bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitotic mutants ofAspergillus nidulans
Authors: Morris N. Ronald 
Published: September 2009

SUMMARYForty-five temperature-sensitive mutants ofAspergillus nidulanswhich are defective in nuclear division, septation or distribution of nuclei along the mycelium have been isolated, and most have been subjected to complementation analysis and mapped to chromosome. Thirty-five of the mutants were unable to complete nuclear division at the restrictive temperature. Twenty-six of these mutants exhibited a co-ordinate drop in both spindle and chromosome mitotic indices at 42 °C, indicating that they fail to enter mitosis. These mutants have been assigned to the gene symbolnim. Nine mutants exhibited a co-ordinate rise in spindle and chromosome mitotic indices at 42 °C, indicating that they are arrested in mitosis. These mutants were assigned the gene symbolbim. Five mutants failed to form septa and were given the gene symbolsep; and five mutants had an abnormal nuclear distribution and were given the gene symbolnud. All of the mutations were recessive. Most of the mutants were in different complementation groups. Mutants in the same complementation groups were phenotypically similar, but phenotypically similar mutants were not necessarily or usually in the same complementation group. There was no evidence for genetic clustering of phenotypically similar mutants. The mutants were located on all eight chromosomes.
Tandem duplications inDrosophila melanogaster: III. Intrachromosomal exchange of a heterozygous tandem duplication
Authors: Kalisch Wolf-Ekkehard 
Published: September 2009

SUMMARYDuring meiosis the two parts of a tandem duplication are able to pair in a double loop instead of pairing with the corresponding region of the homologous chromosome. The frequency of intrachromosomal exchange within this double loop was measured in heterozygous females of tandem duplicationDp(1; 1)Grby the phenotypes of the exceptional F1males. The intrachromosomal exchange frequency is increased significantly by both the ‘interchromosomal effect’ of heterozygous inversions in the autosomes and by a double inversion in the homologousXchromosome. Distribution of the exchange events depends on the pairing situation and its frequency within the double loop. The analysis of clusters of intrachromosomal recombinants observed favours the assumption that this exchange type is exclusively a meiotic event.
A genetic method for measuring non-disjunction in mice with Robertsonian translocations
Authors: Lyon Mary F. , Ward Hazel C. , Simpson Gillian M. 
Published: September 2009

SUMMARYA high frequency of chromosomal non-disjunction occurs spontaneously in mice heterozygous for some Robertsonian translocations. If animals heterozygous for the translocation and homozygous for different alleles of a marker gene are mated together a few young homozygous for the marker arise through non-disjunction, and their frequency can be used as a measure. This method has been used with the Robertsonian translocation Rb(9.19)163H and the marker ruby ru (chr. 19); Rb(4.6)-2Bnr with brown (b) and misty (m) (chr. 4); and Rb(9.14)6Bnr with hairless (hr) and piebald (s) (chr. 14) respectively. The frequencies of marked young were: Rb163 0/5260 ruru; Rb2 21/1997 mm bb; and Rb6 19/1702 hrhr ss, and the corresponding calculated non-disjunction frequencies in each arm of the translocation were Rb163, <5 %; Rb2, 15%; Rb6, 15%. These figures show reasonably good agreement with values obtained by other methods. A search for genetic or environmental factors affecting the frequency of marked young in Rb2 and Rb6 revealed that in Rb2 the frequency increased with maternal age, whereas in Rb6 the maternal age of the marked young was non-significantly below that of the total progeny. The reasons for this discrepancy are not clear.
A recombination test to classify mutants ofBacillus subtilisof identical phenotype
Authors: Galizzi A. , Siccardi A. G. , Mazza G. , Canosi U. , Polsinelli M. 
Published: September 2009

SUMMARYWe have developed a recombination test inBacillus subtilisthat provides a tool for rapid genetic classification of mutants of identical phenotype. The test has been used to classify 25 ts mutants in nine recombination classes that have been proved by independent evidence to correspond to nine genetic loci.
The genetic control of protoperithecial production inSordaria brevicollis
Authors: Bond D. J. , MacDonald D. J. 
Published: September 2009

