bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitochondrial instability in a strain ofSaccharomyces cerevisiae
Authors: Evans I. H. , Wilkie D. 
Published: September 2009

SUMMARYA haploid strain ofSaccharomyces cerevisiaehas been described which, on glucose medium, segregates vegetatively a high frequency of mutants with different degrees of respiratory impairment. The range of mutants seemingly encompasses both non-revertible ρ- petites and revertible point mutations resembling leakymit- mutations. The segregants have aberrant cytochrome contents and reduced growth capabilities on fermentable sugars other than glucose; these defects apparently correlate with the degree of respiratory impairment. Genetic analysis of this mutator phenomenon has implicated a nuclear gene which appears to show specificity of interaction with the mitochondrial genome as well as a requirement for glucose repression. The mutator effect seems to extend also to the loci in mitochondrial DNA for resistance to the antibiotics erythromycin and oligomycin.
Strain variation in spermatozoal glycosidases in inbred mice
Authors: Self Steven J. , Winchester Bryan G. , Archer James R. 
Published: September 2009

SUMMARYTen glycosidases were measured in suspensions of spermatozoa from the vasa deferentia of two inbred mouse strains and their intercrosses. Eight of these glycosidases were associated with the sperm cells and all of these showed genetical variation between the strains except α-l-fucosidase with optimal activity at pH 5·4. In contrast liver enzyme activities showed no significant variation except α-l-fucosidase. Genetic studies indicated that the variation of spermatozoal β-d-hexosaminidase, α-d-mannosidase, α-l-fucosidase and β-d-galactosidase are inherited at autosomal loci and α-d-galactosidase variation showsX-linked inheritance. We propose a new provisional gene symbol (Afuc-2) for a spermatozoal variant of α-l-fucosidase.
Compatibility and sex specific phage plating characteristics of the TOL and NAH catabolic plasmids
Authors: White G. P. , Dunn N. W. 
Published: September 2009

SUMMARYThe sex specific bacteriophage PR4 has been found to plate onP. aeruginosastrains harbouring the TOL catabolic plasmid or the plasmid pND2 derived from TOL. Based on this, attempts were made to place TOL into aPseudomonasplasmid incompatibility group and by showing that pND2 is incompatible with the R plasmid R2, TOL has been placed into the P-9 group. The NAH catabolic plasmid has been reported to be incompatible with TOL, pND2 and a variety of other plasmids derived from TOL. Thus, these plasmids also would appear to belong to the P-9 incompatibility group.
Analysis of linkage disequilibria between allozyme loci in natural populations ofDrosophila melanogaster
Authors: Langley Charles H. , Smith Diana B. , Johnson F. M. 
Published: September 2009

SUMMARYLinkage disequilibria between pairs of 8 polymorphic enzyme loci (αGpdh, Mdh, Adh, Est-6, Pgm, Odh, Est-CandAcph) in some 100 natural population samples ofDrosophila melanogasterwere examined. The estimates of linkage disequilibrium were made from zygotic frequencies. The magnitude of linkage disequilibria are small and similar to those in previous reports. Variation in linkage disequilibrium among related subpopulations was analysed by analysis of variance of the correlation coefficients. Despite the small absolute value of linkage disequilibrium there is a suggestion of a correlation among related subpopulations. The magnitude of linkage disequilibrium was observed to be positively correlated with linkage. Two cage populations were observed to demonstrate large amounts of linkage disequilibrium between closely linked loci in contrast to the situation in natural populations. This is attributable to the finite sizes of these cage populations.
Does Muller's ratchet work with selfing?
Authors: Heller R. , Smith J. Maynard 
Published: September 2009

SUMMARYThe accumulation of deleterious mutations in a finite diploid selfing population is investigated. It is shown that the conditions for accumulation are very similar to those for the accumulation of mutations in an asexual population by ‘Muller's ratchet’. The ratchet is likely to operate in both types of population if there is a large class of slightly deleterious mutations.
Maternal effects on body weight in mice selected for large and small size
Authors: Al-Murrani W. K. , Roberts R. C. 
Published: September 2009

