bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence on the nature and complexity of the mechanism of chiasma maintenance in maize
Authors: Maguire Marjorie P. 
Published: September 2009

SummaryInferences on the mechanism of chiasma maintenance can be drawn from study of the distribution and frequency of chiasma-like associations between bridges and fragments and between normal chromatids and fragments in meiotic material heterozygous for paracentric inversions. These bridges and fragments are the result of crossing over within the inverted region so that differing predictions for the associations are generated by the various models for chiasma maintenance mechanism. Results of such a study in material heterozygous for a large paracentric inversion in the long arm of chromosome 1 in maize are reported here. Findings are generally consistent with predictions of the ‘generalized sister chromatid cohesiveness model’, but are markedly at odds with the ‘binder only at specific crossover sites model’, and with the ‘late effective doubling of telomeres model’. Some of the results do not conform quantitatively to predictions of the ‘generalized sister chromatid cohesiveness model’ for a linear relationship between potential extent of sister chromatid cohesiveness and frequency of maintained association, suggesting additional complexity.
Parental influences on X chromosome expression
Authors: Forrester Lesley M. , Ansell J. D. 
Published: September 2009

SummaryUsing mice that were mosaics for both Xce and phosphoglycerate kinase (Pgk-1) alleles, we have established that the parental source of the Xce gene may affect the probability with which the X chromosome carrying it will remain active. This effect was seen in one allelic combination of Xce but not in another. The relationship between these effects and other phenomena of maternal ‘imprinting’ is discussed.
Polymorphism of lactate dehydrogenase B subunit in rat erythrocytes
Authors: Stolc V. 
Published: September 2009

SummaryLactate dehydrogenase regulator geneLdr-1controls the amount of the lactate dehydrogenase A subunit in rat serum and the amount of lactate dehydrogenase B subunit in rat erythrocytes because no recombinant rats were found among 295 pups produced in the BDIV × (ACI × BDIV)F1 and (ACI × DI) Fl × DI backcrosses. Two alleles regulate the high (Ldr-1a) and low (Ldr-1b) activity enzyme. TheLdr-1is not linked to hooded coat pattern or glyoxalase-1. Sex andLdr-1assorted independently; hence the gene is autosomal.
A new spontaneous mutation at the tufted locus within a mousethaplotype
Authors: Silver Lee M. , Cisek Lois , Jackson Catherine , Lukralle Deborah 
Published: September 2009

SummaryWe report here the occurrence of a new spontaneous mutation at the tufted locus present within the crossover-suppressed region of the completethaplotypefwLub1This new tufted allele shows complete expressivity of the tufted phenotype without any apparent effect on viability or reproduction. The presence of a tufted mutation within athaplotype that is cytologically marked by a Robertsonian translocation is particularly useful in genetic experiments aimed at understanding the structure and function ofthaplotypes.
Transcriptional organization of the Tra2 region controlling conjugational transfer of the narrow host rangePseudomonas aeruginosaplasmid R91–5
Authors: Moore R. J. , Krishnapillai V. 
Published: September 2009

SummaryThe transcriptional organization of the Tra2 region controlling conjugation by the narrow host range plasmid R91–5 ofPseudomonas aeruginosahas been determined. This region of 15·2 kilobase pairs of DNA encodes ten cistrons and specifies the synthesis and functionality of sex pili. The order of the cistrons was previously shown to betraW, (S, Z),U, (V, R),Q, T, Y, X(those within parentheses could not be ordered with respect to each other). The organization was determined by complementation tests for the restoration of plasmid transfer between transposon Tn7or Tn501induced insertion mutants and point mutants representative of the ten cistrons. Polarity mutations induced by Tn7permitted the identification of three operons. CistronstraW, Z, S, U, V, RandQformed a large operon with transcription postulated to be in that order. The second consisted oftra Tandtra Yalso in that order and the third consisted of only one cistron,traX. Polarity was not observed with Tn501insertions as they still permitted full expression of cistrons distal to the site of insertion with respect to the proposed promoter. Despite the unexpected behaviour of this transposon it nevertheless led to the identification of two previously unidentified cistrons,traOandtraPbeing betweentraZandSandtraRandV, respectively.
The genetic control of triosephosphate isomerase of hexaploid wheat and other Triticeae species
Authors: Pietro Michael E. , Hart Gary E. 
Published: September 2009