SUMMARYMutations have been detected which affect the production of protoperithecia inSordaria brevicollis. These mutations have been calledperithecial-1andperithecial-2. Ascus analysis revealed that the former was a centromere unlinked gene, whilst the latter was very close to the mating-type locus. Theper 1−per 2− genotype was female sterile. Recovery of fertility by a sterile culture occurred and perithecial analysis revealed that this recovery was due to the accumulation of revertantper 1+nuclei in the mycelium.Per l−per 2+colonies were fertile and gave a cross of characteristic appearance.
Equivalence of the A genome of bread wheat and that ofTriticum urartu
Authors: Chapman Victor , Miller T. E. , Riley Ralph 
Published: September 2009

SUMMARYLines ofTriticum aestivumChinese Spring (2n= 6x= 42) which were ditelocentric or doubly ditelocentric, in turn, for the 14 chromosomes of the A and B genomes were pollinated byTriticum urartu(2n= 14). The behaviour of the marked telocentric chromosomes was scored in the 14 distinct hybrids obtained from these pollinations. In 6 of the hybrids in which different A genome chromosomes were marked by telocentrics there were from 50 to 80% of the pollen mother cells in which the telocentrics were paired. In the seven hybrids in which different B genome chromosomes were marked the telocentrics were never paired. It was concluded that the genome ofT. urartumatched very closely the A genome of hexaploid wheat and that it did not correspond, as had been proposed by Johnson, to the B genome. The pairing behaviour of the 14T. aestivum×T. urartuhybrids was compared with earlier results obtained from hybrids betweenT. aestivumandT. boeoticum. It was proposed that the higher trivalent frequencies seen in theT. boeoticumhybrids could be due to homoeologous pairing and that the genotype ofT. boeoticumhas the capacity partly to suppress the activity of thePhlocus of chromosome 5B of wheat, as a result of which homoeologous pairing is normally prevented.
Mitochondrial factors in the utilization of sugars inSaccharomyces cerevisiae
Authors: Evans I. H. , Wilkie D. 
Published: September 2009

SUMMARYCytoplasmic petite mutants, spontaneous and induced, show various patterns of ability υ. inability to utilize the sugars galactose, α-methylglucoside and maltose, depending on the strain from which they were isolated. Petites recombine and segregate their different sugar deficiencies among vegetative diploid progeny when crossed, indicating mitochondrial control. Crosses between petites and wild-type further indicate that mitochondrial factors may be interacting with nuclear factors in a complex regulatory system.
Oral morphogenesis during asexual reproduction in Paramecium tetraurelia
Authors: Jones Warren R. 
Published: September 2009

SUMMARYOral morphogenesis in stock 51 of Paramecium tetraurelia was investigated using the techniques of Chatton-Lwoff and protargol silver impregnation. During the stomatogenesis accompanying divisional morphogenesis a new oral anlage field and endoral kinety are formed and persist throughout the interfission period in both the proter and the opisthe. This previously overlooked fact is important for understanding the developmental origins and significance of the endoral kinety and the oral anlage field. Previously, the kinetosomes constituting the oral anlage field were thought to be formed just prior to the onset of stomatogenesis, being in some way derived from the kinetosomes of the endoral kinety. The demonstration of a permanent anlage field as an integral component of the oral assemblage suggests that the earliest stages of stomatogenesis might best be viewed as temporally controlled surfacing and/or ciliation of pre-existing kinetosomes rather than their de novo synthesis. The endoral kinety would thus have no contributory role in the formation of the anlage field used in the immediately ensuing stomatogenesis.
Are macronuclear subunits inParameciumfunctionally diploid?
Authors: Nyberg Dennis 
Published: September 2009

SUMMARYThe organization of the genetic material in the macronucleus of ciliates has been the subject of considerable controversy. Two of the four models of macronuclear structure predict assortment of the alternative phenotypes of heterozygotes during vegetative growth. Early studies of the phenotypic behaviour of heterozygotes after macronuclear regeneration (Sonneborn, 1947) had supported a diploid subunit model. The availability of quantitative predictions of the rate of assortment for the haploid and chromosomal models (Preer, this volume) and the existence of two alleles controlling a quantitative trait, copper tolerance, inParamecium tetraurelia, has provided an opportunity to test these models. The median tolerance limits to copper of unselected sublines were measured as a function of age. There was no increase in the variance among sublines, as the haploid and chromosomal models predict. Quantitative evaluation shows that subdiploid models with a kinetic complexity of 860 or less are not compatible with the results. This experiment was not sensitive enough, however, to exclude subdiploid models if the kinetic complexity is 2000 or greater. Selection on heterozygotes also failed to provide evidence in favour of assortment. All the results are consistent with and support the diploid subunit model of theParameciummacronucleus.
Macronuclear DNA in Stentor coeruleus: a first approach to its characterization
Authors: Pelvat B. , De Haller G. 
Published: September 2009

