bluuebunny/crossref_metadata_2025_split huggingface dataset:
Individual differences in children's understanding of inversion and arithmetical skill
Authors: Gilmore Camilla K. , Bryant Peter 
Published: May 2006

Background and aims. In order to develop arithmetic expertise, children must understand arithmetic principles, such as the inverse relationship between addition and subtraction, in addition to learning calculation skills. We report two experiments that investigate children's understanding of the principle of inversion and the relationship between their conceptual understanding and arithmetical skills.Sample. A group of 127 children from primary schools took part in the study. The children were from 2 age groups (6–7 and 8–9 years).Methods. Children's accuracy on inverse and control problems in a variety of presentation formats and in canonical and non‐canonical forms was measured. Tests of general arithmetic ability were also administered.Results. Children consistently performed better on inverse than control problems, which indicates that they could make use of the inverse principle. Presentation format affected performance: picture presentation allowed children to apply their conceptual understanding flexibly regardless of the problem type, while word problems restricted their ability to use their conceptual knowledge. Cluster analyses revealed three subgroups with different profiles of conceptual understanding and arithmetical skill. Children in the ‘high ability’ and ‘low ability’ groups showed conceptual understanding that was in‐line with their arithmetical skill, whilst a 3rd group of children had more advanced conceptual understanding than arithmetical skill.Conclusions. The three subgroups may represent different points along a single developmental path or distinct developmental paths. The discovery of the existence of the three groups has important consequences for education. It demonstrates the importance of considering the pattern of individual children's conceptual understanding and problem‐solving skills.
Evidence for the effectiveness of the Early Literacy Support programme
Authors: Hatcher Peter J. , Goetz Kristina , Snowling Margaret J. , Hulme Charles , Gibbs Simon , Smith Glynnis 
Published: May 2006

Background. It is widely recognized that effective interventions for poor reading involve training in phoneme awareness and letter‐sound knowledge, linked in the context of reading books. From the applied perspective, it is important to gather data on the effectiveness of different forms of implementation of literacy support within this framework.Aim. We evaluate the effectiveness of the UK Early Literacy Support (ELS) programme (Department for Education and Skills [DfES], 2001) relative to a programme of Reading Intervention based on ‘sound linkage’ (Hatcher, Hulme, & Ellis, 1994).Sample. The sample comprised 128 6‐year‐old children, from 16 primary schools in a Local Education Authority (LEA) in the north of England.Method. The children were nominated as in need of special help by their class teachers and allocated to one of the two programmes.Results. After controlling for a difference in spelling ability at the start of the intervention, it was found that both groups of children made equivalent and significant gains in reading and spelling that were maintained at follow‐up. The standardized scores were in the average range. Regression analyses confirmed the importance of initial reading ability as well as letter identification, phoneme manipulation, and sound linkage in predicting progress in learning to read and to spell.Conclusion. The ELS programme provides a cost effective method of boosting 6‐year‐old children's reading to an average level.
Observation of children with attention‐deficit hyperactivity (ADHD) problems in three natural classroom contexts
Authors: Lauth G. W. , Heubeck B. G. , Mackowiak K. 
Published: May 2006

Background. Observation studies of students with attention‐deficit hyperactivity disorder (ADHD) problems in natural classroom situations are costly and relatively rare.Aims. The study enquired how teacher ratings are anchored in actual student classroom behaviours, and how the behaviour of children with ADHD problems differs from their classmates. The authors attempted to broaden the usual focus on disruptive and inattentive behaviours to elucidate the role of various on‐task behaviours, as well as considering differences between classroom contexts.Sample. DSM‐III‐R criteria were used in conjunction with a teacher rating scale to select a sample of 55 students with ADHD problems, and 55 matched controls from a population of 569 primary school students.Method. Students were observed in their natural classrooms using the Munich Observation of Attention Inventory (MAI; Helmke, 1988). Correlations between teacher reports and observation codes were computed, and systematic differences between students with ADHD problems and controls in different classroom contexts were examined using a generalized linear mixed model (GLMM).Results. Global teacher reports showed moderate to strong correlations with observed student behaviours. Expected on‐task behaviour demonstrated the strongest relationship (r >−.70) with teacher reports. As hypothesized, the children with ADHD were more disruptive and inattentive than their matched peers. They were also less often inconspicuous on‐task as expected by their teachers. However, their behaviour was assigned to two other on‐task categories more often than their peers, and this raised their total on‐task behaviour to over 66%. Situational differences were found for all codes as well, which mostly affected all students in a similar way, not just students with ADHD.Conclusions. ADHD related behaviours are pervasive across the classroom situations coded. Teachers appear to distinguish between desirable and undesirable on‐task behaviours. Nevertheless, assisting students with ADHD problems requires shaping both. Future studies need to include more differentiated codes for various types of on‐task behaviours and also need to code the lesson context concurrently.
Teachers' and students' verbal behaviours during cooperative and small‐group learning
Authors: Gillies Robyn M. 
Published: May 2006

