1,720,954 research outputs found
Cytogenetic analyses applied to the identification of haploids and doubled-haploids in corn
No full textDuplo-haploides (DH) são genótipos resultantes de indução à haploidia e posterior duplicação genômica. Essa técnica é de grande interesse agronômico, pois permite a redução do tempo de obtenção de endogâmicos e o alcance de 100% da homozigosidade dos genótipos, o que aprimora e agiliza o processo de obtenção de linhagens e híbridos. Entretanto, as metodologias de obtenção e identificação dos haploides (H) e DH nem sempre são eficientes. Deste modo, este estudo examinou 8 possíveis genótipos de milho H e DH: 1700346, 1700347, 1700348, 1700349, 1700350, 1700351, 1700352, 1700353, com o intuito de confirmar ou seus níveis de ploidia, bem como a metodologia de obtenção e identificação dos H e DH, e verificar a estabilidade meiótica do material DH. Para a contagem dos cromossomos e análise dos H, lâminas foram preparadas utilizando a técnica squash, com corante carmim acético 2% para as análises mitóticas e solução de Alexander para VP. Dos 8 H analisados, 7 apresentaram 100% das metáfases com 20 cromossomos, confirmando seu status de H, e 1, H1700349, apresentou metáfases com 10 cromossomos e 90% com 20, configurando-se como H e diploides. As análises meióticas dos DH falharam em 100% das células em ambas as fases da divisão meiótica, resultando em material não viável.Double haploids (DH) are genotypes resulting from haploid induction and subsequent genomic duplication. This technique is of great agronomic interest, as it allows for a reduction in the time to obtain inbreds and the achievement of 100% of the homozygosity of the genotypes, which improves and speeds up the process of obtaining inbred lines and hybrids. However, the methodologies for obtaining and identifying haploids (H) and DH are not always efficient. Thus, this study examined 8 possible genotypes of corn H and DH: 1700345, 1700346, 1700347, 1700348, 1700349, 1700350, 1700351, 1700352, in order to confirm their ploidy levels, validating the methodology for obtaining and identifying the H and DH, and verify the meiotic stability of the possible DH material. To count the chromosome number of H, slides were prepared using root tips with mitotic blockage made by a 19:1 solution of 8-hydroxyquinone 300ppm and cycloheximide 23ppm and staining via the Feulgen method. To verify ploidy, meiotic phase regularity, recombination index (RI), meiotic index (MI) and pollen viability (VP) of DH, slides were prepared using the squash technique, stained using acetic carmine 2% for meiotic analysis and Alexander’s solution for VP. Of the 8 H analyzed, 7 presented 100% of the metaphases with 20 chromosomes, configuring themselves as diploids and 1, H1700349, presented 10% of the metaphases with 10 chromosomes and 90% with 20, configuring themselves as H and diploids. Meiotic analyses showed that all 8 DH had 10 bivalents, proving that they remain diploid and that chromosome duplication failed in all genotypes. The averages for the values obtained in IR, IM and VP, for all genotypes, were, respectively, 28.39, 95.62% and 76.05%. Meiotic abnormalities met the standards for corn. These results reveal that only in H1700349 the obtaining of H showed efficiency, that the duplication of genotypes was not efficient and that all genotypes had medium and high indices of meiotic regularity, IM, IR and VP. Therefore, the protocol for obtaining H and DH was not efficient and the stress caused by it did not significantly affect the meiotic regularity of the analyzed genotypes.Conselho Nacional de Desenvolvimento Científico e Tecnológic
Inheritance, cytogenetics and phenotypes of a maize TB-9Sb translocation
