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  2. Tetrad (meiosis) - Wikipedia

    en.wikipedia.org/wiki/Tetrad_(meiosis)

    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 ...

  3. List of medical triads, tetrads, and pentads - Wikipedia

    en.wikipedia.org/wiki/List_of_medical_triads...

    The appearance of all three signs conjoined together in another patient, points to that the patient has the same medical condition, or diagnosis. A medical tetrad is a group of four, while a pentad is a group of five.

  4. Bivalent (genetics) - Wikipedia

    en.wikipedia.org/wiki/Bivalent_(genetics)

    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.

  5. Chiasma (genetics) - Wikipedia

    en.wikipedia.org/wiki/Chiasma_(genetics)

    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 ...

  6. Bacterial cellular morphologies - Wikipedia

    en.wikipedia.org/wiki/Bacterial_cellular...

    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.

  7. Tetralogy of Fallot - Wikipedia

    en.wikipedia.org/wiki/Tetralogy_of_Fallot

    The abnormal "coeur-en-sabot" (boot-like) appearance of a heart with tetralogy of Fallot is classically visible via chest X-ray, although most infants with tetralogy may not show this finding. [49] The boot like shape is due to the right ventricular hypertrophy present in TOF.

  8. Tetrachromacy - Wikipedia

    en.wikipedia.org/wiki/Tetrachromacy

    The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.

  9. Chromosomal crossover - Wikipedia

    en.wikipedia.org/wiki/Chromosomal_crossover

    The grasshopper Melanoplus femur-rubrum was exposed to an acute dose of X-rays during each individual stage of meiosis, and chiasma frequency was measured. [23] Irradiation during the leptotene - zygotene stages of meiosis (that is, prior to the pachytene period in which crossover recombination occurs) was found to increase subsequent chiasma ...