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

  • View Poll Results: Are you resitting this unit?
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    Hi could soon clear something up for me, in DNA sequencing, each test tube has DNA fragment + modified nucleotide + bank of nucleotides + radiotactive primer+ DNA polymerase.

    Surely the fact that the primer will have to attach to some bases at the beginning of the fragment means that when you read off the sequence on the electrophoresis gel you'll be reading from the last nucleotide on the primer - not the beginning of the DNA fragment?
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    (Original post by Aiboz)
    Well how I remember is it that we have two ways - increase of a heartbeat and slowing of a heartbeat.

    So when we exercise there is an increase in metabolic/muscular activity, this increases the rate of respiration and thereby increase the level of carbon dioxide in the blood. When carbon dioxide is dissolved in solution it becomes acidic. So this increased level of carbon dioxide lowers the pH level. The chemoreceptors in the walls of the carotid arteries (the arteries that serve the brain) detect this and send signals to the medualla oblongata in the brain. The centre in the medulla oblongata that increases heart rate increases the frequency of impulses to the sinoatrial node via the sympathetic system. The sinoatrial node increases the heart beat. This causes increased blood flow, which removes the carbon dioxide from the lungs faster. This means carbon dioxide levels decrease back to normal.

    If this helps, quote me. I will then explain the control in slowing down the heartbeat and pressure receptors.
    Thankssss! That was soo much help I think i'll just end up forgetting the proper words, like sympathetic and parasympathetic. Do we have to know the proper channels and stuff it goes down?
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    (Original post by blackberryaddict)
    Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

    A* 69
    A 62
    B 55
    C 49
    D 43
    E 37
    That made me feel better, those aren't too bad
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    Think oestrous cycle will come up again?
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    (Original post by blackberryaddict)
    Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

    A* 69
    A 62
    B 55
    C 49
    D 43
    E 37
    wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!
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    (Original post by sarahlovesleon)
    wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!
    But that is just one paper, which people found difficult, the examiners report is full of 'a poorly answered question' and such phrases.

    This one may have higher grade boundaries, it all depends on how well prepared people are and how the questions are worded.
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    (Original post by johnsoloman)
    Hey, is anyone bothering to learn AS biology or at least go over it for the synoptic essay tomorrow?
    I'm not sure whether I should or not, as i haven't got much time left
    its too much information so i dont think ill bother :/ at least if you focus on this topic you can do well on the questions and then at least write about A level stuff in the essay - and if you remember AS stuff - its a bonus
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    (Original post by Tericon)
    Your diagram is fantastic, but I'm still a little confused...

    I get that 2 must be nearest the label as its the radioactive fragment, but its the partial digests that confuse me, they add up to more than 10? How can this be?

    How to find the fragment nearest the radioactive label is pretty much the only bit of RM i get

    (Original post by blackberryaddict)
    Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

    A* 69
    A 62
    B 55
    C 49
    D 43
    E 37
    Thanks a lot ! Grade boundaries look significantly higher compared to Unit 4 even though this unit is a lot harder. So does that mean that people can't re sit this exam in January?
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    (Original post by sarahlovesleon)
    wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!
    Yeah out of 100. Haha getting 20 on the essay is easier said than done though. And I think the bit people haven't really prepared for. What the essay topic is will make or break me. Oh god the pressure with Uni offer
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    Someone tell me what I need to know from As since Ive almost forgotten the entire As

    +rep

    Also which legacy paper is more similar
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    (Original post by mkb230)
    Thanks a lot ! Grade boundaries look significantly higher compared to Unit 4 even though this unit is a lot harder. So does that mean that people can't re sit this exam in January?
    No you have to wait for the summer
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    (Original post by Jin3011)
    The bases on the mutated gene are determines by DNA sequencing and stored in genetic libraries.
    A fragment of DNA that has bases complementary to the mutated portion of the gene is produced.
    The DNA fragment is radioactively labelled to produce a DNA probe (or the nucleotides are radioactively labelled to be more accurate)
    And PCR is used to produce many compies of this DNA probe using radioactive nuclotides rather than normal ones.
    After you've used the single stranded DNA to a make the double strand in PCR do you use DNA helicase to seperate them, or just heat?

    Also how do you locate which gene is mutated?
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    Oh and good luck to everyone tomorrow I have got D1 at 9:30 and then this one straight afterwards. Biol and Chem 5 will probably decide my future
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    (Original post by TheUsername42)
    Hi could soon clear something up for me, in DNA sequencing, each test tube has DNA fragment + modified nucleotide + bank of nucleotides + radiotactive primer+ DNA polymerase.

    Surely the fact that the primer will have to attach to some bases at the beginning of the fragment means that when you read off the sequence on the electrophoresis gel you'll be reading from the last nucleotide on the primer - not the beginning of the DNA fragment?
    From the bottom up-
    A band corresponding to primer only - this is discounted (and you won't be shown this band in the exams)
    The first band of your sequence will correspond to (Primer)+(one base)
    The second of your sequence will correspond to (Primer)+(two bases)
    The third band of your sequence will correspond to (Primer)+(three bases)

    is that any more clearer?