Background. Teachers play a critical role in promoting interactions between students and engaging them in the learning process. This study builds on a study by Hertz‐Lazarowitz and Shachar (1990) who found that during cooperative learning teachers' verbal behaviours were more helpful to and encouraging of their students' efforts while during whole‐class instruction, their verbal behaviours tended to be more authoritarian, rigid, and impersonal.Aim. This study seeks to determine if teachers who implement cooperative learning engage in more facilitative learning interactions with their students than teachers who implement group work only. The study also seeks to determine if students in the cooperative groups model their teachers' behaviours and engage in more positive helping interactions with each other than their peers in the group work groups.Samples. The study involved 26 teachers and 303 students in Grades 8 to10 from 4 large high schools in Brisbane, Australia.Methods. All teachers agreed to establish cooperative, small‐group activities in their classrooms for a unit of work (4 to 6 weeks) once a term for 3 school terms. The teachers were audiotaped twice during these lessons and samples of the students' language, as they worked in their groups, were also collected at the same time.Results. The results show that teachers who implement cooperative learning in their classrooms engage in more mediated‐learning interactions and make fewer disciplinary comments than teachers who implement group work only. Furthermore, the students model many of these interactions in their groups.Conclusions. The study shows that when teachers implement cooperative learning, their verbal behaviour is affected by the organizational structure of the classroom.
Reading errors in first‐ and second‐grade readers of a shallow orthography: Evidence from Spanish
Authors: Goikoetxea Edurne 
Published: May 2006

Background. Studies focusing on reading errors can help to understand how children learn to read and to structure key components of reading instruction. However, no prior studies have examined which letters might be a greater source of difficulty for beginning readers in Spanish.Aims. First, to examine the pattern of reading errors in beginning readers in a shallow orthography like Spanish with a particular focus on both the context‐dependant (c, g, r) and the visual similar (b, d, g, p, q) consonants. (The dual‐route cascade model is used as a theoretical framework for predictions.) Second, to examine the effect of visual similarity on orientation reversals, using upper and lower case letters.Sample. Ninety Spanish‐speaking children (45 in Grade 1 and 45 in Grade 2) participated in the study.Method. Children were required to read aloud both words and non‐words. Seven categories of errors were examined. To clarify the influence of visual similarity of easily confused consonants (b, d), upper and lower case letters were used.Results. We found that most reading errors (as a function of opportunity) were due to context‐dependant consonants (c, g, r), and a small proportion were due to the remaining consonants, or even the visually‐similar consonants. Further, visual similarity of reversible letters had a significant effect on orientation reversals. Finally, there was a significant influence of factors such as syllable frequency on the number of word errors.Conclusions. The implications of these findings for early reading instruction and future research are discussed.
Parallel Changes in Global Protein Profiles During Long-Term Experimental Evolution in Escherichia coli
Authors: Pelosi Ludovic , Kühn Lauriane , Guetta Dorian , Garin Jérôme , Geiselmann Johannes , Lenski Richard E , Schneider Dominique 
Published: May 2006

Abstract
Twelve populations of Escherichia coli evolved in and adapted to a glucose-limited environment from a common ancestor. We used two-dimensional protein electrophoresis to compare two evolved clones, isolated from independently derived populations after 20,000 generations. Exceptional parallelism was detected. We compared the observed changes in protein expression profiles with previously characterized global transcription profiles of the same clones; this is the first time such a comparison has been made in an evolutionary context where these changes are often quite subtle. The two methodologies exhibited some remarkable similarities that highlighted two different levels of parallel regulatory changes that were beneficial during the evolution experiment. First, at the higher level, both methods revealed extensive parallel changes in the same global regulatory network, reflecting the involvement of beneficial mutations in genes that control the ppGpp regulon. Second, both methods detected expression changes of identical gene sets that reflected parallel changes at a lower level of gene regulation. The protein profiles led to the discovery of beneficial mutations affecting the malT gene, with strong genetic parallelism across independently evolved populations. Functional and evolutionary analyses of these mutations revealed parallel phenotypic decreases in the maltose regulon expression and a high level of polymorphism at this locus in the evolved populations.
Signatures of Demographic History and Natural Selection in the Human Major Histocompatibility Complex Loci
Authors: Meyer Diogo , Single Richard M , Mack Steven J , Erlich Henry A , Thomson Glenys 
Published: May 2006

