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Meiosis/mitosis for AQA simple numbers watch

    • Thread Starter

    Ok this is how i understand mitosis and meiosis, its more the number of chromosomes that's involved that gets me.

    Start with 46 chromosomes
    double this to 92
    split this once, 23 pairs again 2 daughter cells produced
    split this again by mitosis leaves only 23 individual chromosomes not 23 pairs but 4 gamates?

    is this right?

    Start with 46 chromatids (invidiual chromosomes)
    double each chromosome up to give 46 pairs or 92 individual chromosomes
    half this to 23 chromosomes becase 2 daughter cells produced.
    each new cell has 23 pairs of chromosomes.

    anyone care to put me right as i'm sure i'm wrong on tihs? Particularly in regards to when the chromosomes double in meiosis, BECAUSE they must double, if you are producing 4 gamates each with 23 individual chromosomes. you can't get this from a single body well with only 46 chromosomes because 46/4 doesn't = 23? So when exsactly/how exsactly does it mulitply.

    also does anyone know if we need to know about i think its TCP the building blocks of DNA? for GCSE AQA?

    Yeah, sounds good to me and it's actually quite impressive that you understand it that well for gcse.

    As you asked, DNA replication takes place in both meiosis and mitosis during a phase known as interphase.

    Basically, after a cell is formed by mitosis, it goes through interphase. There are two parts to this. At the first stage (G1) new proteins and organelles are synthesised and during (G2) the DNA replicated, which doubles the DNA in a cell. This allows the cell to undergo mitosis again.

    This new cell then goes through interphase again and the same thing happens again. It is a continuous cycle and is known as the cell cycle.
    • Thread Starter

    So interphase or a process similar to it happens just before meiosis to the cell that's going to be made into the 4 sperm?

    Also this cell division cannot go on forever in all the organs of the body can it for example the liver cannot repair itself does this mean that after initial growth i.e. puberty the liver never grows again?
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