SUMMARYFertilized eggs were transferred reciprocally between large and small mothers, to study maternal effects on body weight in mice selected for large and small size, respectively. Prenatal maternal effects were not important in our material, but postnatal maternal effects were detectable. The postnatal effects accrued mostly from the inadequacy of small mothers for large offspring; small offspring were largely unaffected by the type of mother. Genetic maternal effects were only of limited importance; maternal influences of environmental origin arose from variation in litter size.
Characterization of a new choline locus inAspergillus nidulansand its significance for choline metabolism
Authors: Markham Paul , Bainbridge Brian W. 
Published: September 2009

SUMMARYA new locus for choline-requirement has been identified inAspergillus nidulansand designatedchoC3. It has been located to linkage group VIII at a position 31·9 ± 2·2 map units to the left of thesDlocus.It is proposed that this locus codes either for the enzyme that catalyses the transmethylation of phosphatidyl monomethylaminoethanol to phosphatidyl dimethylaminoethanol or for a molecule essential for the synthesis or function of this enzyme.
Effective method for the isolation of non-nodulating mutants ofRhizobium trifolii
Authors: Żurkowski Witold , Lorkiewicz Zbigniew 
Published: September 2009

SUMMARYNon-nodulating mutants ofRhizobium trifoliiwere found in cultures incubated at 35 °C for 7 days. From among ten strains incubated at the elevated temperature six became non-nodulating. The frequency of Nod−mutants inR. trifoliicultures varied from 1 to 75% depending on the strain tested. It is suggested that gene(s) controlling nodulation are located on a large plasmid.
Multiple allelism at the locus controlling warfarin resistance in the Norway rat
Authors: Greaves J. H. , Ayres P. B. 
Published: September 2009

SUMMARYTwo warfarin-resistant strains of the Norway rat, Rattus norvegicus, derived independently from wild populations in Wales and Scotland and both homozygous for a major gene at the warfarin-resistance locus, Rw, were found to differ in their hypoprothrombinaemic response to simultaneous dosage with warfarin and vitamin K. The Welsh strain gave a small response and the Scottish strain a large response. These two response levels segregated in Mendelian fashion in various crosses involving the two resistant strains and a third, non-resistant strain. This indicates that the Rw locus has a series of three multiple alleles, denoted Rww, Rws and Rw+. The results are discussed briefly in relation to biochemical, ecological and evolutionary aspects of warfarin resistance.
The relationship between t and H-2 complexes in wild mice: I. The H-2 haplotypes of 20 t-bearing strains
Authors: Sturm Sabine , Figueroa Felipe , Klein Jan 
Published: September 2009

SUMMARYTwenty t haplotypes were extracted from wild mice captured at several locations in Europe, Israel, North Africa, and South America. The haplotypes were designated tTuw1 through tTuw20. The H-2 haplotypes of the lines were defined using antisera and monoclonal antibodies specific for private antigenic determinants controlled by known H-2 alleles and by antisera produced using the new t lines as donors. The tTuw haplotypes fall into four groups according to the H-2 haplotype associated with them. Haplotypes tTuw10 through tTuw18 are associated with H-2W30, previously found to be linked with haplotypes of the tw1 group. Haplotypes tTuw1 through tTuw6 are associated with a new H-2 haplotype, H-2w36, characterized by the determinant H-2.107. Haplotypes tTuw7 through tTuw9 are associated with another new H-2 haplotype, H-2w37, characterized by determinants H-2.108 and H-2.111. And finally, haplotypes tTuw19 and tTuw20 are associated with yet another new H-2 haplotype, H-2w38, characterized by determinants H-2.33 and H-2.109. These findings suggest that the t polymorphism might be more extensive and more intricate than it was previously thought to be and that at least some of the t-associated H-2 haplotypes, and probably also the t haplotypes themselves, are related to one another in their origin.
Close linkage between albumin and vitamin D binding protein (Gc) loci in chicken: a 300 million year old linkage group
Authors: Juneja R. K. , Sandberg K. , Andersson L. , Gahne B. 
Published: September 2009

SUMMARYEvidence for close genetic linkage between the structural loci for serum albumin (Alb) and serum vitamin D binding protein (Gc) in chicken is presented. The results are based on a study of a single sire family comprising 36 informative offspring. No recombinants have been observed. It is concluded that this linkage in the chicken is homologous to the close linkage of the albumin and Gc loci reported in man and the horse. Thus, this linkage group has most probably been conserved for at least 300 million years.
Analysis of chromosome pairing and breakage in pearl millet
Authors: Koduru Prasad R. K. , Murthy T. G. K. , Lakshmi K. V. , Rao M. Krishna 
Published: September 2009