SummaryThe zymogram phenotypes of triosephosphate isomerase (TPI) were determined for a large number of aneuploid derivatives of Triticum aestivum cv. ‘Chinese Spring’ and for six wheat-alien species chromosome addition series. Examination of the available compensating nullisomic-tetrasomic and homoeologous groups 3 and 5 ditelosomic lines of Chinese Spring disclosed that T. aestivum possesses two systems of dimeric TPI isozymes, designated TPI-1 and TPI-2. The genes TPI-A1, TPI-B1 and TPI-D1 were located in Chinese Spring chromosome arms 3Ap, 3Bp and 3Dp, respectively and the genes TPI-A2, TPI-B2 and TPI-D2 in chromosome arms 5Aq, 5Bq and 5Dq, respectively. TPI-1 genes were also located in Hordeum vulgare cv. Betzes chromosome 3H, T. longissimum chromosome G, Elytrigia elongata chromosome 3E, and Secale cereale cvs. Imperial and Dakold chromosome 3R. TPI-2 genes were found in Betzes chromosome 5H, T. umbellulatum chromosome 5U, T. longissimum chromosome F, and Imperial and Dakold chromosome 5R. These gene locations provide evidence of homoeology between the alien chromosomes in which the genes are located and the chromosomes of homoeologous groups 3 and 5 of Chinese Spring, respectively. Evidence was obtained for the presence of a TPI-R2 gene in each of the T. aestivum cv. Kharkov -S. cereale cv. Dakold chromosome addition lines studied suggesting that this gene is present in the wheat genome in each member of this addition series.
Introgression of extranuclear genomes in finite populations: nucleo-cytoplasmic incompatibility
Authors: Takahata Naoyuki 
Published: September 2009

SummaryA ‘two locus two allele’ model is developed with special reference to the introgression of extranuclear genomes between two species of finite size. The model assumes that one locus, coded by a nuclear genome, causes the reproductive barrier while the other locus, coded by an extranuclear genome, causes nucleo-cytoplasmic incompatibility in particular genotypes. To fully study this model, simulations are conducted, and a diffusion equation is derived when introgression or extranuclear gene flow occurs in one direction. It is shown that although selection against the nuclear genome can reduce the levels of extranuclear gene flow and retard the introgression process, the dynamics are very similar to those without such selection. In contrast, the nucleo-cytoplasmic incompatibility directly affects the dynamics of introgressing extranuclear genomes: in large populations the ability of incompatibility to overcome extranuclear gene flow is conspicuous, but in small populations it is overshadowed by random sampling drift. Paternal leakage of extranuclear genomes, if present, is of evolutionary importance only when the male's migration rate is much larger than the female's. When the sizes of two populations are unequal, the introgression is most likely to occur from the larger population to the smaller one in the absence of mating preferences of backcross progeny. Recent observations on interspecific mitochondrial transfer in various species do not support the ubiquitousness of nucleo-cytoplasmic incompatibility as an efficient reproductive barrier.
Glucose-6-phosphate dehydrogenase expression in heterozygous kangaroo embryos and extra-embryonic membranes
Authors: Johnston P. G. , Robinson E. S. 
Published: September 2009

SummaryThe electrophoretic expression of the X-linked enzyme glucose-6-phosphate dehydrogenase was examined in heterozygous Macropus robustus embryos and their extra-embryonic membranes. The amnion and allantois, like the somatic tissues of the embryo proper, showed paternal X inactivation while the avascular and vascular yolk sac cells showed evidence of activity of both maternal and paternal alleles.
Recombination between thet6complex and linked loci in the house mouse
Authors: Nadeau Joseph H. , Phillips Sandra J. , Egorov Igor K. 
Published: September 2009

