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Meiosis is a critical cellular division process that produces haploid gametes, essential for sexual reproduction. Unlike mitosis, which results in two identical diploid cells, meiosis involves two rounds of division and introduces genetic variation through crossing over. During meiosis, a diploid parent cell duplicates its DNA, undergoes genetic recombination, and ultimately divides to create four diverse haploid cells, each with a unique set of chromosomes. This reduction from 46 chromosomes to 23 is vital for maintaining genetic diversity in offspring.
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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. • Haploidmeans we have one set of individual chromosomes, no pairs. • Our gametes are haploid (n) • So we have 23 different chromosomes
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
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)
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.
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
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)