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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 watch

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    (Original post by snowgirl61862)
    Hey can anyone answer this question for me?
    The Nelson Thornes textbook states on P143 that when organisms display kinesis, the more unpleasant the stimulus the more rapidly they move and the more rapidly they change direction. However in the CGP guide, it says that the more unpleasant the stimulus the more rapidly they move and the slower they change direction. They contradict! So which is correct?

    I feel more included to trust the endorsed textbook, however the CGP book seems to make more logical sense. So according to CGP: in nice conditions they change direction a lot, so essentially they stay in the ideal area, and in horrible conditions they move in a straight line, so they would leave the nasty area quicker.

    And the textbook reckons when in a nice place they dont change direction much, and in unpleasant areas they change direction more rapidly. Hmmm.

    Please help?
    This confused me for a while too.. :confused: my teacher explained it in a way thats kind of easy to understand.
    And this is how she explained it..
    Imagine youre in a classroom and there was a really nasty smell in one corner close to where youre stood and you want to get away from it as quickly as possible...
    If you make lots of little turns youre just gonna end up going in circles and not actually getting far away from it. However if you make a few turns every now and then you get further away. Hope that helps
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    (Original post by Flux_Pav)
    that is incorrect. Klinokinesis - random movement in which rate is related to stimulus intensity
    woodlice move more in pleasant environments. if they change direction less, they move in straight line so they will move out the area.
    We've been taught it the other way round, that the more unpleasant the surroundings are the more rapidly they move and more times they change directions. :dontknow: Still, I suspect that if there is a kinesis question in the paper it'll be obvious which case it is as it's a perfect one to use 'in context'.
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    (Original post by Tericon)
    PCR involves a reaction mixture of DNA polymerase, free DNA nucleotides, primers and the DNA strand to be copied.

    1. Heat reaction mixture to 95 degrees to break the hydrogen bonds between bases and so to uncoil the DNA strand.

    2. Mixture cooled to 65 degrees. Primers; each with a complementary base sequence to the start of each strand, anneal to each polynucleotide strand.

    3. Mixture heated to 72 degrees so DNA polymerase can work. DNA polymerase lines up free DNA nucletides on each strand and hydrogen bonds form between bases due to specfic base pairing.

    4. Two new copies of DNA fragment formed, one cycle PCR complete

    5. Each cycle double the amount of DNA strands,

    PCR is in vitro cloning, cloning of a fragment of DNA outside of a living organims, whereas DNA replication happens inside a living organism: so in vivo cloning. DNA helicase is required for DNA replication, whereas for PCR it is not. Finally, DNA replication involves the whole of DNA being replicated, whereas PCR involves just a fragment.

    I hate genetic engineering. PCR, Restriction Endonucleases and Reverse Transcriptase are the only bits I understand
    My book says cool it to 55C... :/
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    (Original post by Ineluctable)
    The Nelson Thornes book has two pages on cystic fibrosis, but there is no mention of it in the specification. Do we even need to learn it?
    I wasnt sure about this either! But I have learnt it just incase, because it wouldn't be in the book in so much detail if we didn't... would it????
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    I cannot get motivated for this exam! It's awful.

    And I can't get my head around siRNA. I read it, I write it down, I do questions on it, but it's still not sticking.
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    (Original post by Jing_jing)
    We've been taught it the other way round, that the more unpleasant the surroundings are the more rapidly they move and more times they change directions. :dontknow: Still, I suspect that if there is a kinesis question in the paper it'll be obvious which case it is as it's a perfect one to use 'in context'.
    You are both right. I'm sure in unfavourable situations woodlice move rapidly with less emphasis on turning randomly, whereas in favourable situations they simply turn randomly.
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    (Original post by appleschnapps)
    I cannot get motivated for this exam! It's awful.

    And I can't get my head around siRNA. I read it, I write it down, I do questions on it, but it's still not sticking.
    Hey what part of it dont you get? Its one of the things that I didn't get initially but do understand now as part of the genetics sections so I'll try to help out
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    (Original post by appleschnapps)
    I cannot get motivated for this exam! It's awful.

    And I can't get my head around siRNA. I read it, I write it down, I do questions on it, but it's still not sticking.
    I have the same problem with siRNA. It doesn't help that the textbooks and my class notes all say different things
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    (Original post by LettersFromTheSky)
    Hey what part of it dont you get? Its one of the things that I didn't get initially but do understand now as part of the genetics sections so I'll try to help out
    I suppose I don't really understand its applications, and where the associated proteins come from. I think I could explain how it works, but I'd be thrown off from a question if it didn't ask about siRNA directly.
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    (Original post by Boo!xx)
    My book says cool it to 55C... :/
    Mine says between 50 degrees and 65, i just picked one value to remember, I can't imagine them penalising you for not stating the range, a value within the range should be fine, I'll probably put 'approx 65'.
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    (Original post by appleschnapps)
    I suppose I don't really understand its applications, and where the associated proteins come from. I think I could explain how it works, but I'd be thrown off from a question if it didn't ask about siRNA directly.
    If you know the process you will be fine I think. I don't think we have to know too much about where the associated proteins come from, my tb doesnt mention that (the NT one).

