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    (Original post by Hilton184)
    Spec says we only have to 'evaluate' evidence for chemiosmosis so I don't think we have to recall it, I wouldn't bother learning it.

    But something along the lines of...

    pH of inter membrane space much lower than pH of matrix.
    Disrupting ATP synthase enzyme prevents production of ATP, but electron transport chain still occurs.


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    Couldn't thank you enough !
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    (Original post by goonieskellie)
    Hey guys, just wondering what roughly the grade boundaries are for A*s on the past papers? both F214 and F215? I know they don't mark it like that, but just wondering as a rough guide (:
    OCR release their 90% boundaries each year, you just have to search "OCR grade boundaries 90 conversion" instead. There's also the 100% cap marks around on WhatDoTheyKnow.

    I have the 90% and 100% conversions except for June 2014 attached, but I believe they more or less matched the June 2011 boundaries.
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    (Original post by medactuary)
    - genomic DNA mapped using a micro satellite
    - DNA broken down into sections of 100,000 base pairs
    - Place each section into separate BACs and place the BACs into E.coli (by transformation). They will divide and form clone libraries. Each colony will contain copies of the same section of DNA.
    - DNA extracted from E.coli and restriction enzymes cut them up into smaller fragments. We have more than one piece of the same section so we get overlapping fragments if we use different restriction enzymes as they cut the sections at different places.
    - Electrophoresis - fragments separated according to size can anyone confirm that electrophoresis occurs here and not after fluorescent-chain terminating nucleotides are added?
    - Sequence DNA by adding free nucleotides. When a fluorescent chain-terminating nucleotides is added no more nucleotides are added. This will happen repeatedly with each 'overlapping fragment' and the idea is if you do it enough times every base should have been 'hit' by a fluorescent-chain terminating nucleotide so you can work out what each base is in your section of DNA.
    - Computer compares overlapping regions to assemble the DNA sequence of the section you placed into the BAC.
    - Overlapping sections of DNA mapped to place all of these BAC sections in the correct order.
    - Each DNA section is sub-cloned into plasmids as automated sequencing of small section of DNA in plasmids carried out
    Yeah i'm wondering the same thing about the bit in bold!
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    (Original post by bakedbeans247)
    Yeah i'm wondering the same thing about the bit in bold!
    I would think you do your gel electrophoresis after adding your fluorescent terminator bases, so you can actually sequence the gene. Fluorescent terminator bases added; process of interrupted PCR. Hence you get fragments of all different lengths, depending on where the terminator base was added.

    Lengths are separated by size - put into size order - by process of gel electrophoresis. Base sequence of fragments read/identified. This occurs because the terminator bases at the end of each fragment fluoresce, so you can determine the sequence because each base; ATCG; fluoresce different colours.


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    (Original post by medactuary)
    - genomic DNA mapped using a micro satellite
    - DNA broken down into sections of 100,000 base pairs
    - Place each section into separate BACs and place the BACs into E.coli (by transformation). They will divide and form clone libraries. Each colony will contain copies of the same section of DNA.
    - DNA extracted from E.coli and restriction enzymes cut them up into smaller fragments. We have more than one piece of the same section so we get overlapping fragments if we use different restriction enzymes as they cut the sections at different places.
    - Electrophoresis - fragments separated according to size can anyone confirm that electrophoresis occurs here and not after fluorescent-chain terminating nucleotides are added?
    - Sequence DNA by adding free nucleotides. When a fluorescent chain-terminating nucleotides is added no more nucleotides are added. This will happen repeatedly with each 'overlapping fragment' and the idea is if you do it enough times every base should have been 'hit' by a fluorescent-chain terminating nucleotide so you can work out what each base is in your section of DNA.
    - Computer compares overlapping regions to assemble the DNA sequence of the section you placed into the BAC.
    - Overlapping sections of DNA mapped to place all of these BAC sections in the correct order.
    - Each DNA section is sub-cloned into plasmids as automated sequencing of small section of DNA in plasmids carried out
    That's brilliant, has really helped, thank you
    I'd agree with Hilton, it would make sense to form the frgments of DNA and then seperate them via electrophoresis in order to determine the sequence
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    (Original post by bakedbeans247)
    Yeah i'm wondering the same thing about the bit in bold!