SUMMARYThe relationship between chromosome pairing and chromosome fragmentation has been studied in a gene controlled mutant of pearl millet (2n= 14). Premeiotic mitosis, premeiotic cell development and early prophase I are normal without any fragments, which first appear at pachytene. The extent of fragmentation varies from zero to very extreme with two discrete classes of plants, namely those with partial fragmentation and those with multiple fragmentation. A quantitative analysis of bivalent distribution and the distribution of AI bridges in desynaptic and fragmented cells show all of them to be nonrandom events. We suggest that in cells showing partial fragmentation the bridges and fragments result from U-type exchanges at pachytene. The reduced frequency of AII bridges indicates relatively low sister chromatid reunion at pachytene. In multiple fragmented plants numerous minute fragments were seen from pachytene. Despite these anomalies most PMCs complete meiosis but subsequently abort at the pollen grain stage. The mutant gene also causes disturbances in the sequence of meiotic development in the ear and in the synchronous development of PMCs within an anther. It has no effect on the tapetum or on the physiological development of the anther.
Increased sensitivity to cell killing and mutagenesis by chemical mutagens in thymidine-kinase-deficient subclones of a Friend murine leukaemia cell line
Authors: McKenna P. G. , Yasseen A. A. 
Published: September 2009

SUMMARYWild-type Friend murine leukaemia (clone 707) cells and two thymidinekinase-deficient subclones, 707BUE and 707BUF, were compared for sensitivity to killing and mutagenesis by the chemical mutagens, ethyl methane sulphonate (EMS),N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), mitomycin C (MMC), and methyl methane sulphonate (MMS). The two thymidine-kinase-deficient subclones were significantly more sensitive to killing by each of the four chemical mutagens than were wild-type cells. The increased sensitivity to killing by the four mutagens was also reflected in increased mutagenesis (per unit dose of mutagen) to 6-thioguanine resistance. In the light of these results, the significance of thymidine kinase in DNA repair and mutagenesis is discussed.
The phasmid as a tool for plasmid genetics: II. Isolation of point mutations that affect replication of a ColE1-related plasmid
Authors: Cesareni Gianni , Castagnoli Luisa , Brenner Sydney 
Published: September 2009

SUMMARYThe insertion of a high-copy-number plasmid into a lambdoid phage chromosome which lacks a functional repressor gene confers on the hybrid ‘phasmid’ the capacity to grow on an immune lysogen. This was found to be due to titration of repressor because of plasmid replication. We have exploited this property in order to isolate mutants that affect plasmid replication. These mutants have been mapped in a region that was previously characterized as necessary for plasmid replication and incompatibility properties. Some of the mutations could revert at frequencies characteristic of single-base-pair change mutations.
Genetic background affects expression of t haplotype in mouse sperm
Authors: Olds-Clarke Patricia , McCabe Susan 
Published: September 2009

SUMMARYTwo aspects of sperm phenotype were examined for tw32/+ males of the inbred strains C3H and C57BL/6 (B6). Sperm from fertile C3H-tw32/+ males very rarely achieved fertilization in vitro, while sperm from congenie C3H-+/+ males had no such difficulties. The presence of tw32 had no effect on ability of B6 sperm to undergo fertilization in vitro. In fertile hybrid males produced from crosses of B6 and C3H strains, tw32 significantly reduced, but did not inhibit completely, the sperms' ability to fertilize in vitro. The presence of tw32 decreased by a factor of two the frequency of abnormal sperm heads in males of the B6 strain, but doubled the frequency in the C3H strain. Hybrid males resembled the C3H strain in this respect. The presence of T or T2J had no effect on the level of sperm abnormalities in any strain. These results emphasize the importance of genetic background in expression of t haplotypes in sperm, and suggest that tw32 can influence a range of sperm characteristics, by interacting with products of other loci.
Genetic basis and natural variation of α-amylase isozymes in barley
Authors: Brown A. H. D. , Jacobsen J. V. 
Published: September 2009