SummaryRecombination between thet6complex, three allozyme-encoding loci, two antigen-encoding loci, and four molecular markers was studied. The allozyme-encoding loci were complement component-3 (C-3), kidney catalase (Ce-2), and glyoxalase-1 (Glo-1); the antigen-encoding loci were theH-2Class I genesH-2KandH-2D; the four molecular markers wereTu66, an α-globin pseudogene (Hba-4ps), an unidentifiedH-2Class I gene, and theH-2ClassIIgene I-Aβ. The latter six loci were used as markers for thetcomplex. Recombination was detected betweenGlo-1,Ce-2andC-3, but not between the markers for thetcomplexTu66,Hba-4ps, and theH-2loci. These data indicate thatCe-2andC-3are located outside thet6complex, while the latter are located within. These data also indicate that the telomeric boundary of thet6complex is located betweenH-2andCe-2. Recently published studies have shown that complete gametic disequilibrium exists between thetcomplex and loci located centromeric to theH-2-Ce-2interval, while disequilibrium was not detected between loci located telomeric to this interval. Loci included within the region of recombination suppression are also those in disequilibrium with thetcomplex. As a result, recombination suppression probably resulting from chromosomal rearrangements associated with thetcomplex appears to be a sufficient explanation for the gametic disequilibrium observed between certain loci and thetcomplex.
Covariance between direct and maternal genetic effects in mice, with a model of persistent environmental influences
Authors: Riska Bruce , Rutledge J. J. , Atchley William R. 
Published: September 2009

SummaryCovariance between direct and maternal genetic effects on body weight in random-bred ICR mice at 2 through 10 weeks of age was estimated from cross-fostering experiments. The covariance contributes only a few percent of phenotypic variance at 2 weeks, but increases to 10–15% at later ages. Nearly all estimates are positive. We suggest that genes active during later parts of growth affect maternal performance more than those active during early growth, causing increased covariance at later ages. A model of combined genetic and persistent environmental effects on maternal performance is presented. Persistent effects of genetic or environmental variation in recent ancestors can influence covariance between relatives and response to selection.
Polymorphism from environmental heterogeneity: models are only robust if the heterozygote is close in fitness to the favoured homozygote in each environment
Authors: Hoekstra Rolf F. , Bijlsma R. , Dolman A. J. 
Published: September 2009

SummaryThe lack of robustness of models of the maintenance of polymorphism in a heterogeneous environment which has been pointed out by Maynard Smith & Hoekstra (1980), applies also to models based on habitat selection, on temporal variation and on density-regulated selection. Only if (partial) dominance ‘switches’ between environments such that the fitness of the heterozygote is always close to the favoured homozygote, is there reasonable robustness. This is true for all models considered. It is argued that there are good reasons for supposing that the favourable allele at a locus may show dominance, although the experimental evidence is still scanty.
Glu-B2, a storage protein locus controlling the D group of LMW glutenin subunits in bread wheat (Triticum aestivum)
Authors: Jackson Elizabeth A. , Holt Linda M. , Payne Peter I. 
Published: September 2009

SUMMARYGenes controlling the synthesis of the D group of low-molecular-weight (LMW) subunits of glutenin occur on the short arms of chromosomes 1B and 1 D. Their position on chromosome 1 B, relative to the storage protein lociGlu-B1(long arm) andGli-B1(short arm), was estimated by analysing the backcross-one progeny of two different crosses. To estimate recombination between the D subunit genes andGli-B1, half grains were analysed by two-dimensional electrophoresis. TheGli-B1locus contains genes for the B group of LMW glutenin subunits, γ-gliadins and ω-gliadins although only the latter were made use of in this study to distinguish the parental alleles. Additionally, the complementary half grains were analysed by sodium dodecyl sulphate, polyacrylamide-gel electrophoresis to estimate recombination betweenGli-B1andGlu B1, coding for high-molecular-weight (HMW) glutenin subunits. The D subunit genes occur at a new locus, provisionally defined asGlu-B2, which lies in betweenGlu-B1andGli-B1, 17 cM from the former and 22 cM from the latter. On the basis of previous mapping data involvingGli-B1, it was concluded that the D subunit genes occur close to the nucleolar organizing region and probably on the short-arm satellite, likeGli-B1.
Extension of the Haldane-Muller principle of mutation load with application for estimating a possible range of relative evolution rate
Authors: Ishii Kazushige , Matsuda Hirotsugu 
Published: September 2009

