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    (Original post by darkiee)
    Is it me, or was the Januray 2011 paper a *****? I think it was the hardest so far? Am i right?
    I'll let you know my views tomorrow - You may be right though, IIRC the grade boundaries were quite low for Jan 11, relatively speaking

    On a side note, I found June 10 much harder than Jan 10.
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    Hi guys. Do u have any tips to finish this paper faster? I just managed to finish this paper with only a few seconds left and have no time to check in my trials...
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    (Original post by DLZF)
    Hi guys. Do u have any tips to finish this paper faster? I just managed to finish this paper with only a few seconds left and have no time to check in my trials...
    answer non QWC questions in bullet points?
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    oh god, dont understand why biology papers have to be so nasty!!!
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    Can anyone tell me what we need to know about DNA profiling and be kind enough to explain it?

    Any exam ques on that I seem to flop

    And could someone please explain this ques to me:

    6. DNA analysis is a reliable technique for identifying individuals. However, complications
    can sometimes arise. For example, cells from two genetically different embryos may join
    together and develop into one individual.
    This type of individual is known as a chimera.
    (a) Explain the problems of using DNA fingerprinting to identify a chimera. (3)

    MS answer:
    1. profiling depends on unique DNA / eq ;
    2. two different profiles / eq ;
    3. might use different tissue each time / eq ;
    4. needs unique profile for comparison / eq ;

    EDIT: nvm get the question now
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    (Original post by InItToWinItGetIt?)
    Can anyone tell me what we need to know about DNA profiling and be kind enough to explain it?

    Any exam ques on that I seem to flop

    And could someone please explain this ques to me:

    6. DNA analysis is a reliable technique for identifying individuals. However, complications
    can sometimes arise. For example, cells from two genetically different embryos may join
    together and develop into one individual.
    This type of individual is known as a chimera.
    (a) Explain the problems of using DNA fingerprinting to identify a chimera. (3)

    MS answer:
    1. profiling depends on unique DNA / eq ;
    2. two different profiles / eq ;
    3. might use different tissue each time / eq ;
    4. needs unique profile for comparison / eq ;
    This is to do with the restriction endonuclease enzyme cutting specic part of the dna and place in an agrose gel of buffer solution to maintain ph, a dye is added....
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    In terms of DNA profiling and gel electrophoresis, do we need to know that STRs are used or just call them DNA fragments?
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    (Original post by darkiee)
    This is to do with the restriction endonuclease enzyme cutting specic part of the dna and place in an agrose gel of buffer solution to maintain ph, a dye is added....
    Do you mean the question?

    (Original post by lbavfc)
    In terms of DNA profiling and gel electrophoresis, do we need to know that STRs are used or just call them DNA fragments?
    Think we need to know STRs. It was in one of the new spec past papers
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    Thank you. Could anyone answer me this? How do PCR and Gel Electrophoresis combine? It states that after PRC the fragments can be separated through Gel Electrophoresis, but surely the fragments made would all be the same, as PCR basically amplifies certain parts of the DNA? Or do many STR get copied during PCR?
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    (Original post by lbavfc)
    Thank you. Could anyone answer me this? How do PCR and Gel Electrophoresis combine? It states that after PRC the fragments can be separated through Gel Electrophoresis, but surely the fragments made would all be the same, as PCR basically amplifies certain parts of the DNA? Or do many STR get copied during PCR?

    PCR amplifies the STRs that have been cut from the DNA in the sample using the restriction enzyme. Basically, each cycle of PCR doubles the amount of DNA you've got from the sample. Once there is enough DNA, you can put it in the agarose gel, with a buffer solution (that conducts electricity) and pass an electric current through it (electrophoresis). The fragments obtained from the previous PCR reaction separate in the gel (smaller ones move faster and further towards positive electrode).
    You need lots of the fragments to get a good enough DNA profile, if you only have a small amount of DNA, the strands on DNA profile would be too small for us to distinguish between 2 profiles. That's why the PCR is important.
    Sorry about rambling on a bit.. Hope that's helped you
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    (Original post by InItToWinItGetIt?)
    Can anyone tell me what we need to know about DNA profiling and be kind enough to explain it?

    Any exam ques on that I seem to flop

    And could someone please explain this ques to me:

    6. DNA analysis is a reliable technique for identifying individuals. However, complications
    can sometimes arise. For example, cells from two genetically different embryos may join
    together and develop into one individual.
    This type of individual is known as a chimera.
    (a) Explain the problems of using DNA fingerprinting to identify a chimera. (3)

    MS answer:
    1. profiling depends on unique DNA / eq ;
    2. two different profiles / eq ;
    3. might use different tissue each time / eq ;
    4. needs unique profile for comparison / eq ;
    You have to apply whats given in the question. For example, cells from two genetically different embryos may join

    This gives the indication that theres 2 sets of DNA and then the MS should make sense
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    So am i right in thinking that anything from AS topics could come up? If this is correct, is it just the major topics we studied from AS or is it literally anything from what we have studied so far?

    Also, i have read some of the other threads and their are something’s that people are mentioning that i have got no clue about? Eg, about the plants and the use of nitrate to make glucose... ??? and binary reproduction ... ive never heard of this.. should i be worried??
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    (Original post by Alexandria)
    So am i right in thinking that anything from AS topics could come up? If this is correct, is it just the major topics we studied from AS or is it literally anything from what we have studied so far?

    Also, i have read some of the other threads and their are something’s that people are mentioning that i have got no clue about? Eg, about the plants and the use of nitrate to make glucose... ??? and binary reproduction ... ive never heard of this.. should i be worried??
    That must nt b Edexcel lol
    Sm other Board probably So chill

    And yea it's supposed to b a 'Synoptic' ppr .. Last year the Q regarding the Structure of Cellulose poppd up ... Who knows what they might come up wd this tym ..But yea it's prolly the Major ones yu need to worry abt! .. Bsta Luck!

    Mahn What a Drag! I haven't evn fininsd my unit 4 Prep!! Talk abt revising AS! :eek::eek::eek::eek:
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    OOOooo thank god!! i was panicing biggg time!!

    i was wondering if someone could explain what a "satellite" is... refering to DNA profiling ... is it just another word for a STR?
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    (Original post by Alexandria)
    OOOooo thank god!! i was panicing biggg time!!

    i was wondering if someone could explain what a "satellite" is... refering to DNA profiling ... is it just another word for a STR?
    yup
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    (Original post by dnamoore)
    You have to apply whats given in the question. For example, cells from two genetically different embryos may join

    This gives the indication that theres 2 sets of DNA and then the MS should make sense
    Yeah get it now. Thanks
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    hey guys, can some just go over all the practicals we need to know in this unit?
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    edexcel won't let me get the past papers
    can somebody please give me a link to where i can get some past papers from...
    thanx
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    can anybody tell me what exactly we need to know about wiggle matching?
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    (Original post by Schoolio93)
    can anybody tell me what exactly we need to know about wiggle matching?
    what the..? is that even on the spec?
 
 
 

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