SUMMARYTwo physiologically and biochemically distinct groups of α-amylase (E.C.3.2.1.1) isozymes are synthesized when isolated aleurone layers of barley are incubated with gibberellic acid (GA3). Isoelectric focusing of the α-amylases showed that the isoelectric points of the isozymes of one group were near pH 5, whereas those of the second group were close to pH 6. Using wheat–barley addition lines, the genes for these groups were located in barley chromosomes 1 and 6 respectively. Joint segregation in the F2 generation of appropriate crosses indicated that the isozymes within each group were inherited collectively, and were attributed to codominant alleles segregating at two presumably complex loci, α-Amy 2 and α-Amy 1.The extent of genetic variation at these two loci was examined in 40 lines of Hordeum spontaneum (the wild progenitor of barley), and in a complex gene pool representative of H. vulgare (composite cross XXI). Variation at the α-Amy 1 locus was much more extensive than that at the α-Amy 2 locus. The genetic variation at both α-amylase loci exceeded that at the majority of other allozyme loci. However the α-amylase loci were less variable than the two loci coding for the seed storage protein, hordein. The wild species was found to contain much genetic diversity, which might be useful in modifying α-amylase activity by breeding. Parallels between the genetics and variation of α-amylase in barley and wheat were noted.
Selection against harmful mutations in large sexual and asexual populations
Authors: Kondrashov Alexey S. 
Published: September 2009

SUMMARYSelection against harmful mutations in large populations is studied assuming that the rate of fitness decrease grows with every new mutation added to a genome. Under this reasonable assumption (Mayr, 1970) the average fitness of a sexual population, without linkage between the loci, is higher, and the average equilibrium number of harmful mutations per individual lower, than in an asexual population. If a gamete contains on the average one or more new mutations, the resulting advantage of sexual reproduction and recombination seems to be sufficient to counterbalance the double advantage of parthenogenesis. Moreover, selection against harmful mutations is probably the most powerful factor preventing linkage disequilibrium even with epistatic interaction between the loci.
Deletion mapping of theniiAniaD gene region ofAspergillus nidulans
Authors: Tomsett A. Brian , Cove David J. 
Published: September 2009

SUMMARYThe genetic fine-structure of theniiAniaD gene region ofAspergillus nidulanshas been studied using deletion mapping. Deletions were identified asniiAniaD double mutants and comprised 1% of spontaneous chlorate-resistant mutants. All such double mutants were shown to involve deletions and their frequency was not increased by mutagenic treatment with eitherN-methyl-N′-nitro-N-nitrosoguanidine or with ultraviolet light. Deletion maps of theniaD andniiA genes have been constructed. A further class of mutation was also mapped using the deletions. Thesecrnmutations, which affect a gene whose function is as yet unknown, map on the centromere proximal side ofniiA. This analysis of a eukaryote gene cluster will provide a framework upon which to base studies of the regulation of the nitrate assimilation pathway.
Temperature-sensitive mutants ofPhysarum polycephalum– expression of mutations in amoebae and plasmodia
Authors: Burland Tim , Dee Jennifer 
Published: September 2009

SUMMARYOver 100 temperature-sensitive mutants ofmt-h (apogamic) strains ofPhysarum polycephalumwere isolated either by testing clones of mutagenized amoebae (ATS mutants) or by the more laborious method of testing plasmodia derived from such clones (PTS mutants). When amoebae and plasmodia of each mutant were tested for growth temperature sensitivity on different media (to give optimum growth of each phase), only 21% of 73 ATS mutants and 32% of 31 PTS mutants appeared to be temperature-sensitive in both phases, suggesting that the majority of mutants are phase-specific, as concluded from several similar studies by previous authors. When the mutants were tested on a third medium which allows growth of both amoebae and plasmodia, many of the mutants no longer had a temperature-sensitive phenotype in either phase. Among the remainder, 51% of ATS mutants and 67% of PTS mutants were temperature-sensitive in both phases. It was suggested that certain media have a remedial effect on some temperature-sensitive mutants so that the phenotype is apparently normal. Thus, the proportion of phase-specific mutants may be over-estimated if tests of temperature-sensitivity are done on the different media commonly used for culture of amoebae and plasmodia respectively. It was concluded that the most efficient procedure for isolation of temperature-sensitive mutants expressed in plasmodia is to screen clones of amoebae on a medium resembling as closely as possible that which is to be used for testing plasmodia.
The functional units of macronuclear assortment inTetrahymena thermophila
Authors: McCoy J. Wynne 
Published: September 2009

