of the more common patterns of non-disjunction in Neurospora was studied. Detection of these asci was accomplished by the use of pantothenate requiring strains grown on reduced amounts of pantothenate, so that combinations of dark, pale, and aborted spores provided evidence of non-disjunction. The isolates from five non-disjunction asci were examined in detail and an apparently high frequency of mitotic recombination was detected for presumed disomic isolates. An hypothesis concerning a mechanism of non-disjunction is presented.
The control of plastid inheritance in Pelargonium
Authors: Tilney-Bassett R. A. E. 
Published: September 2009

SUMMARYTwenty-four reciprocal crosses between two green and six chimera cultivars, containing respectively normal green and mutant white plastids in their germ layers, were analysed for their segregation patterns of green, variegated and white embryos, and for their fertility data.Analysis of variance of fertility data showed that W × G crosses were generally less fertile than the reciprocal G × W crosses, but this was not correlated with selection against any particular class of embryo.Analysis of segregation patterns showed that they were essentially the same with a constant female and varying male parent, but change the female and the pattern could be radically altered. The six different mutant females with both constant green males could be arranged in a sequence in which white plastids were increasingly successful, and white and variegated embryos increasingly frequent. A similar sequence was demonstrated with three green females and two constant white males. It was concluded that the major control of plastid inheritance was determined by the female nuclear and plastid genotypes, with the male having only a minor, modifying influence even when male plastids were more successfully transmitted than female ones.The very low frequencies of variegated embryos in some crosses led to a rejection of the classical hypothesis of sorting-out from mixed cells, and its replacement by the hypothesis that pure green or pure white embryos arise by the replication of only one plastid at a time, whereas variegated embryos arise by replication of both plastids.
Genetics of a chain-forming mutant ofEscherichia coli: Transduction and dominance of theenvAgene mediating increased penetration to some antibacterial agents
Authors: Normark Staffan 
Published: September 2009

SUMMARYWe have recently described a chain-forming mutant ofEscherichia coliwhich showed a decreased resistance to ampicillin and several other antibiotics (Normark, Boman & Mattson, 1969). The gene mediating drug sensitivity was denotedenvAand by conjugation mapped at 2–4 min. Transduction experiments have now shown thatenvAis located betweenleuandaziat 1·5 min. The mapping was facilitated by the finding thatenvAmediated sensitivity to actinomycin D, rifampicin and gentian violet. TheenvAlocus could be genetically differentiated from thepealocus mediating resistance to phenethyl alcohol (Yura & Wada, 1968). Studies using partial diploids revealed thatenvAwas recessive to its wild-type allele both when located on an episome and on the chromosome.Assuming that revertants fromenvAto the wild-type allele could be selected as ampicillin-resistant derivatives, such mutants were isolated and their phenotype characterized. Reversion to ampicillin resistance was accompanied by reversion to insensitivity to actinomycin D. However, not all revertants exhibited wild-type tolerance to rifampicin. Three different ampicillin-resistant revertants were studied genetically. The results indicate that these strains contain suppressor mutations in theenvAregion of the chromosome. It is suggested that theenvAgene, directly or indirectly, affects the EDTA sensitive ‘permeability barrier’ of the surface layer ofEscherichia coli.
Penicillinase synthesis inStaphylococcus aureus: the effect of inducer and of the cellular location of the genetic determinants on the amount of enzyme formed
Authors: Asheshov Elizabeth H. , Woods Jennifer M. , Dyke K. G. H. 
Published: September 2009

SUMMARYA comparison was made of the amount of penicillinase produced by strains ofStaphylococcus aureuscarrying chromosomal penicillinase genes, plasmid penicillinase genes and strains carrying both chromosomal and plasmid genes. Plasmid genes were found to produce at least twice as much enzyme as homologous chromosomal genes. The results suggest that there are, on average, two plasmids per chromosome in exponentially growing cells.Two inducers were used in these experiments—methicillin and 2-(2′-carboxyphenyl)-benzoyl-6-aminopenicillanicacid (CBAP). The latter proved a more efficient inducer than methicillin and this difference was most apparent when more than onei+gene was present, which suggests that the efficiency of induction reflects the ability of the inducer to react with represser.
Mutant Hfr strains defective in transfer: restoration by F-like and I-like de-repressed R factors
Authors: Cooke Marylyn , Meynell Elinor , Lawn A. M. 
Published: September 2009

