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The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, Chlamydomonas or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and undergo meiosis. The meiotic products, spores, remain packaged in the parental cell body to produce ...
The structure, visible by microscopy, is called a bivalent. An intricate molecular machinery is at the core of gene expression regulation in every cell. During the initial stages of organismal development, the coordinated activation of diverse transcriptional programs is crucial and must be carefully executed to shape every organ and tissue.
Tetrad Disease Tetralogy of Fallot: pulmonary stenosis, ventricular septal defect, right ventricular hypertrophy, overriding aorta: Tetralogy of Fallot Ménière's disease: vertigo, tinnitus, fluctuating low frequency hearing loss, aural fullness: Ménière's disease zoonotic tetrad: scrub typhus, chiggers, rodents and birds, scrub vegetation
When each tetrad, which is composed of two pairs of sister chromatids, begins to split, the only points of contact are at the chiasmata. The chiasmata become visible during the diplotene stage of prophase I of meiosis, but the actual "crossing-overs" of genetic material are thought to occur during the previous pachytene stage. Sister chromatids ...
But, there are also other morphologies such as helically twisted cylinders (example Spirochetes), cylinders curved in one plane (selenomonads) and unusual morphologies (the square, flat box-shaped cells of the Archaean genus Haloquadratum). Other arrangements include pairs, tetrads, clusters, chains and palisades.
The tetractys. The tetractys (Greek: τετρακτύς), or tetrad, [1] or the tetractys of the decad [2] is a triangular figure consisting of ten points arranged in four rows: one, two, three, and four points in each row, which is the geometrical representation of the fourth triangular number.
In this book, a frame field is called a tetrad (not to be confused with the now standard term NP tetrad used in the Newman–Penrose formalism). See Section 98. De Felice, F.; Clarke, C. J. (1992). Relativity on Curved Manifolds. Cambridge: Cambridge University Press. ISBN 0-521-42908-0. See Chapter 4 for frames and coframes. If you ever need ...
We first need to introduce the notion of tetrads. A tetrad is an orthonormal vector basis in terms of which the space-time metric looks locally flat, = where = (,,,) is the Minkowski metric. The tetrads encode the information about the space-time metric and will be taken as one of the independent variables in the action principle.