Meiosis and Mitosis are cold! by Kayla Hageman https://padlet.com/onceuponakayla/28r5wu4zu1kh677g Made with good vibes en-us 2021-11-08 01:44:59 UTC 2021-11-22 03:35:45 UTC hello@padlet.com https://padlet.net/icons/png/1f61c.png onceuponakayla https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1900413075
  • Meiosis is a type of cell division reproduction that requires two cellular divisions that occur one after the other and result in four daughter cells. Meiosis is to thank for genetic individuality and the presence of gametes like sperm and eggs that pass along genetic information. Unlike Mitosis, the cell division of Meiosis occurs twice, which means that the phases need to be numbered 1 and 2.
  • The daughter cells that are created are haploid, which means that the number of chromosomes in the cell is divided in half from the parent cell. A human has 46 pairs of chromosomes, 23 from the mother and 23 from the father. The number of chromosomes in the cell is called the Ploidy Level. Before the phases of meiosis truly begin, the cell is in interphase. During interphase, which also occurs in mitosis, the cell is busy growing, replicating DNA, and participating in cell processes and functions.
  • There are four stages during each division of meiosis:
    • Phase 1 - Prophase I - before prophase can begin, the chromosomes have replicated and have formed sister chromatids, of which there are four (two chromosomes in each sister pair). The sisters are inside what is called a nuclear envelope which disintegrates and closes in on the chromatids. The chromatids begin a process called crossing over where non-sister chromatids form homologous pairs.
    • Phase 2 - Metaphase I - During metaphase, the chromosome pairs are moved to the middle of the cell in preparation for the spindle fibers to pull the pairs apart. The pairs are in a random order in the middle of the cell, and this is called independent assortment, or Mendel's Law of Independent Assortment.
    • Phase 3 - Anaphase I - The spindle fibers have attached to the homologous chromosomes and now begin the process of pulling the pairs apart. The sister chromatids are still holding on to each other and remain attached by the centromere.
    • Phase 4 - Telophase I - The homologous pairs are pulled to separate poles. In some organisms, the chromosomes expand or de-condense, and a brand new nuclear envelope forms around them. It is here that cytokinesis (the separation of the cytoplasmic parts of daughter cells) begins to form the nuclei of a new cell.
  • Meiosis II - The sister pairs of chromosomes that remain will be split apart resulting in new cells. 
    • Phase 1 - Prophase II - The chromosomes again condense to prepare them to be arranged. If the nuclear envelope had begun to reform, it is broken into vesicles. New spindle fibers are formed in preparation for the impending division.
    • Phase 2 - Metaphase II - The sister chromosomes are lined up in the middle of the cell and are at their most condensed state.
    • Phase 3 - Anaphase II - The sister chromosomes are pulled apart by the spindle fibers. They are then pulled toward opposite sides of the cell called poles, and here they will remain until the cell divides.
    • Phase 4 - Telophase II - The chromosomes arrive at their new poles and de-condense. New nuclear envelopes begin to form around the poles and their chromosomes. The new cells are haploid and only have one set of chromosomes.
    • (Fowler et al., 2021)
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  • Unlike Meiosis, mitosis only occurs with one cell division. This singular nuclear division results in two nuclei which live in two new cells. The mother and daughter cells have the same number of chromosomes, which is also called diploid.
  • Mitosis creates body cells like skin, finger nails, and all things that grow in the body. It is because the cells that are created through mitosis are identical to the mother that things are able to heal and grow. Just like in Meiosis, before the process of cell division begins, the cell that is going to duplicate begins the process of interphase. During interphase, the DNA inside the cell is duplicated.
    • Phase 1 - Prophase - The chromosomes are still in the nucleus, but they have begun to thicken and condense. Spindle fibers have begun to form.
    • Phase 2 - Metaphase - The nucleus has been broken down and the chromosomes are lined up in the middle of the cell. Spindle fibers are moving in and begin to attach to each chromatid. 
    • Phase 3 - Anaphase - The chromosome pairs are separated and the spindle fibers pull chromatids to either side of the cell. These are called the poles, and will eventually each be different cells. 
    • Phase 4 - Telophase - Now that the chromatids are at their new poles, new nuclear envelopes begin to form around them. Finally, cytokinesis occurs which completes the division of the cytoplasm and officially creates two new cells. 
    • (Fowler et al., 2021)
    ]]>     2021-11-19 19:26:04 UTC https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902808898     onceuponakayla https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902811613 2021-11-19 19:27:42 UTC https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902811613 onceuponakayla https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902814683 Fowler, S., Roush, R. & Wise, J. (2021, January 12). Concepts of biology. Open Stax College.

    Science Facts. (2020, October 13). Mitosis: Definition, stages, & purpose, with diagram. Science Facts. Retrieved November 19, 2021, from https://www.sciencefacts.net/mitosis.html.

    Waris, A. (2017). What is meiosis? Quora. Retrieved November 19, 2021, from https://www.quora.com/What-is-meiosis.  ]]>     2021-11-19 19:29:46 UTC https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902814683     onceuponakayla https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902965298 2021-11-19 21:35:01 UTC https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902965298 onceuponakayla https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902966670 2021-11-19 21:36:30 UTC https://padlet.com/onceuponakayla/28r5wu4zu1kh677g/wish/1902966670