SUMMARYMutants of Hfr strains ofEscherichia coliK12 defective in conjugation owing to failure to produce sex pili were isolated by resistance to F-specific phage. Tests of the ability of six de-repressed F-like R factors and four de-repressed I-like R factors to restore Hfr donor behaviour to these mutants indicated that there were several ways in which such restoration could occur. Of a total of 26 defective mutants, 12 were restored by F-like R factors. In these twelve, the function of the integrated F factor was evidently restored, because the sex pili contained F pilin subunits, distinguishable from the R pilin by serological tests. In contrast, among the four I-like R factors, only two were effective, butin all 26 defective mutants; the restored Hfr bacteria produced only I-like pili. The I-like sex factors, in restoring Hfr donor behaviour, did not therefore act by complementing the defective F.
Mitotic mapping ofSchizosaccharomyces pombe
Authors: da Cunha Miguel Flores 
Published: September 2009

SUMMARYGenetic mapping by means of mitotic haploidization (induced by parafluoropkenylalanine) and mitotic crossing-over was carried out with the fission yeastSchizosaccharomyces pombe. Thirty-two different genetic markers were involved in this investigation; some meiotic linkage relationships had been previously reported (Leupold, Megnet) for 16 of these loci. Mitotic haploidization experiments resulted in the genetic identification of six chromosomes in the haploid complement.Furthermore, in an attempt to study the mechanism of action of parafluorophenylalanine (pFPA) on mitotic haploidization, pedigree analyses were performed by micromanipulation of diploid cells growing in the presence of pFPA. Haploid cells were detected after 40 hours of contact with the analogue and many lethal pedigree branches were observed. These observations seem to agree with Käfer's (1961) and Lhoa's (1968) suggestion that mitotic haploidization in Fungi is achieved by progressive loss of chromosomes throughout cell divisions.
The inhibitory action of transfer factors on lysis ofEscherichia coliK 12 by phages μ 2 and Φ 2
Authors: Pitton J. S. , Anderson E. S. 
Published: September 2009

SUMMARYA selection offi+resistance factors and transfer factors, when introduced into K 12F+, showed a range of inhibitory activity of lysis by the male-specific phage μ 2. This range can be used to subdivide thefi+factors intofi+1,fi+2,fi+3andfi+4classes, according to the degree of inhibition of μ 2 lysis. To this subdivision can be added restriction of the ‘female-specific’ phage φ 2.Introduction of all thefi+factors tested into K 12 HfrH totally inhibited lysis by μ 2 in spot tests, but with twofi+1and onefi+2factors visible lysis was obtained in agar-layer tests. These three factors caused least inhibition of transfer ofproby HfrH. It can be assumed that both tests reflect lower inhibition of sex fimbrial formation by thesefi+factors than by the remainder.Thefi−factors, when introduced into K 12, can be subdivided on the basis of restrictive effects on phage φ 2.These effects can be added to phage restriction in the salmonellae for the purposes of further classification of the transfer factors and R-factors.
Genetic studies of thebincompatability locus ofUstilago maydis
Authors: Puhalla John E. 
Published: September 2009

SUMMARYTheblocus ofUstilago maydisis both an incompatibility locus and a pathogenicity locus. There are several differentbfactors, and they are randomly distributed and equally frequent in the natural population. A sample of 62 lines contained 18bgroups and permitted an estimate of no more than 25bgroups in the natural population. All lines within the samebgroup are indistinguishable in their mating behaviour. No linkage was detected betweenband any of the four biochemical markers tested. No intrafactor recombinants atbwere found among more than 6700 progeny. Differences in degree of pathogenicity between solopathogenic diploids and comparable haploid by haploid crosses were detected.
OnXinactivation inXOembryos of mammals
Authors: Chandra H. Sharat 
Published: September 2009

SUMMARYBy analogy with the situation in coccids it is suggested that in mammalianXOembryos the singleXturns heterochromatic in some cells, but that such a change does not result in cell death because theXthen reverts back to an euchromatic and active state. This testable alternative to the Gartler–Sparkes hypothesis would imply that the anomalies of theXOTurner syndrome are largely due to imbalance of sex-linked genes rather than developmental damage resulting from cell death and that mammalianXinactivation might become reversed in response to special developmental needs.
The founder effect and response to artificial selection
Authors: James J. W. 
Published: September 2009