SUMMARYThe Haldane-Muller principle of mutation load is generalized so as to be applicable to both cases of strong and very weak selection with any time variation. It is proved that in an infinite asexual haploid population, theaverageMalthusian parameterm¯of a population, the evolution rate ν, and the total mutation rate μ satisfy the relation ∂m¯/∂/∂μ = ν/μ−1, so long as each Malthusian parameter is independent of μ. A similar result is also true in a diploid population under genie selection. It is discussed how the above relation gives a restriction on the possible range of values of relative evolution rate ν/μ.
Segregation and pairing of compound fifth-chromosomes inLucilia cuprinamales
Authors: Foster G. G. , Maddern R. H. 
Published: September 2009

SUMMARYVariability in fertility in compound chromosome (CC) strains ofLucilia cuprina(Wiedemann) is directly correlated with the segregation properties of the CCs in those strains. In compound fifth-chromosomes, high fertility (up to 50% ) is associated with high frequencies of segregation of the left element (C(5L)) from the right element (C(5R)) in males, while low fertility (up to 25%) is associated with random assortment of the CCs in males. Regular segregation ofC(5L) andC(5R) chromosomes in males is associated with particularC(5L) elements, which contain cytologically visible duplications of5Rchromatin. These duplications may contain a site which is normally involved in the pairing of the fifth chromosomes in males.In females the CCs segregate from one another with a frequency of 89%. None of theC(5R) elements studied affected segregation in males, and neitherC(5L) norC(5R) elements had any demonstrable effect on segregation in females. Transmission of certain CC elements through one or both sexes is significantly lower than expected. This could have a variety of causes, such as meiotic drive, inviability associated with position effects, or homozygosis of deleterious mutations on homologous CC arms during meiotic crossing over in females. The CC strains released during a field trial of genetic control contained both high-fertility and low-fertilityC(5L) chromosomes. Both types of CC were subsequently recovered from individuals which had overwintered in the field. Over a period of several generations following this recolonization one particular high-fertilityC(5L) chromosome increased in frequency to near-fixation, despite the presence in this chromosome of deleterious mutations.
Genetic studies of three sibling species ofDrosophilawith relationship to theories of speciation
Authors: Coyne Jerry A. 
Published: September 2009

SUMMARYDrosophila melanogaster,D. simulansandD. mauritianaare closely related species, the first two cosmopolitan and the last restricted to the oceanic island of Mauritius.D. simulansandD. mauritianaare the most closely related pair, with the latter species probably resulting from a founder event. The relatedness of the three species and their ability to hybridize allow tests of recent theories of speciation. Genetic analysis of two characters differing betweenD. simulansandD. mauritiana(sex comb tooth number and testis colour) show that the differences are due to at least five and three loci respectively. Behavioural tests further demonstrate that sex combs are probably used by males at a crucial step in mating, and that the differences between the two species may be related to differences in their mating ability. These genetic studies and previous work indicate that differences among these species are polygenic and not (as proposed by recent theories) attributable to only one or two loci of large effect. Further studies of interspecific hybrids show that genetic divergence leading to developmental anomalies is more advanced in the older species pairD. simulans/D. melanogaeterthan in the younger pairD. simulans/D. mauritiana. This supports the neo-Darwinian contention that reproductive isolation is one step in a continuous process of genetic change among isolated populations, and does not support current theories that such change occurs only during the evolution of reproductive isolation. Finally, investigations of the degree of gonadal atrophy and its sensitivity to temperature inD. simulans/D. mauritianahybrids fail to support recent speculations that phenomena similar to hybrid dysgenesis (which causes such atrophy inD. melanogaster) play a role in speciation.
Origin and diversity of mutants controlled by theUqtransposable element system in maize
Authors: Pereira Andy , Peterson Peter A. 
Published: September 2009

SUMMARYThree transposable element mutations, displaying an unstable pheno-type at theAlocus, were isolated from lines exhibiting Aberrant Ratio behaviour that originated from maize plants treated with plant RNA viruses. Each of these three unstable mutants is shown to belong to theUq-ruqtransposable element system. The two new mutants, along with the previously describeda-ruqmutant, are nonautonomous in mutability control in that the control of mutability is governed by the segregatingUqregulatory element. By following the distribution of differentUqelements segregating in independently derived genetic lines and utilizing tests of allelism and linkage, certain lineages ofUq-element-containing lines are revealed.
Clonal relationships among naturally occurring nicotinamide-requiringSalmonella typhimurium
Authors: Barker Ruth M. , Yousuf A. A. 
Published: September 2009