AbstractMany lines of evidence show that several HLA loci have experienced balancing selection. However, distinguishing among demographic and selective explanations for patterns of variation observed with HLA genes remains a challenge. In this study we address this issue using data from a diverse set of human populations at six classical HLA loci and, employing a comparative genomics approach, contrast results for HLA loci to those for non-HLA markers. Using a variety of analytic methods, we confirm and extend evidence for selection acting on several HLA loci. We find that allele frequency distributions for four of the six HLA loci deviate from neutral expectations and show that this is unlikely to be explained solely by demographic factors. Other features of HLA variation are explained in part by demographic history, including decreased heterozygosity and increased LD for populations at greater distances from Africa and a similar apportionment of genetic variation for HLA loci compared to putatively neutral non-HLA loci. On the basis of contrasts among different HLA loci and between HLA and non-HLA loci, we conclude that HLA loci bear detectable signatures of both natural selection and demographic history.
Functional Implication of an Arg307Gly Substitution in Corticosteroid-Binding Globulin, a Candidate Gene for a Quantitative Trait Locus Associated With Cortisol Variability and Obesity in Pig
Authors: Guyonnet-Dupérat Véronique , Geverink Nicoline , Plastow Graham S , Evans Gary , Ousova Olga , Croisetière Christian , Foury Aline , Richard Elodie , Mormède Pierre , Moisan Marie-Pierre 
Published: May 2006

Abstract
We previously reported that corticosteroid-binding globulin gene (Cbg) may be the causal gene of a quantitative trait locus associated with cortisol levels, fat deposition, and muscle content in a pig intercross. Sequence analysis of parental animals allowed us to identify four amino-acid substitutions. Here we have examined if any of these single amino acid substitutions could be responsible for the difference in CBG binding and affinity for cortisol between the parental breeds, using in vitro assays of Cbg variants after transfection of mammalian cells. Additionally, the Cbg coding region was analyzed in samples from a synthetic pig line to study association between polymorphism and CBG biochemical properties, carcass composition, and meat quality. Both in vitro transfection assays and the association studies suggest a role of the Arg307Gly mutation in increasing CBG capacity (by &gt;70%) and decreasing CBG affinity for cortisol (by 30%). The Ile265Val substitution may also have an effect on decreasing CBG affinity for cortisol by 25%. The mutations Ser15Ile and Thr257Met do not seem to have an effect on CBG parameters. The Arg307Gly substitution was the only mutation associated with a parameter of meat quality and no mutation was linked to carcass composition.
Parent-of-Origin Effects on mRNA Expression in Drosophila melanogaster Not Caused by Genomic Imprinting
Authors: Wittkopp Patricia J , Haerum Belinda K , Clark Andrew G 
Published: May 2006

Abstract
Parent-of-origin effects create differences in gene expression among genetically identical individuals. Using measurements of allele-specific expression, we demonstrate that previously reported parent-of-origin effects on standing mRNA levels in Drosophila melanogaster are not attributable to genomic imprinting. Offspring from reciprocal crosses exhibit differences in total expression without differences in allelic expression, indicating that other types of maternal and/or paternal effects alter expression.
High-Resolution Mapping of Quantitative Trait Loci Affecting Increased Life Span in Drosophila melanogaster
Authors: Wilson Rhonda H , Morgan Theodore J , Mackay Trudy F C 
Published: May 2006

Abstract
Limited life span and senescence are near-universal characteristics of eukaryotic organisms, controlled by many interacting quantitative trait loci (QTL) with individually small effects, whose expression is sensitive to the environment. Analyses of mutations in model organisms have shown that genes affecting stress resistance and metabolism affect life span across diverse taxa. However, there is considerable segregating variation for life span in nature, and relatively little is known about the genetic basis of this variation. Replicated lines of Drosophila that have evolved increased longevity as a correlated response to selection for postponed senescence are valuable resources for identifying QTL affecting naturally occurring variation in life span. Here, we used deficiency complementation mapping to identify at least 11 QTL on chromosome 3 that affect variation in life span between five old (O) lines selected for postponed senescence and their five base (B) population control lines. Most QTL were sex specific, and all but one affected multiple O lines. The latter observation is consistent with alleles at intermediate frequency in the base population contributing to the response to selection for postponed senescence. The QTL were mapped with high resolution and contained from 12 to 170 positional candidate genes.
Analysis of the Proteins Involved in thein VivoRepair of Base–Base Mismatches and Four-Base Loops Formed During Meiotic Recombination in the YeastSaccharomyces cerevisiae
Authors: Stone Jana E , Petes Thomas D 
Published: May 2006