SUMMARYThe response to selection in any line depends on the size of the initial sample by which the line is founded. For a single locus with additive gene action the effects of number of founders on early rate of response and on final limits are studied in relation to selection intensity and number of parents in the selected line. The reduction in total response caused by a small number of founders is greatest for large populations under intense selection, especially when the desirable alleles are rare in the base population. If these alleles are at high frequencies it is possible that a line which has gone through a bottleneck may be more sensitive to a reduced population size during subsequent selection than a line which has not. Under some conditions replicate selection lines founded with small samples are likely to be less variable in response than lines founded with moderately large samples.
Genetic aspects of fertility and endocrine organ size in rats
Authors: Mullen R. J. , Hoornbeek F. K. 
Published: September 2009

SUMMARYAn investigation of the genetic aspects of fertility was conducted among inbred and hybrid generations of rats. The high-fertility LEW strain and the low fertility CAS strain were crossed and their hybrids inbred for four generations. Litter size, ovulation rate, sterility, and the weights of the thyroid, pituitary, adrenals, testes, seminal vesicles, ventral prostate, uterus, and ovaries were analysed in inbred and hybrid rats for evidence of strain differences and heterosis and in successive generations of sib matings for inbreeding depression.CAS females produced smaller litters and had smaller thyroids, pituitaries, adrenals, ovaries, and uteri than LEW females. CAS males had larger testes but smaller adrenals than LEW males. Results of crosses included heterosis for female pituitary and ovary weights, but inbreeding depression for the weights of male adrenals, seminal vesicles, and ventral prostates, and female thyroids and uteri. Ovulation rate did not differ between strains and was not an important determinant of litter size in this study.The decrease in litter size as a result of inbreeding was due partly to the inbreeding of the parents and partly to the inbreeding of the litter.
Controlling elements in the mouseX-chromosome III. Influence upon both parts of anXdivided by rearrangement
Authors: Cattanach B. M. 
Published: September 2009

SUMMARYData are presented which support the conclusion that in thefleckedtranslocation,T (1; X) Ct, there is a spread of inactivation into both sides of the autosomal region inserted into theX. This would indicate that both parts of the dividedXare subject to theX-inactivation process. The data also demonstrate that the inactivation of autosomal genes lying near each end of the insertion are modified by theX-chromosome controlling element system,Xce. Since the element modifies the heterozygous expression ofX-linked genes on one side of the insertion, it would therefore be expected that it similarly modifies the heterozygous phenotypes of those on the other side. The data thus support the concept that the controlling element is the master gene, receptor site or inactivation centre which regulates theXinactivation process.
Substitution of rye chromosome 5R for its three wheat homoeologues
Authors: Bielig L. M. , Driscoll C. J. 
Published: September 2009

SUMMARYChromosome 5R ofSecale cerealevar. Imperial has been substituted for chromosomes 5A, 5B and 5D of hexaploid wheat. There is evidence of compensation, in terms of vigour, in all substitution lines. Chromosome 5R rectifies the male sterility of nullisomics 5A and 5D; however, it is unable to circumvent the meiotic irregularity and male sterility of 5B-deficient stocks. Another instance of wheat-rye chromosome pairing, in the absence of chromosome 5B, is reported. The data reported here demonstrate that the long arm of 5R is the more essential arm and indicate that chromosome 5R is homoeologously related to the group 5 chromosomes of wheat.
Induced variation in chiasma frequency in Rye in response to phosphate treatments
Authors: Bennett M. D. , Rees H. 
Published: September 2009

SUMMARYPlants of two rye genotypes, one highly inbred, the other not, were grown with varying amounts of available mineral phosphate. In two experiments, one using culture solutions, the other a field experiment, the results show an effect of phosphate treatments on mean chiasma frequency at first metaphase in meiocytes. Plants given increased amounts of phosphate showed an increase in chiasma frequency. A similar effect of phosphate on chromosome size and mass at mitotic metaphase in meristems is known and there may be a direct link between chromosome size and chiasma frequency.