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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

  • View Poll Results: Are you resitting this unit?
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    (Original post by mclovin123)
    s1? what is this? Are you talking about biol2?
    Maths, S1 = Statistics
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    (Original post by HaimishaParekh)
    I really hate that they are both on the same day! I'm so gonna flop one of them . Stupid Stats.
    Got chemistry and economics the day after... D:
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    (Original post by ??????????????????)
    Got chemistry and economics the day after... D:
    Snap :eek:
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    omgomgomgomg i'm suddenly very panicked about this exam. has anyone found or made any good summary notes?
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    anyone got any good notes on the structure and function of arteries, veins, arterioles and venules?
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    (Original post by parallal)
    Prophase is when the chromosomes coil up/condense and telophase is when they uncoil, so there will still be the same number of chromosomes. But the mass of DNA in telophase will be half that in prophase because at prophase the amount of DNA will have doubled (DNA replication) and after telophase the cell will have already have divided and the mass of DNA would have been halved. 26 chromosomes and 30 mass of DNA will be the "normal" amount.

    Because telophase and prophase are apart of mitosis they are involved in diploid cells and because a sperm cell is a haploid cell it will have half the number of chromosomes and therefore half the mass of DNA.

    Hope that helps.

    I'm a bit confused. I thought at Telophase, the chromosomes have seperated to opposite poles and have formed two new cells with identical genetic material. so how can can it have the same number of choromosomes as prophase and half mass of DNA?
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    (Original post by lolo-x)
    omgomgomgomg i'm suddenly very panicked about this exam. has anyone found or made any good summary notes?
    me too, so little time to revise after psych!!
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    I just want to make sure I have the stages of the cell cycle/mitosis right.

    Interphase - G1, S, G2, M. DNA replication occurs during S phase. (Also ATP production)
    Prophase - Nuclear envelope breaks down. The chromosomes condense/shorten/coil and become visible.
    Metapahse - Spindle forms. Chromatids attach to spindle by their centromere and line up at the centre/equator of the cell.
    Anaphase - Spindle contracts/shorten and separate the chromatids, pulling them to opposite poles.
    Telophase - Nuclear envelope develops, chromosomes uncoils and become invisible again.

    Am I missing anything?
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    the song is awful, but if you're finding meiosis hard then this really does help, its the only way i learnt it http://youtu.be/iCL6d0OwKt8
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    (Original post by lolo-x)
    omgomgomgomg i'm suddenly very panicked about this exam. has anyone found or made any good summary notes?
    what do you need help with?
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    (Original post by parallal)
    I just want to make sure I have the stages of the cell cycle/mitosis right.

    Am I missing anything?
    sounds textbook to me, good job
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    (Original post by lolo-x)
    omgomgomgomg i'm suddenly very panicked about this exam. has anyone found or made any good summary notes?
    Found some on TSR. Not sure how to send. Can't find them again.
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    Would there be any point in doing older papers before jan 2009?
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    (Original post by parallal)
    I just want to make sure I have the stages of the cell cycle/mitosis right.

    Interphase - G1, S, G2, M. DNA replication occurs during S phase. (Also ATP production)
    Prophase - Nuclear envelope breaks down. The chromosomes condense/shorten/uncoil and become visible.
    Metapahse - Spindle forms. Chromatids attach to spindle by their centromere and line up at the centre/equator of the cell.
    Anaphase - Spindle contracts/shorten and separate the chromatids, pulling them to opposite poles.
    Telophase - Nuclear envelope develops, chromosomes coil up and become invisible again.

    Am I missing anything?
    One thing you COULD add is that interphase also has the cell carrying out it's normal functions too. That's at G0.
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    (Original post by lolo-x)
    so why does the number of chromosomes stay the same shouldn't it double during interphase and then return to normal at telophase?
    Yeah it's a bit weird. But when mitosis starts, each chromosome is made up of two sister chromatids, they're genetically identical. At the end of mitosis, those sister chromatids are pulled apart, they divide at the centromere. It's kind of weird to explain, but if you counted all the 'X's at prophase it's the same as the '|' at telophase.
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    (Original post by ??????????????????)
    Got chemistry and economics the day after... D:
    So do I!

    Chem2 and Eco2?
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    I'm doing June 2010 past paper now, it's grim.
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    (Original post by Master.K)
    So do I!

    Chem2 and Eco2?
    Yup AQA and WJEC.
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    (Original post by Mina!SS)
    I'm a bit confused. I thought at Telophase, the chromosomes have seperated to opposite poles and have formed two new cells with identical genetic material. so how can can it have the same number of choromosomes as prophase and half mass of DNA?
    Not the chromosomes, the chromatids have separated.

    This is a definition of chromatid: Either of the two strands joined together by a single centromere, formed from the duplication of the chromosome during the early stages of cell division and then separate to become individual chromosome during the late stages of cell division.

    So one chromosome forms two chromatids which are separated to form one chromosome so the number of chromosomes is unchanged.

    It has half the mass of DNA because the DNA is doubled and shared between the two cells.

    I'm sorry if I'm confusing you even further.
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    (Original post by jsmith6131)
    If Fe2+ is green and haemoglobin contains Fe2+ why is our blood red
    Because it's combined with O2 and oxidised to be red
 
 
 
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