SUMMARYThe macronuclei of Stentor coeruleus were isolated on a discontinuous sucrose gradient and their DNA was purified by conventional methods. The GC content was 32 mole%. The DNA banded as a single peak on analytical ultracentrifugation at 1·691 g/cm3. The molecular weight of the DNA was 5 × 106 to 4 × 107 daltons. Genome size determined by DNA–DNA reassociation kinetics was 6 × 1010 daltons. The macronuclear genome was mostly simple, about 85% being made of non-repetitive sequences.
Non-randomness of nucleotide bases in mRNA codons
Authors: Nassar R. F. , Cook R. D. 
Published: September 2009

SUMMARYMaximum likelihood estimates of codon and base frequencies from observed amino acid composition of proteins were obtained based on models capable of revealing dependency between base arrangements in the three positions of a codon. Results showed that many of the proteins analysed revealed dependency between base arrangements in the first and second codon positions (first-order interaction). Also, in a number of proteins the interactions between base arrangements seemed to involve simultaneously more than one first order interaction and/or a second-order interaction (among base arrangements in the three codon positions). It was of interest to observe that the model of random base arrangements did not fit the observed amino acid data in almost all of the proteins that were analysed. More than ten amino acids contributed to this deviation from randomness.
Combined chromosomal and plasmid encoded control for the degradation of phenol inPseudomonas putida
Authors: Wong C. L. , Dunn N. W. 
Published: September 2009

SUMMARYThe TOL(M1) metabolic plasmid was transferred fromPseudomonas arvillamt-2 to a mutant ofPseudomonas putida. Although neither the donor nor the recipient could grow on phenol, the transconjugants could grow slowly on this carbon source. In these transconjugants phenol was converted to catechol by chromosomal encoded phenol hydroxylase followed by degradation of catechol by low uninduced levels of the plasmid encoded catecholmetacleavage pathway. A mutant, which grew well on phenol, was isolated from one of the transconjugants and it was found that phenol could now act as an inducer for themetacleavage pathway.
Genetic characterization ofrec-1, a mutant ofUstilago maydisdefective in repair and recombination
Authors: Holliday R. , Halliwell R. E. , Evans M. W. , Rowell V. 
Published: September 2009

SUMMARYDetailed physiological and genetic studies of haploid and diploid strains have revealed a complex phenotype for therec-1 mutation inUstilago maydis. The mutant is defective in the repair of damage by UV light, ionizing radiation and nitrosoguanidine. Four alleles are all recessive and have the same sensitivity to UV, suggesting the loss of a single cellular function. A significant fraction of non-viable cells is formed during growth, and in diploid strains considerable variation in colony size and morphology is seen. The spontaneous frequency of mutation is greater than in wild-type cells, but there is little, if any, enhancement by irradiation.rec-1 also has pleiotropic effects on genetic recombination. The spontaneous level of mitotic allelic or non-allelic recombination is abnormally high, but the relative increase after irradiation is much lower than in control diploids. Allelic recombination is strongly associated with the expression of a hetozygous recessive distal marker, and it is shown that this is often due to hemizygosity rather than to homozygosity of this marker. The results indicate that allelic recombination is due to crossing over rather than gene conversion, but that the cross over is often associated with a chromatid break.rec-1 interacts with other radiation sensitive mutants, such asrec-2. Diploids homozygous for both are totally deficient in allelic recombination. In crosses betweenrec-1 strains meiosis is defective, with a low viability of meiotic products and frequent production of aneuploids or diploids among the survivors. The overall phenotype ofrec-1 strains can best be explained in terms of the loss of a regulatory function, which leads to uncontrolled recombination during mitosis and meiosis, and the loss of a recombination repair pathway which is normally induced by agents which damage DNA.
Genetic polymorphism and evolution in parthenogenetic animals: V. TriploidAdoxus obscurus(Coleoptera: Chrysomelidae)
Authors: Lokki Juhani , Saura Anssi , Lankinen Pekka , Suomalainen Esko 
Published: September 2009

