![]() ![]() In order to prepare for the next division, prophase II condenses chromatin first into chromatids, and then more tightly into chromosomes. Prophase II begins immediately after cytokinesis – the splitting of the diploid gamete into two haploid daughter cells. A much less complex phase than prophase I, prophase II does not include the steps of leptotene, zygotene, pachytene, diplotene, and diakinesis but more resembles the simpler process of mitotic prophase in non-gamete (somatic) cell division. Prophase II prepares the cell for secondary meiotic division where two haploid cells eventually form four haploid cells, each containing half of the genetic information previously contained in the original, replicated diploid cell. As no DNA replication takes place in this second step of meiosis, the cell division process immediately begins. ![]() Meiosis II occurs in both daughter cells that were formed during meiosis I. However, centrosomes are not present in all cells. These are the condensing of chromatin into chromosomes, disintegration of the nuclear envelope, migration of centrosomes to either pole, and the reconstruction of the spindle apparatus. Also a nucleolus appears within each new nucleus and single stranded chromosomes uncoil into invisible strands of chromatin.During prophase II of meiosis II, four important steps occur. The spindle fibers begin to disappear, and a nuclear membrane forms around each set of chromosomes. One set of chromosomes is now at each pole of the cell. Telophase is the final stage in mitosis: the cell itself is ready to divide. The cell begins to stretch out as the opposite ends are pushed apart. Another group of microtubules, the non-kinetochore microtubules, do the opposite. The microtubules hold on to kinetochore and shorten in length. ![]() The kinetochore is attached to the centromere. Anaphaseĭuring anaphase, the sister chromatids split apart and move from the cell's equator (metaphase plate) to the poles of the cell. The chromosomes line up on the cell's equator, or center line, and are prepared for division. Both sister chromatids stay attached to each other at the centromere. Metaphaseĭuring metaphase, the sister chromatids are aligned by the pushing and pulling of the attached kinetochore microtubules, similar to a game of "tug of war". Long thin proteins reach across from opposite poles of the cell and attach to each kinetochore. A protein called a kinetochore forms at each centromere. Now there is no nucleus and the sister chromatids are free. Prometaphaseĭuring prometaphase, the nuclear envelope around the chromosomes breaks down. Spindle fibers begin to form a bridge between the ends of the cell. Pairs of centrioles move to opposite sides of the nucleus. Telophase: Reversal of prophase and prometaphase eventsĭuring prophase, chromosomes in the nucleus condense. The gametes are produced by a different division method called meiosis. The sperm and ova are gametes or sex cells. Mitosis happens in all types of dividing cells in the human body except with sperm and ova. Since the two chromatids are identical to each other, they are called sister chromatids. The chromosomes are now two chromatids joined at the centromere. At the beginning of mitosis the chromosomes wind up into visible objects that can be seen with a light microscope. The genetic information is in the DNA of the chromosomes. The chromosomes of a cell are copied to make two identical sets of chromosomes, and the cell nucleus divides into two identical nuclei.īefore mitosis, the cell creates an identical set of its own genetic information – this is called DNA replication. Mitosis is part of the cycle of cell division. pair of daughter-cells shortly after division dividing cells showing mitotic figures e. nuclei preparing for division (spireme-stage) c. ![]() Onion ( Allium) cells in different phases of the cell cycle enlarged 800 diameters. ![]()
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