No full textTB-9Sb, um rearranjo cromossômico do tipo B-A no milho, é uma translocação recíproca envolvendo os cromossomos 9 e B, formando os cromossomos B-9 e 9-B. Esses rearranjos são fundamentais para estudos genéticos no milho, permitindo investigações sobre dosagens gênicas, dominância, codominância, herança e transmissão cromossômica dos cromossomos Bs, bem como o comportamento da cromatina mista entre os cromossomos do complemento A e do cromossomo B. A validação e a caracterização desses cromossomos são essenciais para garantir a precisão dos dados fenotípicos e compreender os fenótipos gerados e sua herança. No entanto, apesar de mais de 75 anos de estudo, a translocação TB-9Sb ainda carece de uma caracterização cromossômica por FISH (Hibridização molecular in situ fluorescente). Assim, este estudo utilizou três linhagens de milho diferentes: as linhagens B73 e B73+B como controles, e a linhagem TB-9Sb com o marcador genético C (colored aleurone1) cromossomo B-9, visando descrever citogeneticamente a estrutura dos cromossomos envolvidos na translocação TB-9Sb e analisar sua herança e fenótipos ao longo das progênies. Para isso, as técnicas empregadas incluíram a coloração pelo método de Feulgen para a contagem do número de cromossomos; a FISH para a identificação de cromossomos com regiões com sequencias especídicas de centrômeros, cromossomos B e knobs, utilizando as sondas CentC, B-Specific K180 em cromossomos mitóticos e meióticos; e a realização de duas repetições de plantio para comparar o fenótipo da prole das linhagens. A linhagem TB-9Sb utilizada neste estudo apresentou segregação para dois fenótipos: semente roxa TB-9Sb-C e semente amarela/incolor TB-9Sb-c, tratados como populações distintas. A caracterização cromossômica revelou que TB9Sb-c e TB-9Sb-C possuem cromossomos B-9 distintos, sendo TB-9Sb-c caracterizado pela ausência do marcador C e TB-9Sb-C por uma deleção no segmento do knobs heterocromático K9S. Apesar da deleção em TB-9Sb-C, o cromossomo B-9 demonstrou não-disjunção e fertilização preferencial. A análise fenotípica e correlacional entre os genótipos B73 e TB-9Sb-c e TB-9Sb-C revelou semelhanças e diferenças notáveis, especialmente nas características de altura da planta, altura de inserção da espiga e comprimento do pendão, destacando o desempenho superior do genótipo TB-9Sb-c em relação às demais variantes.TB-9Sb, a B-A chromosomal rearrangement in maize, is a reciprocal translocation involving chromosomes 9 and B, forming the B-9 and 9-B chromosomes. These rearrangements are crucial for genetic studies in maize, allowing investigations into gene dosage, dominance, codominance, inheritance, and chromosomal transmission of the B chromosomes, as well as the behavior of mixed chromatin between the A complement chromosomes and chromosome B. Validation and characterization of these chromosomes are essential to ensure the accuracy of phenotypic data and to understand the generated phenotypes and their inheritance. However, despite over 75 years of study, the TB-9Sb translocation still lacks chromosomal characterization via FISH (Fluorescence in situ hybridization). Thus, this study used three different maize lines: the B73 and B73+B lines as controls, and the TB-9Sb line with the C genetic marker (colored aleurone1) on chromosome B-9, aiming to cytogenetically describe the structure of the chromosomes involved in the TB-9Sb translocation and analyze their inheritance and phenotypes throughout the progenies. For this, the techniques used included staining using the Feulgen method for chromosome counting; FISH to identify chromosomes with specific centromere, B chromosome, and knob sequences using probes such as CentC, B-Specific, and K180 on mitotic and meiotic chromosomes; and carrying out two rounds of planting to compare the phenotypes of the lines. The TB-9Sb line used in this study segregated into two phenotypes: TB-9Sb-C purple seeds and TB-9Sb-c yellow/colorless seeds, treated as distinct populations. Chromosomal characterization revealed that TB-9Sb-c and TB-9Sb-C have distinct B-9 chromosomes, with TB-9Sb-c characterized by the absence of the C marker and TB-9Sb-C by a deletion in the K9S heterochromatic knob segment. Despite the deletion in TB-9Sb-C, the B-9 chromosome showed non-disjunction and preferential fertilization. Phenotypic and correlational analysis between B73 and TB-9Sb-c and TB-9Sb-C genotypes revealed notable similarities and differences, especially in plant height, ear insertion height, and tassel length, highlighting the superior performance of the TB-9Sb-c genotype compared to other variants
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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