Meiosis. How meiosis occurs. 4.0 / 5 based on 5 ratings ? BiologyDNA and inheritanceGCSEAll boards Created by: NickCreated on: 26-02-12 20:41 Why? - Gametes have half the usual number of chromosomes (23). They are haploid (one copy of each chromosome) - Gametes are sex cells (Ova = female, Sperm = male). - The two gametes combine during reproduction to form a new cell. (46 chromosomes). 1 of 6 How? - Before the cell divides it duplicates it's DNA. (as with Mitosis) - In the first of two divisions in meiosis the chromosome pairs line up in the centre of the cell. 2 of 6 How? - They're pulled apart so each new cell only has one copy of each chromosome. - Each new cell is made up of chromosomes from both the mother and father. 3 of 6 How? - Each new cell has a mixture of chromosomes from the mother and the father. - This provides variation in the offspring. - Huge advantage of sexual reproduction over asexual. 4 of 6 How? - In the second division the chromosomes line up again in the centre of the cell. - The arms of the chromosomes are pulled apart (like Mitosis). 5 of 6 How? - You get 4 gametes. - They have a single set of chromosomes each (23). 6 of 6
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