SUMMARYThe genetic variability at 16 enzyme loci in 52 Scandinavian triploid parthenogenetic populations of the beetleAdoxus obscurushas been studied by starch-gel electrophoresis. The overall genotypes of different beetles have been compared with each other and with a sample from a diploid bisexual population from Canada. Eighty per cent of the parthenogenetic beetles have the same overall genotype. The remainder belong to six genotypes, three of which are found in only one population. The variability within and between parthenogenetic populations ofA. obscurusis much lower than in other comparable parthenogenetic insects studied by us. This is interpreted to be a consequence of the efficient migration of the genotypes with the highest fitness, leading to a replacement of less-adapted genotypes.A. obscurusis a flying insect, whereas the other parthenogenetic insects studied by us are sluggish flightless forms.
Aneuhaploids in bread wheat
Authors: Miller T. E. , Chapman Victor 
Published: September 2009

SUMMARYEuploid and aneuploid plants ofTriticum aestivum, variety Chinese Spring were pollinated with, pollen ofHordeum bulbosum. Euhaploids and aneuhaploids of Chinese Spring were obtained from the crosses. Meiotic chromosome pairing was analysed in 25 different aneuhaploids and the results were compared with those obtained from euhaploids. The evidence provided by the meiotic studies was used to identify chromosomes whose activities affected the genetic control of chromosome pairing.Meiosis was abnormal in a 23-chromosome aneuhaploid and in the 22-chromosome sectors of a chimaeral plant. Both plants were thought to have resulted from the incomplete elimination of the genome ofH. bulbosumfrom hybrid embryos. It is suggested that the meiotic abnormalities in the two aneuhaploids were caused by the residual barley chromosomes.
The lactose system ofKlebsiella aerogenesV9A: 5. Lac-permease defective mutants of twoKlebsiellaLac plasmids and their apparent reversion to wild type
Authors: Reeve E. C. R. 
Published: September 2009

SUMMARYThe Lac plasmids in twoKlebsiellastrains, V9A and RE1544, give characteristic Lac-permease defective mutations which produce a lactose-negative (ML−) phenotype in the host strain, in spite of the presence of alacoperon on the chromosome. These ML−clones can revert to the wild-type (ML+) phenotype, and the mechanism of this reversion is examined. In V9A carrying its own Lac plasmid (FKlac), it is shown that reversion of ML−to ML+is usually the result of mutation to constitutivity of one of two galactoside permeases which are not induced by lactose but accumulate lactose when otherwise induced or made constitutive. However, in one out of the 51 ML+revertants tested the mechanism of reversion appeared to be a change back to wild type of the Lac plasmid's own permease gene. In V9A carrying the Lac plasmid (pRE6) from RE1544, successive changes of phenotype were obtained of ML+to ML−to ML+to ML−to ML+; these were all found to be the result of changes in the plasmid permease gene, and could be simply explained if an IS sequence could insert and excise from this gene.
Suppressor-specificity of antisuppressors in yeast
Authors: McCready Shirley J. , Cox Brian 
Published: September 2009

SUMMARYEighteen mutations ofSaccharomyces cerevisiae, at eight loci, isolated as antisuppressors ofSUPQ2, an ochre-suppressing allele ofSUP11, were crossed with three other suppressors.They were found to abolish the ability ofSUP2(inserting tyrosine), to suppress the ochre mutationsade2.1andcan1.100, but not its ability, to suppresshis5.2orlys1.1.When coupled with any antisuppressor,SUPQ5, inserting serine, was also unable to suppressade2.1, but the suppression of other ochre mutations varied from oneasu-SUPQ5strain to another. No antisuppressor affected the ability ofSUP11-am, an amber-suppressing allele ofSUP11, to suppresstrp1.1, an amber mutation.
On the dynamics of activation of mammalian X chromosomes
Authors: Mukunda N. , Chandra H. Sharat , Gadgil Madhav , Rajagopal A. K. , Sudarshan E. C. G. 
Published: September 2009

