I don’t understand the division of the chromosomes. The math just doesn’t add up.
Mitosis: Start with 46 chromosomes (2n). Replicate to become 92 chromosomes. Then divide to produce 46 (2n) chromosomes. Okay, makes sense.
Meiosis: Start with 46 (2n). Replicate to become 92 chromosomes. Then divide to become 2 cells with (1n). How? They THEN divide to become 4 cells with (1n) as well. How? How can they divide when they’re just (1n). Am I missing something?
In: Biology
So the “n” count is a bit weird and seems to be what’s throwing you off. N is not the total # of copies of each chromatid (which is sometimes called “c”). “N” is more correctly equal to the number of centromeres present –so one “X” chromosome is 1n, but a chromosome once broken into its two “><” chromatids counts for 2 n’s.
Mitosis:
-Start with 46 chromosomes (2n/2c).
-Replicate to become 92 chromosomes. (2n/4c)
-Pulls apart replicated chromosomes and divides to produce 46 (2n/2c) chromosomes.
Meiosis:
-Start with 46 chromosomes (2n/2c) (just like Mitosis)
-Replicate to become 92 chromosomes. (2n/4c) (Just like Mitosis).
-Meiosis I divides not like Mitosis by pulling chromosomes apart into chromatids, but instead by shuffling the full chromosomes into each of two daughter cells. Which creates (1n/2c).
-Meiosis II then divides by pulling the chromosomes apart into chromatids. Which creates (1n/1c) in each daughter cell.
This Wikipedia image may help you visualize things:
https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Meiosis_Stages.svg/1920px-Meiosis_Stages.svg.png
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