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Meiosis

Meiosis. Objective: 3.04 Cellular Division to produce Haploid Gametes. Let’s Refresh…. Diploid means each chromosome has an identical match in the cell. Our somatic cells are diploid. (2n) So we have 23 PAIRS of chromosomes, or 46 total .

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Meiosis

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  1. Meiosis Objective: 3.04 Cellular Division to produce Haploid Gametes

  2. Let’s Refresh… • Diploid means each chromosome has an identical match in the cell. • Our somatic cells are diploid. (2n) • So we have 23 PAIRS of chromosomes, or 46 total. • Haploidmeans we have one set of individual chromosomes, no pairs. • Our gametes are haploid (n) • So we have 23 different chromosomes

  3. Mitosis vs. Meiosis • Mitosis is reproduction of asexual cells, while Meiosis is reproduction of sex cells. • Our somatic cells do mitosis to make more of themselves, and it involves one cellular division. • Our gametes do a process similar to mitosis, called meiosis, except it involves TWO cellular division

  4. So explain Meiosis to me… • Just like in mitosis, during meiosis, the parent cell makes copies of all the DNA (chromosomes) before the first split.  • One difference is that pieces of the chromosomes break off and reattach to each other (they exchange their DNA).  This is known as crossing over and is important in the variation of offspring. (Why siblings do not look identical)

  5. Again, just like mitosis, the parent splits into two daughter cells, each with their own set of DNA, except this time they are NOT identical because of the crossing over in the previous replication phase.

  6. You now have two diploid daughter cells with DIFFERENT DNA that are going to go through their own division, except this time they do NOT make copies of their chromosomes before dividing.  This will half the number of chromosomes that the NEW daughter cells will receive (46 --> 23). • Therefore, your end result is 4 haploid cells. Meiosis

  7. Remember, MiTosis = MainTains the number of chromosomes (46 is your beginning number, 46 is your ending number) • while MeiOsis = LOwers the number of chromosomes (46 is your beginning number, 23 is your ending number)

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