    (Original post by kingsmod1)
    sorri guys but i do not understand why they use the sanger method and how that helps locate the bases they are lookin got, i mean if they didnt kno the bases they lookin for so then why are primers complemantary to it

    many thanks!!!! :P
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    (Original post by moniquesungirl)
    Anyone fancies to do a recap of chapter 16? For me is the hardest one :/
    ok so where to start right
    two ways to make dna fragments

    reverse transcriptase- is an enzyme converting mrna into dna
    useful because introns so can be used to transform bacteria only, which can then produce the proetins( bacteria cant slice)

    restriction endonucleases- these are made by bacteria to cut up viral dna
    they cut at recogntion sites which ususally have palindromic sequences
    sticky ends are produced because of the bases being revealed, and they are better than blunt ends as they are more specific
    restriction endonucleases can be used in vivo cloning to cut out a gene ( which has these recognition sites either side) and stuck into a plasmid cut once using the same restriction endonuclease

    these plasmids can used as vectors to insert into host cells
    note that if you want to transform a bacteria you usually use reverse transcriptase as well as restriction endonuclease but if you want to transform an animal or a plant you dont have to use reverse trancriptase becuase these organsims can splice out introns



    in vivo gene cloning clones directly and isnt done in living cells, you cant transform organisms in this way, as organisms are transformed through vivo cloning as the recombinant dna is replicated as part of their development





    in vitro is better as more dna is made in a shorter space of time, and also it doesnt need living cells so reduceds the need for growth mediums and culturing etc, but as its less specific it means that contaminant dna is also amplified,in addtion its less accurate because gene cloning for example conducts less errors, as its in living tissue so although mutations occur they are rare, while in vitro clonning isnt in lving tissue and so its artificial dna cloning and more errors are made


    gene therapy can treat cystic fibrosis as well as scid, by the use of adeno viruses, retrovirsues, or liposomes, and could either use somatic cell therapy or germ line therapy where germ line is negative because of the use of fertilised eggs and manipulating them , while its positive as it prevents immune reponses and is longer lived in that repeated treatement arent needed and isnt passed on to future regenerations. aduly Stem cells can also be used here, in somatic cell therapy, as they prevent repeated treatments being needed but it doesnt eliminate the fact that it is passed onto future geneartions..

    sequencing a gene
    sanger method/chain termination method
    restriction mapping- which aids sequencing as enables larger genes to be sequenced

    locating a gene- this is done after the sequencing method- using dna probes

    genetic screening and genetic fingerprinting both use dna probes
    in genetic screeing probes used to locate genes, in genetic fingerprinting porbes used to locate core sequences in introns which are at the same locations in all individuals but the number of times their repeated varies in each individual

    below is just a summary of where each of the different features are in different processes

    primers-
    pcr
    sanger method

    dna probes
    genetic fingerprinting
    restriction mapping
    locating a gene

    pcr
    genetic fingerprinting
    sanger method
    genetic scrreening- te replicate the probe
    in vitro cloning- it is invitro clongin

    hybridisation
    locating genes- dna probes
    genetic fingerprintin- dna probes


    restriction endonucleases-
    restriction mapping
    in viv gene cloning
    genetic fingerprintin
    used in gene therapy to cut out the gene etc and insert it as a vector-



    gel electrophoresis-
    dna fingerprining
    sequencing dna
    restrcion mapping
    locating a gene uv /xray
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    (Original post by Boo!xx)
    After you've used the single stranded DNA to a make the double strand in PCR do you use DNA helicase to seperate them, or just heat?

    Also how do you locate which gene is mutated?
    Probably heat, but I'm not sure.

    The location of the mutated gene is determined by the annealing of radioactive probes which can be seen by exposure of X ray film.
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    Can someone please help me with 10ci and ii? I know the answer, but don't understand how graph shows this? And what on earth does 'heat-killed' mean?

    http://store.aqa.org.uk/qual/gce/pdf...5-W-SQP-07.PDF QP

    http://store.aqa.org.uk/qual/gce/pdf...5-W-SMS-07.PDF MS
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    can anyone explain the difference between endotherms and ectotherms in terms of their activity and body temperature- can you relate it to metabolism etc??
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    (Original post by Tericon)
    Your diagram is fantastic, but I'm still a little confused...

    I get that 2 must be nearest the label as its the radioactive fragment, but its the partial digests that confuse me, they add up to more than 10? How can this be?

    How to find the fragment nearest the radioactive label is pretty much the only bit of RM i get
    ... That would be me getting a little copy and paste happy. Ignore the partial fragments at 3 and 5.
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    (Original post by appleschnapps)
    http://www.thestudentroom.co.uk/show...369&highlight=

    Er, hopefully simply enough?
    I'd rep you but I've run out of reps for today. Thank you!!!!
 
 
 
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