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    I'm getting really confused with action potentials and summations and the All-or-nothing principle, can anyone help?
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    Can someone explain to me where you would find actin and myosin in these: dark band, light band, hone and z line?
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    (Original post by jessiebon)
    Yes maybe but I would struggle to put much unit 5 into that.
    I'd go with endotherms and ectotherms, rod and cone cells maybe because some species can only see in black and white light?
    Hmm, any ideas?
    Probably haemoglobin and surface area: volume ratio from Unit 2
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    (Original post by Kale1111)
    Can someone explain to me where you would find actin and myosin in these: dark band, light band, hone and z line?

    dark - actin/myosin (stays the same during contraction)
    light - actin only (decreases in length during contraction)
    z-line - end of sarcomere
    H zone - myosin only
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    Any predictions for essay titles? Need to practice!
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    And do you think there's much point learning about things in unit 1 such as pressure changes in cardiac Cycle for the essay? Because I don't see how an essay title could allow you to write about it!
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    so what essays would you guys be happy to come up?
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    (Original post by lkos)
    I'm getting really confused with action potentials and summations and the All-or-nothing principle, can anyone help?
    All or nothing principle - Action potentials cannot vary in size, the strength of a stimulus is indicated by the frequency of the nerve impulse.

    Temporal summation - Where two or more nerve impulses (action potentials) arrive in quick succession down the same neurone, due to the high threshold of the post synaptic membrane.

    Spatial summation - Where two or more nerve impulses arrive at the same time down different neurons due to the high threshold of the post synaptic membrane.

    Action potentials - Depolarisation, repolarisation and hyperpolarisation.

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    (Original post by Hollyh12345)
    And do you think there's much point learning about things in unit 1 such as pressure changes in cardiac Cycle for the essay? Because I don't see how an essay title could allow you to write about it!
    If the essay was about cycles then it could be of use.
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    So going back to basics, can someone explain to me protein structure, just incase it comes up in the essay and I have completely forgotten
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    Hi, does anyone know why the answer to question 5b in the June 2011 paper is 2? How would you know that both restriction sites are in the DNA fragment and not else where in the plasmid? Thanks
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    (Original post by Maryam.M)
    Hi, does anyone know why the answer to question 5b in the June 2011 paper is 2? How would you know that both restriction sites are in the DNA fragment and not else where in the plasmid? Thanks
    Just doing that now too, was about to ask the same thing, did you do the first question? Again it says cut once but two fragments? Always 1 less than I think?
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    (Original post by Maryam.M)
    Hi, does anyone know why the answer to question 5b in the June 2011 paper is 2? How would you know that both restriction sites are in the DNA fragment and not else where in the plasmid? Thanks
    Hi ive just done this paper! they key is they are using another plasmid not the same one. we also get told there's 3 pieces but there's only one binding site shown on the known plasmid. To get 3 pieces the plasmid needs to be cut 3 times,so we therefore know that there is 2 in the unknown DNA. it took me a while to work out but i hope this helps and makes sense !
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    (Original post by bg9876)
    Just doing that now too, was about to ask the same thing, did you do the first question? Again it says cut once but two fragments? Always 1 less than I think?
    i think of it as a rubber band or a hair bobble if you snap it there is still one piece i know weird analogy but it seems to help me
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    (Original post by charlottexheath)
    Yes- it's used in paternity testing as 50% of DNA is from Mother and 50% from Father, so you can compare the base sequences- hence it's also used in breeding of animals. Then also used in forensics to identify a criminal
    Thanks
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    (Original post by xSophie04x)
    Hi ive just done this paper! they key is they are using another plasmid not the same one. we also get told there's 3 pieces but there's only one binding site shown on the known plasmid. To get 3 pieces the plasmid needs to be cut 3 times,so we therefore know that there is 2 in the unknown DNA. it took me a while to work out but i hope this helps and makes sense !
    So there are 3 cuts, but you don't include one as they already know about that one/not in the DNA they are trying to sequence? Thanks
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    (Original post by bg9876)
    Just doing that now too, was about to ask the same thing, did you do the first question? Again it says cut once but two fragments? Always 1 less than I think?
    it's 2 because you know there is one cutting site for BamH1 in the original plasmid, but you end up with 3 fragments, so to get three fragments there have to be 2 more cutting sites for BamH1 and seeing as we know they aren't in the original plasmid they have to be in the unknown length
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    yep that it uw

    (Original post by bg9876)
    So there are 3 cuts, but you don't include one as they already know about that one/not in the DNA they are trying to sequence? Thanks
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    (Original post by jessicasydes1)
    My teacher is really high up in aqa and she said that what happened in psychology with some doing the reserve and some not is never happened before so hopefully if it happens tomorrow they'll just lower the grade boundaries overall so it's easier for us
    You wanna ask your teacher what the essays gonna be on tomorrow
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    (Original post by xSophie04x)
    Hi ive just done this paper! they key is they are using another plasmid not the same one. we also get told there's 3 pieces but there's only one binding site shown on the known plasmid. To get 3 pieces the plasmid needs to be cut 3 times,so we therefore know that there is 2 in the unknown DNA. it took me a while to work out but i hope this helps and makes sense !
    Oh I see thank you so much, and good luck for tomorrow!
 
 
 
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