SUMMARYWe have investigated a mathematical model of the process of activation of the X chromosomes in eutherian mammals. The model assumes that the activation is brought about over some definite time interval T by the complete saturation of N receptor sites on an X chromosome by M activating molecules (or multiples of M). The probability λ of a first hit on the receptor site is considered to be very much lower than that of subsequent hits; that is, we assume strong co-operative binding. Assuming further that an incomplete saturation of receptor sites is malfunctional, we can show that for proper activation of X chromosomes in normal diploid males and females, we must have λMT ≥ 3 and 0·96 ≤ N/M ≤ 1. An extension of this analysis for the triploid cases shows that under these conditions, we cannot explain the activation of two X's if the number of activating molecules is fixed at M. This suggests that there must be two classes of triploid embryos differing from each other in a step-wise manner in the number of activating molecules. In other words, triploids with two active X chromosomes would require 2M activating molecules as opposed to M molecules in triploids with a single active X. This interpretation of the two classes of triploids would be consistent with differing imprinting histories of the parental contributions to the triploid zygote.
The homoeologous relationships of rye chromosomes 4R and 7R with wheat chromosomes
Authors: Koller O. L. , Zeller F. J. 
Published: September 2009

SUMMARYBy means of rye chromosome CR from Imperial added to Chinese Spring wheat the alien substitutions 4A/CR, 4A/CRS, 4B/CR, 4D/CR, 4D/CRS, 7A/CRL, 7B/CR, 7B/CRL, 7D/CR and 7D/CRLwere isolated. Substitutions 4A/CRSand 4D/CRShad a better fertility and vegetative vigour than the corresponding substitutions with the complete chromosome CR. In substitutions the entire chromosome CR did not compensate for the absence of wheat chromosomes of group 7, whereas the substitutions 7A/CRL, 7B/CRLand 7D/CRLwere more fertile than the corresponding nullisomics 7A, 7B and 7D. It was shown that the short arm of CR is homoeologous to wheat telosomes 4Aα, 4BLand 4DS, whereas most of the long arm of CR is homoeologous to the wheat arms 7AS, 7BSand 7DS. Rye chromosome CR is designated 4R. Only three substitutions with rye chromosome DR were produced. The fertility of substitutions 7A/DR and 7B/DR were considerably lower than that of nulli-7A and nulli-7B. The 4B/DR substitution was sterile. Rye chromosome DR is believed to be a double interchanged chromosome in comparison to the correspondingSecale montanumchromosomes. Rye chromosome DR is designated 7R. On the basis of substitution ability of CR and DR and several homoeologous gene loci on these chromosomes an evolutionary scheme for the derivation of theSecale cerealegenome fromSecale montanumis outlined.
Inheritance of sperm head abnormality types in mice – the role of the Y chromosome
Authors: Krzanowska Halina 
Published: September 2009

SUMMARYFour inbred strains of mice were used, differing in the total percentages of spermatozoa with abnormal heads (KE, 22·1%; C57, 26·4%; KP, 7·7%; CBA, 5·5%) and in the frequency distribution of abnormality types, as divided into four arbitrary classes. The most variable class 2 (narrow heads with canals inside the nuclear material) accounted for 47% of all abnormalities in KE strain, was common in CBA (29%) and almost missing in KP and C57 strains. F1 hybrids from the diallel crosses of these strains exhibited highly significant heterosis effects and significant reciprocal differences in the total percentage of abnormalities. The relative frequency of class 2 ranked in F1 hybrids in a similar order as calculated from the mid-parental values. After seven generations of backcrosses performed to introduce the Y chromosome from CBA to the genetical background of the KE strain, the total percentage of abnormalities was significantly reduced, although the relative proportion of class 2 was similar to that in KE strain. Also the Y chromosome from C57 strain, introduced into the genetical background of KE strain, caused a significant reduction of total abnormalities, but again the relative frequency of class 2 was not affected. It is concluded that the Y chromosome plays an important role in determining the total percentage of sperm head abnormalities, but does not seem to be involved in influencing specific abnormality types.
Regressions between relatives
Authors: Bulmer M. G. 
Published: September 2009

SUMMARYA metric character determined by a large number of loci without epistasis is normally distributed. In the absence of linkage the joint distribution in two or more relatives is multivariate normal, so that all regressions are linear and have constant residual variance. In the presence of linkage this is no longer true except in the case of parent and child; for all other types of relatives the regression line is unaffected by linkage but the residual variance about this line is no longer constant but increases away from the mean.