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14-06-2004, 05:04 PM | #1 |
Dragon
Join Date: Jan 2003
Posts: 2,082
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Cell Division: Mitosis & Meiosis
How do we grow? Where does the sperm and egg come from?
In this thread, you will understand more about 2 different types of cell division, mitosis (mai-toes-sis) and meiosis (may-o-sis). Mitosis is responsible for our growth where as meiosis is the initial process in the formation of the sex cells (also called gametes). --------------------------------------------------------------------------------------- Mitosis Cells in the body, excluding some type of cells in the reproductive system, undergo mitosis in order to multiply. During a certain stage in the cell life cycle, the cell will gain enough mass and initiates mitosis to take place. Mitosis occurs into our bone marrow (giving rise to new red blood cells) and also the liver tissue (allowing the liver to have a regenerative ability). Below is a simplified diagram of the different stages during mitosis. Interphase. During this phase, the nucleus of the cell contains double the number of DNA as a result of DNA replication. Once all mechanisms is in working order, the will give the "go" button and proceeds into the next phase. Prophase is where the cell division begins.
Next, I will explain to you about meiosis. --------------------------------------------------------------------------------------- Meiosis Meiosis itself consist of 2 sub-divisions, meiosis I and meiosis II. Meiosis mainly takes place in the reproductive organs which results in sperm production (spermatogenesis) and egg production (oogenesis). Below is a simplified diagram of the different stages of meiosis. Meiosis I is similar to mitosis, but one big different is that during anaphase I, the centromere remains intact. Which means that no spliting of chromosomes during meiosis I. At the end of meiosis I, 2 daughter cells will be produce, each having the same number of chromosome as a parent cell. Once meiosis I is complete and no damage is found, the 2 daughter cells proceeds into meiosis II. Meiosis II is like a second round of mitosis. This time, the centromere splits during anaphase II and at the end of meiosis II, 4 daughter cells (now called gametes) will form, but each only have half the number of chromosomes as a parent cell. From here, depending whether the organism is a male or female, the gametes will either enters into spermatogenesis or oogenesis to produce mature sperms or eggs. --------------------------------------------------------------------------------------- Here, I end the subject about cell division. Feel free to discuss with me about the topic. I will try my best to answer any doubts. And lastly, the pictures above is either taken or drawn by me, so do ask for permission or credit it of you're gonna use it. Thanks. Angel |
14-06-2004, 05:53 PM | #2 |
Dragon
Join Date: Dec 2002
Posts: 1,701
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the sister chromatids is separated during mitosis.
during meiosis 1, sister chromatids also gets separated. meiosis 2 is when the each homologus copy of the diploid chromosome get separated from each other which results in an autosomic cell. i cannot rem if the centromere hold the diplody DNA or sister chromatids or both? Last edited by thee_boss; 14-06-2004 at 06:13 PM. |
14-06-2004, 06:01 PM | #3 | ||
Dragon
Join Date: Jan 2003
Posts: 2,082
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14-06-2004, 06:15 PM | #4 |
Dragon
Join Date: Dec 2002
Posts: 1,701
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i'm the one who missed it hehe...
i've edited liao... so how? centromere hold what together??? |
14-06-2004, 06:27 PM | #5 | |
Dragon
Join Date: Jan 2003
Posts: 2,082
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14-06-2004, 09:19 PM | #6 |
Dragon
Join Date: Feb 2004
Posts: 2,739
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Reminds me of Biology I took in A-levels 13 yrs ago. Something nice to refresh my memory!!
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15-06-2004, 03:23 PM | #7 | |
Dragon
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15-06-2004, 03:45 PM | #8 | |
Dragon
Join Date: Jan 2003
Posts: 2,082
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then each sister cell (still 2n) will enter into meiosis II. During anaphase II, the amount of chromosomes will split again, this time the centromere will break. Resulting each sister cell have (n) number of chromosomes. |
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16-06-2004, 09:45 AM | #9 | |
Dragon
Join Date: Dec 2002
Posts: 1,701
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then in meiosis two, the sister chromotids split. then u got haploid cells le... yeah! in contrast for mitosis, the sister chromotids breaks while each of the resultant daughter cells maintain the two homologues thus resulting in autosomal cells(diploidy)..yeah! thanks man! |
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