    I think the main point apart from the process you have to know is that siRNA prevents mRNA from being translated, so no polypeptide will be formed, and therefore the gene is not expressed.

    The NT book says its potential uses could be to use siRNA to block certain genes from being expressed which could be used to prevent genetic diseases.

    Also it can be used to identify the role of genes. For example if an siRNA modeluce is added to cells, the effects of this can be observed and it can be determined what the role of the gene is.

    I hope this helped , sorry if it didn't.
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    (Original post by LettersFromTheSky)
    If you know the process you will be fine I think. I don't think we have to know too much about where the associated proteins come from, my tb doesnt mention that (the NT one).

    I think the main point apart from the process you have to know is that siRNA prevents mRNA from being translated, so no polypeptide will be formed, and therefore the gene is not expressed.

    The NT book says its potential uses could be to use siRNA to block certain genes from being expressed which could be used to prevent genetic diseases.

    Also it can be used to identify the role of genes. For example if an siRNA modeluce is added to cells, the effects of this can be observed and it can be determined what the role of the gene is.

    I hope this helped , sorry if it didn't.
    Nah, that's good to hear. I think at the moment I'm just scared my brain will switch off and it'll be all: haha, you want me to tell you what impact ____ has on gene expression? No.
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    Control of transcription - only some genes transcribed
    Control of translation - mRNA destroyed or translation blocked by ribosome

    How mRNA is destroyed?
    -RDR's synthesise dsRNA (double stranded RNA) by using the mRNA as a template
    -dsRNA is hydrolysed into siRNA (small interfering RNA)
    -the siRNA molecules are taken up by a protein complex
    -the protein complex separates the two strands and gets rid of one strand
    -the protein complex keeps the strand that is complementary to the mRNA template
    -the protein complex moves to mRNA molecules in cytoplasm and as it contains a complementary strand to mRNA, the strand in the protein complex binds to mRNA
    -once attached, the mRNA is destroyed and so it cannot be translated

    something like that even though this is written from what i can remember
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    did anyone do the bio4 paper i heard that there wasent alot of hsw in the paper is this true
    i hope there isnt alot of hsw in the bio5 paper
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    (Original post by SashaLuLu)
    I think it is that the anatoxin is going to bind to the receptors. This will result an action potential being generated as sodium ions diffuse in. However, you know acetylcholinesterase breaks down acetylcholine which allows the action potential to stop, well the anatoxin cannot be broken down by acetylcholinesterase and so anatoxin is producing tears but it is causing excessive production as it is always producing an action potential which stimulates the production of tears. As the anatoxin cannot be broken down you are still getting action potentials therefore lots of tears.
    Also correct me if i am wrong but an action potential doesn't just have to happen at a muscle right? so the action potential can be stimulated somewhere to do with tears??

    I don't know if it's right, but that's what i would guess!
    Hmm alright, thank you I didn't think of the fact that it might be connected directly to the production of tears, so thank you
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    Hi guys, I am stuck now on an exam style question from the nelson thornes textbook and I was wondering if anyone could help me out? It is page 210, question 3C? (It is a question from the homeostasis section based on the control of blood glucose?)
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    (Original post by hahaff)
    did anyone do the bio4 paper i heard that there wasent alot of hsw in the paper is this true
    i hope there isnt alot of hsw in the bio5 paper
    Yes, not much HSW at all for once! There's always one big HSW question in this unit, according to my biology teacher, question 10, the one before the essay.
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    (Original post by Tericon)
    Yes, not much HSW at all for once! There's always one big HSW question in this unit, according to my biology teacher, question 10, the one before the essay.
    Yeah they always have a data analysis question right before the essay. Think it's 15 marks worth... As if the essay wasn't bad enough!
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    Is there a Q&A thread thing - I find that a pretty good way of revising bio...?
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    (Original post by LettersFromTheSky)
    If you know the process you will be fine I think. I don't think we have to know too much about where the associated proteins come from, my tb doesnt mention that (the NT one).

    I think the main point apart from the process you have to know is that siRNA prevents mRNA from being translated, so no polypeptide will be formed, and therefore the gene is not expressed.

    The NT book says its potential uses could be to use siRNA to block certain genes from being expressed which could be used to prevent genetic diseases.

    Also it can be used to identify the role of genes. For example if an siRNA modeluce is added to cells, the effects of this can be observed and it can be determined what the role of the gene is.

    I hope this helped , sorry if it didn't.
    Yeah I agree - with these type of things I think the important bit is understanding the process and then the application bit will be tested in the exam by applying it to a scenaero.

    Just for the record I have got sRNA can...

    - Silence undesirable genes (i.e. GM crops or in cancer treatment)

    - Identify gene function by silencing certain genes and observing the effects
 
 
 
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