SUMMARYSalmonella typhimuriumstrains of biotype 25x have been shown in transductional cross experiments to be clonal in the Nad character. The ancestral bacterium, probably of biotype 25a, mutated to a requirement for nicotinamide and subsequently diversified in phage type and secondary biotype characters. Such a sequence of events indicates interconversion among phage types 6, 16, 46, 49, 73, 76 and 135. Strains in biotypes 1x, 9ix, 17x, 17dx, 19dx and 25hix yielded Nad+recombinants in interbiotype crosses, suggesting that each originated as an independent mutant line.
Genetic differences between substrains of the inbred mouse strain 101 and designation of a new strain 102
Authors: West John D. , Lyon Mary F. , Peters Josephine , Selby Paul B. 
Published: September 2009

SUMMARYGenetic polymorphisms revealed two distinct substrains of the inbred strain 101. One group included substrains 101*/Rl, 101/H and 101/HOxe; the other group comprised 101/El and 101/Sl. The two groups differed at 5 of the 8 genetic loci tested. The accompanying paper (Evans, Burtenshaw & Adler, 1985) shows that the two groups also differ for several chromosome polymorphisms. We suggest that genetic contamination occurred during the derivation of 101/El from 101/Rl and was already present in 101/El when 101/Sl was produced from this substrain. We further propose that these substrains be renamed 102/El and 102/Sl respectively.
Genetic analysis of the right (3′) end of the rosy locus inDrosophila melanogaster
Authors: Clark S. H. , Hilliker A. J. , Chovnick A. 
Published: September 2009

SUMMARYPrior reports from this laboratory have described the experimental basis for our understanding of the rosy locus (ry: 3–52·0) ofDrosophila melanogasteras a bipartite genetic entity consisting of a structural element that codes for the xanthine dehydrogenase (XDH) peptide and a contiguouscis-acting control element immediately to the left of the structural element. Although the left end (5′) of the structural element has been well defined, the right boundary (3′) has been given only casual treatment in our prior reports. In our recent studies of rosy locus expression we have been concerned with the production and identification of mutations in the non-structural regions immediately flanking the structural element. An improved definition of the right end of the structural element is essential to this analysis. In addition to producing a better definition of the right boundary of the structural element, this study produced several phenotypically novel mutations. These mutations were classified initially ascontrol element mutations, but upon analysis were found to map within the rosy structural element.Noevidence was obtained for the existence of a control element contiguous with the right end of the structural element.
Induction of recessive lethal mutations in theT/t–H-2region of the mouse genome by a point mutagen
Authors: Shedlovsky Alexandra , Guenet Jean-Louis , Johnson Lawrence L. , Dove William F. 
Published: September 2009

SUMMARYTheT/t–H-2region on mouse chromosome 17 is known from complex natural variants (‘t-haplotypes’) to contain numerous genes, including some affecting the immune system and the development of the embryo. Rapid progress in the isolation of recombinant DNA clones for this 50 megabasepair region is generating the material for its complete molecular anatomy. A crucial step in revealing the biological functions controlled by the region is to obtain mutants in which genes are inactivated individually. We have used a pair of inbred mouse strains and a series of classical breeding schemes that permit the detection of recessive lethal and detrimental mutations in theT/t–H-2region.In this initial phase of our study, 280 gametes mutagenized in the male germ line by ethylnitrosourea (ENU) have yielded eleven independent pre-natal recessive lethal mutations. Four have been mapped againstTmutations and have been shown to complement one another in all pairwise combinations.
Persistence of an alcohol dehydrogenase thermostable variant in a natural population ofDrosophila melanogaster
Authors: Hernández M. , Padrón G. , Cabrera V. M. 
Published: September 2009

SUMMARYA temporal survey of the alcohol dehydrogenase locus in a natural population ofDrosophila melanogasterfrom the Canary Islands has revealed the existence of an electrophoretic Fast thermostable variant, mapped within 0.8 units of the structuralAdhlocus, and which persists over a 6-year period with a frequency ranging from 0.8 to 0.5%.