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    (Original post by I Hate Edexcel)
    Do we need to know how anabolic steroids work?
    I like your username.
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    (Original post by Mjwilson1988)
    Start by identifying the gene which is cancer causing (might be a Protoncogene etc).

    Isolate it and remove it using Restriction Enzymes (Restriction endonuclease is an example).

    Amplify it (copy it) using the Polymerase chain reaction, mention how you use DNA Polymerase to do this. Now you've got a load of copies, you need to insert it into a vector.

    Choose a Vector, such as a virus or a bacteria, I'll go for Bacteria, as I like the Plasmids. Using a Plasmid you need to open the ring of DNA (again, using Restriction Enzymes), and insert the gene into it, the enzyme used to fix a gene into a plasmid is call DNA Ligase. Now insert the plasmid into Bacteria (usually done by just mixing it with Bacteria and then killing off the ones who don't have the plasmid so you're just left with the ones who have the plasmid)

    Infect the rat with the bacteria/virus/whatever vector. The vector will carry the gene into the cells of the rat. The Cancer causing Gene will now be fused with the DNA of the rat and will be expressed, causing cancerous cell growth in the rat.
    This is perfect! Thanks!
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    (Original post by joan2468)
    Thanks for the answers guys, but I was wondering about the blood pressure during exercise - I thought if you need blood to flow faster to the muscles you need higher blood pressure? I'm thinking higher pressure = blood travels faster, but I'm not sure about this...
    Let's think about this from the beginning.
    when exercise begins, heart rate increases so blood travels faster
    as a result blood pressure increases
    there is more input of blood into the heart
    so ventricles contract more strongly (higher stroke volume)
    this means that blood pressure increases again
    which means that blood travels faster

    i think this is an example of positive feedback
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    This exam is evil. SO MUCH CONTENT TO COVER.
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    (Original post by I Hate Edexcel)
    This exam is evil. SO MUCH CONTENT TO COVER.
    How much have you covered so far? Less than 21 hours to go.

    I really gotta make this one count. I felt I did crappy in Unit 4.
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    (Original post by joan2468)
    Thanks for the answers guys, but I was wondering about the blood pressure during exercise - I thought if you need blood to flow faster to the muscles you need higher blood pressure? I'm thinking higher pressure = blood travels faster, but I'm not sure about this...
    when your blood vessels dilate it means the diameter of the arterioles widen so less 'force' is needed to push the blood through, therefore blood pressure decreases. so the wider the diameter, the lower the pressure.
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    Does anyone have the mark scheme for this paper which opens as a pdf?
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    (Original post by EstebanK0)
    How much have you covered so far? Less than 21 hours to go.

    I really gotta make this one count. I felt I did crappy in Unit 4.
    I've done a lot, but still have a lot to go. Thankfully I did unit 4 back in Jan.
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    (Original post by Lujain Al Omari)
    Let's think about this from the beginning.
    when exercise begins, heart rate increases so blood travels faster
    as a result blood pressure increases
    there is more input of blood into the heart
    so ventricles contract more strongly (higher stroke volume)
    this means that blood pressure increases again
    which means that blood travels faster

    i think this is an example of positive feedback

    Hmm... that makes sense mind if you explain how does a positive feedback work? it happens during hypothermia right?
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    hello, could anyone explain this bit in the mark scheme please? The question was about comparing auxins to hormonal control:

    4. speed of action compared e.g. slower in plants,
    some animal hormones are faster ;
    5. duration of effect compared e.g. some animal
    hormones have a shorter term effect ;

    Why is speed faster in animals? is it just the fact that the hormones reach their target faster in blood?
    And also, the whole duration thing. I thought animals would have a longer duration, such as testosterone effecting males over years, whereas auxins take a few hours.. But I understand that something like adrenalin would take a shorter time than Auxins. So would either be acceptable - the mark scheme is SO ambigious?
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    (Original post by iwantopas19)
    u sure thats right? cuz ive read too many posts regarding that none of which is alike!.
    well all i basically know from my revision is that
    plants detect light with phytoreceptors called pytochromes. They are founds leaves seeds roots and stem. The control lots of resposes such as flowring in different seasons
    So basically the pytochrome aborble light. There it PFR(730) and Pr(660)
    When there is red light it gets converted PR-PFR
    when far red light PFR-PR
    When darkness
    PFR0PR
    Daylight has more red light than far red light , the amount the phytochromes change depend on the the amount of light
    The benifits of having these are that flowering will happen at the right time
    It is better than a stimulus like temperature
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    For anybody still stuck on the pre-release revision, I have uploaded a document which may be of use.
    http://getrevising.co.uk/resources/p...tions_practice
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    (Original post by iwantopas19)
    where can i get the specimen ? :/
    http://www.edexcel.com/migrationdocu...ce-biology.pdf
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    Anyone got the pre-release material for PAST PAPERS? (So we can do Section C of past papers)
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    (Original post by bubblegummer)
    Hmm... that makes sense mind if you explain how does a positive feedback work? it happens during hypothermia right?
    positive feedback is when effectors promote a change. For example, in the case of the development of athersclerosis, blood pressure is the cause. It damages the endothelial lining of arteries, so platelets clump on the wound. Cholesterol then settles on the clump, forming and atheroma. This increases blood pressure further, so more damage occurs....

    I'm not sure what you mean by hypothermia in this context. Can you elaborate?
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    (Original post by Lujain Al Omari)
    positive feedback is when effectors promote a change. For example, in the case of the development of athersclerosis, blood pressure is the cause. It damages the endothelial lining of arteries, so platelets clump on the wound. Cholesterol then settles on the clump, forming and atheroma. This increases blood pressure further, so more damage occurs....

    I'm not sure what you mean by hypothermia in this context. Can you elaborate?
    so whats the difference between negative feedback and positive feedback?
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    (Original post by TheNoobyPotato)
    hello, could anyone explain this bit in the mark scheme please? The question was about comparing auxins to hormonal control:

    4. speed of action compared e.g. slower in plants,
    some animal hormones are faster ;
    5. duration of effect compared e.g. some animal
    hormones have a shorter term effect ;

    Why is speed faster in animals? is it just the fact that the hormones reach their target faster in blood?
    And also, the whole duration thing. I thought animals would have a longer duration, such as testosterone effecting males over years, whereas auxins take a few hours.. But I understand that something like adrenalin would take a shorter time than Auxins. So would either be acceptable - the mark scheme is SO ambigious?
    All your deductions are correct. Some hormones travel faster in blood and have shorter effect (Adrenaline), others have long term effect (testosterone)
    Keep in mind the mark scheme keeps saying 'some'
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    (Original post by I Hate Edexcel)
    I've done a lot, but still have a lot to go. Thankfully I did unit 4 back in Jan.
    Mind telling, what grade did you achieve?
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    (Original post by Sravya)
    so whats the difference between negative feedback and positive feedback?
    negative feedback is when the effectors oppose the change occurring.
    For example, core body temperature rises, this is detected by thermoreceptors that send impulses to the hypothalamus, the hypothalamus causes sweat glands to produce and release more sweat, core body temperature increases, this is detected by thermoreceptors, hypothalamus stops send impulses to the sweat gland, so sweating stops
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    (Original post by Lujain Al Omari)
    negative feedback is when the effectors oppose the change occurring.
    For example, core body temperature rises, this is detected by thermoreceptors that send impulses to the hypothalamus, the hypothalamus causes sweat glands to produce and release more sweat, core body temperature increases, this is detected by thermoreceptors, hypothalamus stops send impulses to the sweat gland, so sweating stops
    Thanks
 
 
 
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