SUMMARYMacronuclei assorting simultaneously forH, Chx, Mpr, andco, and containing only one or two copies of theHDallele produced several combinations of phenotypes at the other loci, instead of only one or two such combinations. It follows that macronuclear subnuclei, if they exist at all, must frequently exchange parts. Models involving somatic recombination, transient subnuclei, or progressive chromosome fragmentation are discussed as possible explanations.
Variability in the timing and outcome of macronuclear assortment inTetrahymena thermophila
Authors: McCoy J. Wynne 
Published: September 2009

SUMMARYNew experimental designs have detected unexpectedly large variations in the time at which macronuclear assortment begins, and in the ratios of the stabilized products. Variation is detected between strains, and, within strains, between conjugating pairs. TheChxlocus gave results ranging from late assortment (40–60 fissions) to early assortment with skewed input, indicating the existence of some relation between the parameters of input ratio and time of determination.
Embryonic bone growth in lines of mice selected for large and small body size
Authors: Blakley Ann 
Published: September 2009

SUMMARYEmbryonic tibia growth was measured in large, small and control mouse embryos in situ and in organ culture. In situ tibias of the large line were longer than controls which were longer than tibias of the small line. Relative growth was approximately equal among lines. In culture tibias of the small line grew more than controls and as much as or more than tibias of the large line. Embryonic genotype appears to be more important in regulating tibia growth than uterine environment. Humoral differences among lines may influence tibia growth.
Genetic regulation of differentiation inPhysarum polycephalum
Authors: Honey N. K. , Poulter R. T. M. , Teale D. M. 
Published: September 2009

SUMMARYPlasmodial formation in the MyxomycetePhysarum polycephalumis controlled by a mating type (mt) locus. There are a number of different heterothallicmtalleles; and also a variant,mth, that allows plasmodial formation in pure clones. This paper reports an analysis of this differentiation system. The strainCL(mth) forms plasmodia in pure clones (i.e. it selfs).CLwas mutagenized with NMG and 21 mutants unable to differentiate into amoebae were isolated. The mutants, together withCLd, fell into two complementation groups, twelve indifAand ten indifB. Both complementation groups are closely linked or allelic to themtlocus.difArepresents a gene essential for plasmoclial formation, but it is suggested thatdifBrepresents a class of revertants to themt2heterothallic state. A model of the control of plasmodial formation is proposed in which themtlocus is suggested to code for the repressor of thedifAgene. Genetic control is explained in terms of the dilution of allele-specific repressors.
A mechanism for RNA–RNA splicing and a model for the control of gene expression
Authors: Murray Vincent , Holliday Robin 
Published: September 2009

SUMMARYA mechanism for RNA–RNA splicing is proposed. A species of RNA (‘splicer’ RNA) hybridizes to precursor mRNA across the splice point. This hybridization can be with intron or exon sequences or both. The double-stranded RNA structure precisely indicates to the splicing enzymes the exact location for exon ligation.A model for the control of gene expression is presented. The regulation of synthesis of different splicer RNAs will also control which precursor mRNA molecules are spliced. The removal of intervening sequences from a precursor mRNA molecule could be both a signal for that molecule to be transported to the cytoplasm and a means of allowing gene expression.
Heritability of cranium bifidum and spina bifida in the golden hamster
Authors: Moffa A. M. , White J. A. 
Published: September 2009

SUMMARYThe heritability (h2) and frequency of the neural tube closure defects, cranium bifidum (CB) and spina bifida (SB), have been estimated for a population of 9-day-old hamster embryos through half-sibling analysis. The average frequency of the total affected embryos per litter is approximately 17% while the pooled estimate forh2based on between sires and between dams within sires components was 4%. This value points to the importance of environmental factors in contributing to the variance in defect frequencies observed within this population.
R.SmaI cleavage map of the transfer region of theE. coliK12 sex factor F
Authors: Willetts Neil , Johnson Gillian 
Published: September 2009

SUMMARYA map of the seventeen R.SmaI sites within the 33·4 kb transfer region of plasmid F has been obtained. The number of R.SmaI sites contrasts sharply with the few sites for other restriction endonucleases with hexanucleotide specificity. Location of the R.SmaI sites in γtratransducing phages allowed physical location of lambda insertions into thetraB,traFandtraHgenes.