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The four main steps of meiosis II are: prophase II, metaphase II, anaphase II, and telophase II. In prophase II, we see the disappearance of the nucleoli and the nuclear envelope again as well as the shortening and thickening of the chromatids. Centrosomes move to the polar regions and arrange spindle fibers for the second meiotic division.
The cumulus-oocyte complex contains layers of tightly packed cumulus cells surrounding the oocyte in the Graafian follicle. The oocyte is arrested in Meiosis II at the stage of metaphase II at the diplotene stage and is considered a secondary oocyte. Before ovulation, the cumulus complex goes through a structural change known as cumulus ...
Metaphase (from Ancient Greek μετα- beyond, above, transcending and from Ancient Greek φάσις (phásis) 'appearance') is a stage of mitosis in the eukaryotic cell cycle in which chromosomes are at their second-most condensed and coiled stage (they are at their most condensed in anaphase). [1]
During G 2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase can be either mitosis or meiosis depending on the type of cell. Germ cells, or gametes, undergo meiosis, while somatic cells will undergo mitosis. After the cell proceeds successfully through the M phase, it may ...
Original – A diagram showing the stages of meiosis, a specialized type of cell division that reduces the chromosome number by half. Reason Very encyclopedic, attractive Articles in which this image appears Meiosis FP category for this image Wikipedia:Featured pictures/Diagrams, drawings, and maps/Diagrams Creator Ali Zifan
Due to this genetic recombination, the offspring have a different set of alleles and genes than their parents do. In the diagram, genes B and b are crossed over with each other, making the resulting recombinants after meiosis Ab, AB, ab, and aB. Thomas Hunt Morgan's illustration of crossing over (1916) A double crossing over
Until the preovulatory stage, the follicle contains a primary oocyte that is arrested in prophase of meiosis I. During the late preovulatory stage, the oocyte continues meiosis and becomes a secondary oocyte, arrested in metaphase II. (a) The maturation of a follicle is shown in a clockwise direction proceeding from the primordial follicles.
Meiosis II follows at once but will be arrested in the metaphase and will so remain until fertilization. The spindle apparatus of the second meiotic division appears at the time of ovulation. If no fertilization occurs, the oocyte will degenerate between 12 and 24 hours after ovulation. [18] Approximately 1–2% of ovulations release more than ...