AbstractDNA mismatches are generated when heteroduplexes formed during recombination involve DNA strands that are not completely complementary. We used tetrad analysis in Saccharomyces cerevisiae to examine the meiotic repair of a base–base mismatch and a four-base loop in a wild-type strain and in strains with mutations in genes implicated in DNA mismatch repair. Efficient repair of the base–base mismatch required Msh2p, Msh6p, Mlh1p, and Pms1p, but not Msh3p, Msh4p, Msh5p, Mlh2p, Mlh3p, Exo1p, Rad1p, Rad27p, or the DNA proofreading exonuclease of DNA polymerase δ. Efficient repair of the four-base loop required Msh2p, Msh3p, Mlh1p, and Pms1p, but not Msh4p, Msh5p, Msh6p, Mlh2p, Mlh3p, Exo1p, Rad1p, Rad27p, or the proofreading exonuclease of DNA polymerase δ. We find evidence that a novel Mlh1p-independent complex competes with an Mlhp-dependent complex for the repair of a four-base loop; repair of the four-base loop was affected by loss of the Mlh3p, and the repair defect of the mlh1 and pms1 strains was significantly smaller than that observed in the msh2 strain. We also found that the frequency and position of local double-strand DNA breaks affect the ratio of mismatch repair events that lead to gene conversion vs. restoration of Mendelian segregation.
A Clarification of the Hardy–Weinberg Law
Authors: Stark Alan E 
Published: May 2006

Abstract
C. C. Li showed that Hardy–Weinberg proportions (HWP) can be maintained in a large population by nonrandom mating as well as random mating. In particular he gave the mating matrix for the symmetric case in the most general form possible. Thus Li showed that, once HWP are attained, the same proportions can be maintained by what he called pseudorandom mating. This article shows that, starting from any genotypic distribution at a single locus with two alleles, the same in each sex, HWP can be reached in one round of nonrandom mating with no change in allele frequency. In the model that demonstrates this fact, random mating is represented by a single point in a continuum of nonrandom possibilities.
A Novel Approach for Characterizing Expression Levels of Genes Duplicated by Polyploidy
Authors: Udall Joshua A , Swanson Jordan M , Nettleton Dan , Percifield Ryan J , Wendel Jonathan F 
Published: May 2006

AbstractStudying gene expression in polyploids is complicated by genomewide gene duplication and the problem of distinguishing transcript pools derived from each of the two homeologous genomes such as the A- and D-genomes of allotetraploid Gossypium. Short oligonucleotide probes designed to specifically target several hundred homeologous gene pairs of Gossypium were printed on custom NimbleGen microarrays. These results demonstrate that relative expression levels of homeologous genes may be measured by microarrays and that deviation from equal expression levels of homeologous loci may be common in the allotetraploid nucleus of Gossypium.
The Hill–Robertson Effect and the Evolution of Recombination
Authors: Roze Denis , Barton Nick H 
Published: May 2006

Abstract
In finite populations, genetic drift generates interference between selected loci, causing advantageous alleles to be found more often on different chromosomes than on the same chromosome, which reduces the rate of adaptation. This “Hill–Robertson effect” generates indirect selection to increase recombination rates. We present a new method to quantify the strength of this selection. Our model represents a new beneficial allele (A) entering a population as a single copy, while another beneficial allele (B) is sweeping at another locus. A third locus affects the recombination rate between selected loci. Using a branching process model, we calculate the probability distribution of the number of copies of A on the different genetic backgrounds, after it is established but while it is still rare. Then, we use a deterministic model to express the change in frequency of the recombination modifier, due to hitchhiking, as A goes to fixation. We show that this method can give good estimates of selection for recombination. Moreover, it shows that recombination is selected through two different effects: it increases the fixation probability of new alleles, and it accelerates selective sweeps. The relative importance of these two effects depends on the relative times of occurrence of the beneficial alleles.
Transcriptionally Silenced Transgenes in Maize Are Activated by Three Mutations Defective in Paramutation
Authors: McGinnis Karen M , Springer Catherine , Lin Yan , Carey Charles C , Chandler Vicki 
Published: May 2006

Abstract
Plants with mutations in one of three maize genes, mop1, rmr1, and rmr2, are defective in paramutation, an allele-specific interaction that leads to meiotically heritable chromatin changes. Experiments reported here demonstrate that these genes are required to maintain the transcriptional silencing of two different transgenes, suggesting that paramutation and transcriptional silencing of transgenes share mechanisms. We hypothesize that the transgenes are silenced through an RNA-directed chromatin mechanism, because mop1 encodes an RNA-dependent RNA polymerase. In all the mutants, DNA methylation was reduced in the active transgenes relative to the silent transgenes at all of the CNG sites monitored within the transgene promoter. However, asymmetrical methylation persisted at one site within the reactivated transgene in the rmr1-1 mutant. With that one mutant, rmr1-1, the transgene was efficiently resilenced upon outcrossing to reintroduce the wild-type protein. In contrast, with the mop1-1 and rmr2-1 mutants, the transgene remained active in a subset of progeny even after the wild-type proteins were reintroduced by outcrossing. Interestingly, this immunity to silencing increased as the generations progressed, consistent with a heritable chromatin state being formed at the transgene in plants carrying the mop1-1 and rmr2-1 mutations that becomes more resistant to silencing in subsequent generations.