    Wouldn't it be simpler to use the sanger (chain termination) method ? as that seems like a hell of a lot to write
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    What's the difference between chiasma and chiasmata? In one mark scheme they only allowed chiasmata
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    (Original post by medactuary)
    What's the difference between chiasma and chiasmata? In one mark scheme they only allowed chiasmata
    Chiasma is the singular and chiasmata is plural. Best to say chiasmata as there is likely to be more than one point of crossing over.
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    (Original post by bbadonde2)
    Chiasma is the singular and chiasmata is plural. Best to say chiasmata as there is likely to be more than one point of crossing over.
    ah i see thanks!
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    (Original post by ParzivaI)
    That's brilliant, has really helped, thank you
    I'd agree with Hilton, it would make sense to form the frgments of DNA and then seperate them via electrophoresis in order to determine the sequence
    I'm not sure if this answers what people were asking about when electrophoresis occurs but i went to see my teacher this morning and these are the notes he gave me; - Bearing in mind he usually helps to write and mark F215

    1. DNA extracted from cells

    2. DNA cut using restriction endonucelease enzymes. This produces nucleotides about 100,000 base pairs in length

    3. The DNA fragments are inserted into a BAC and then into e coli

    4. This is allowed to grow in culture so many copies of the DNA are made

    5. DNA is extracted from e coli and cut using a range of restriction endonuclease enzymes. This ensures the DNA is cut in different places and so produces overlapping fragments that are easy to sequence

    6. Then the fragments are separated by gel electrophoresis ( a little bit of extra detail is needed into how this works)

    7. The fragments are then labelled with DNA probes ( a bit of extra detail on how this works is needed too)

    8. Copies of the fragments are made by PCR

    9. The fragments are heated to produce single stranded DNA. Primers are added which bind to DNA and allow DNA polymerase to copy the strand.

    10. Free DNA nucleotides are added which contain fluorescent dye, each base is dyed a different colour. Some bases are double deoxidised which means they stop the chain there

    11. This produces strands of DNA that are different lengths

    12. The fragments are separated by gel electrophoresis again

    13. The dyed bases are read and this produces a sequence of bases that makes up the genome. The fact that the DNA is different lengths means there is overlap so the whole of the genome sequence is mapped.

    He also said we would be unlikely to get a question asking for the whole of this sequence (although not impossible) and more likely to get a question asking about how electrophoresis, DNA probing or PCR work.

    I'm not sure if that helps anyone at all but i thought i'd pass this along
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    wow thank you! has he given you anymore notes like this? could you please share them?

    Also what is meant by DNA probing?
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    (Original post by medactuary)
    wow thank you! has he given you anymore notes like this? could you please share them?

    Also what is meant by DNA probing?
    Not yet, that was just a topic i went to him with that i didn't understand. But if i get some more i'll be sure to share them.

    I haven't actually revised that yet but my revision guide says 'a DNA probe is a short length of DNA that is used to identify different genes with a specific nucelotide sequence'. So after the first round of electrophoresis using DNA probes is a way to identify which bases are in that particular fragment.
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    Thanks Maisie, those notes are great, makes sense now.

    (Original post by medactuary)

    Also what is meant by DNA probing?
    DNA probes are short single-stranded lengths of DNA that will bind to complemantary exposed DNA strands. The probes are tagged with flourescence or radioactive isotopes so that once the DNA probes have binded (hydrogen bonds) the DNA fragments become visible and can be identified.
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    aren't all of this information people are looking for about sequencing and DNA probes all in the book?
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    (Original post by jjblok)
    aren't all of this information people are looking for about sequencing and DNA probes all in the book?
    Yeah it is, just sometimes i find getting it set out differently lets you see it in a different light, and sometimes it makes more sense. Also sometimes the book adds in extra knowledge that isn't in the spec and actually makes things a little confusing
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    thank you!!!
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    Any predictions ?


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    (Original post by ChoccyPhilly)
    Couple of tiny corrections:

    CA ions bind to troponin, causing troponin to change shape and pull tropomyosin out of the actin-myosin binding site. Tropomyosin's shape does not change.

    The unit isn't a myofibril, it's a sarcomere.
    Oops. Sorry for the mistake. Hope this doesn't cause any confusion. I meant to write that the sarcomere is a unit of a myofibril. I should've checked before posting. Sorry again.
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    Can anyone give me any tips on interpreting command words like "explain" "Suggest" Like is there a special trick?
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    Hey can someone please send me the F214 and F215 past papers from 2014 please? I really need to do them. Thanks


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