366 research outputs found
Ploidy and genome composition of Musa germplasm at the International Institute of Tropical Agriculture (IITA)
Musa spp (bananas and plantains) constitute a hybrid-polyploid complex and are classified according to different genome compositions such as AA, BB, AB, AAA, AAB, ABB, AAAA, ABBB, AAAB and AABB. Knowledge of ploidy and exact genome compositions of the parental material is essential forMusa breeding. This study determined the ploidy levels and genome composition of the Musa germplasm collection, constituting over 300 accessions, at the International Institute of Tropical Agriculture in Nigeria and Uganda. Flow cytometric analysis of nuclear DNA content was used toestimate ploidy levels, while genome composition was ascertained with RAPD markers that are specific for the A and B genomes of Musa. It was determined that at least 8% of the plants in the germplasmcollection were miss-classified in terms of ploidy and/or genome composition. The cultivars 'Pisang awak', 'Foulah 4' and 'Nzizi', previously classified as triploids, were found to be tetraploids by flowcytometry and conventional root tip chromosome counts. Similarly, cultivars that were previously classified as diploids including ‘Too’, and ‘Toowoolee’ were found to be triploids in our analysis. Ploidy and genome classification in Musa was generally determined from morphological characteristics. While our study showed that such a system is not always reliable, it was interesting to find that none of the plantains in the germplasm collection were miss-classified with regards to both ploidy and genome composition
Genomics goes chromosomal to explore the wheat genome
OBJECTIVES: The implant design and surface modification are independent conditions that can alter the implant bone response. The objective of this study is to compare the bone response to roughened tapered and cylindrical screw-type implants with and without hydroxyapatite (HA) surface coating in the femoral trabecular bone of rabbits. MATERIAL AND METHOD: Thirty-two implants (8 x 3.5 mm) consisting of four different types (eight implants in each group), that is, tapered implants, cylindrical implants, HA-coated tapered implants, and HA-coated cylindrical implants were installed in the femoral condyle of 16 rabbits. After 8 weeks of healing, the femoral condyles were retrieved and studied histologically. The bone-to-implant contact percentage was assessed and analyzed statistically. Results : The histomorphometric analysis revealed that the bone-to-implant contact (BIC) values seemed to be higher for HA-coated tapered implants (65.62 +/- 13.02) followed by cylindrical non-coated implants. All four types of implants showed wide distribution of BIC with no statistical significance between different types of implants. CONCLUSION: It can be concluded that under the current experimental conditions, implant design and surface composition had little effect on the bone-to-implant interface
New Drosophila circadian clock mutants affecting temperature compensation induced by targeted mutagenesis of Timeless
Drosophila melanogaster has served as an excellent genetic model to decipher the
molecular basis of the circadian clock. Two key proteins, PERIOD (PER) and TIMELESS
(TIM), are particularly well explored and a number of various arrhythmic, slow, and fast
clock mutants have been identified in classical genetic screens. Interestingly, the free
running period (tau, t) is influenced by temperature in some of these mutants, whereas
t is temperature-independent in other mutant lines as in wild-type flies. This, so-called
\u201ctemperature compensation\u201d ability is compromised in the mutant timeless allele \u201critsu\u201d
(tim rit), and, as we show here, also in the tim blind allele, mapping to the same region of
TIM. To test if this region of TIM is indeed important for temperature compensation, we
generated a collection of new mutants and mapped functional protein domains involved
in the regulation of t and in general clock function. We developed a protocol for targeted
mutagenesis of specific gene regions utilizing the CRISPR/Cas9 technology, followed by
behavioral screening. In this pilot study, we identified 20 new timeless mutant alleles with
various impairments of temperature compensation. Molecular characterization revealed
that the mutations included short in-frame insertions, deletions, or substitutions of a
few amino acids resulting from the non-homologous end joining repair process. Our
protocol is a fast and cost-efficient systematic approach for functional analysis of
protein-coding genes and promoter analysis in vivo. Interestingly, several mutations with
a strong temperatur
Second-generation chromosome-specific BAC resources in wheat
In the societal and scientific discussions about the support for democracy and gender equality in the Arab Middle East, this study engages the triangular theory, which predicts that Islamic orientations influence gender equality attitudes and democracy negatively, and attitudes towards gender equality are also expected to lead to more democratic support, partly channelling the influence of Islam. This theory was tested on Arab Barometer data for seven countries, including three different dimensions of Islamic-religious identity: affiliation, piety, and political-Islamist attitudes. The analyses roughly back the triangular model, but for democratic support only the Islamist values seem important, partly working through economic gender equality attitudes. Attitudes towards women’s position in politics and education seem unrelated to democratic support. In addition, this study applies the gender and postcolonial concept of ‘othering’ to the triangular model. Theoretically it predicts that in the current neo-colonial era, anti-Western feelings might create more Islamic and less democracy and gender equal attitudes simultaneously, making Islam’s impact partly spurious. Empirically, this is modestly supported for the Islamist-democracy link only. However, anti-Western feelings do relate to gender equality, democratic support, and religious attitudes, and deserves more attention when studying democracy and gender equality in the Arab Middle East
Slowly rotating voids in cosmology
We consider a spacetime consisting of an empty void separated from an almost
Friedmann-Lema\^\i tre-Robertson-Walker (FLRW) dust universe by a spherically
symmetric, slowly rotating shell which is comoving with the cosmic dust. We
treat in a unified manner all types of the FLRW universes. The metric is
expressed in terms of a constant characterizing the angular momentum of the
shell, and parametrized by the comoving radius of the shell. Treating the
rotation as a first order perturbation, we compute the dragging of inertial
frames as well as the apparent motion of distant stars within the void.
Finally, we discuss, in terms of in principle measurable quantities, 'Machian'
features of the model.Comment: 21 pages, 5 figures, REVTex, accepted for publication in
Class.Quant.Gravit
Gravity on de-Sitter 3-Brane, Induced Einstein-Hilbert Term and Massless Gravitons
We study the extensions of DGP model which are described by five-dimensional
Einstein gravity coupled covariantly to 3-brane with induced gravity term and
consider warped D=4 de Sitter background field solutions on the brane. The case
with included D=5 AdS cosmological term is also considered. Following
background field method we obtain the field equations described by the
Lagrangean terms bilinear in gravitational field. In such a linear field
approximation on curved dS background we calculate explicitly the
five-dimensional massive terms as well as the mass-like ones on the brane. We
investigate the eigenvalue problem of Schr\"{o}dinger-like equation in fifth
dimension for graviton masses and discuss the existence of massless as well as
massive graviton modes in the bulk and on the brane without and with induced
gravity.Comment: LaTeX 26 pages, the version which appears in Class. Quant. Gra
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