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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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    A gene is a section of DNA that codes for a single polypeptide
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    (Original post by Introverted moron)
    It was on a test that we did in class last year. The exact question was:

    3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

    ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

    b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

    I don't get this one either. Why do bacteria produce substances that could kill them? :confused:
    This is blowing my mind. just 4gt it, it just should not come in the paper...
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    (Original post by Introverted moron)
    It was on a test that we did in class last year. The exact question was:

    3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

    ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

    b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

    I don't get this one either. Why do bacteria produce substances that could kill them? :confused:

    (Original post by therapist_1)
    This is blowing my mind. just 4gt it, it just should not come in the paper...

    ai) I think antibodies inhibit the enzyme that makes the cell wall so it becomes weaker so it bursts from osmotic lysis. Viruses are strands of DNA so antibiotics won't work as it has no wall.
    aii)The virus may infect a cell so the infected cell must be destroyed to erradicate the virus?
    b)They reproduce rapidly to higher yield?

    The bacteria don't produce substance that could kill them. Scientists genetically engineer them by putting the strand that codes for it in the plasmid. When it replicates, the daughter cells contain the gene to code for it too.
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    Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

    I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?
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    (Original post by Introverted moron)
    It was on a test that we did in class last year. The exact question was:

    3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

    ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

    b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

    I don't get this one either. Why do bacteria produce substances that could kill them? :confused:
    Hmmm, in regards to 3a) ii), on page 224 of the Nelson Thornes textbook it says:

    "Antibiotics are sometimes used to treat viral diseases because although they are ineffective against viruses, they may help to prevent the development of secondary bacterial infections to which patients may be vulnerable."

    I hope that's all they want you to say otherwise I have no idea.
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    (Original post by SittingOnCornflakes)
    Hmmm, in regards to 3a) ii), on page 224 of the Nelson Thornes textbook it says:

    "Antibiotics are sometimes used to treat viral diseases because although they are ineffective against viruses, they may help to prevent the development of secondary bacterial infections to which patients may be vulnerable."

    I hope that's all they want you to say otherwise I have no idea.
    That should be it thanks:cool:
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    Dreading this exam
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    (Original post by lolo-x)
    Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

    I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?
    start and a stop code
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    (Original post by lolo-x)
    Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

    I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?
    Inclusion of start and stop codons in the DNA base sequence. As a gene is [Start Codon][Gene][Stop Codon]
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    Silly question (I know) but I need to be sure...

    We dont have to learn what MRSA stands for do we?
    Just the example of the whole antibacterial resistance thingy, right?
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    (Original post by TlanTlan)
    Inclusion of start and stop codons in the DNA base sequence. As a gene is [Start Codon][Gene][Stop Codon]
    oh my god i have no idea what a start or stop codon is
    so how come that makes it 384 or 387 as well? surely that would make it 383 :/
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    (Original post by spoinkytheduck)
    Silly question (I know) but I need to be sure...

    We dont have to learn what MRSA stands for do we?
    Just the example of the whole antibacterial resistance thingy, right?
    no we don't specification says "Antibiotic resistance in terms of the difficulty of treating tuberculosis and MRSA"
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    (Original post by lolo-x)
    oh my god i have no idea what a start or stop codon is
    so how come that makes it 384 or 387 as well? surely that would make it 383 :/
    The stop and start codons are worth 3 bases each

    so 381 + 3 or 6 = 384 or 387
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    (Original post by spoinkytheduck)
    The stop and start codons are worth 3 bases each

    so 381 + 3 or 6 = 384 or 387
    ok, thank you, so do all genes have start and stop codons? wouldn't you always add 6 then?
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    (Original post by lolo-x)
    no we don't specification says "Antibiotic resistance in terms of the difficulty of treating tuberculosis and MRSA"
    Good-o
    I didnt fancy learning the extra long complicated words...

    Haha, I answered your question as you answered mine!
    (well I hope I answered it!)


    (Original post by lolo-x)
    ok, thank you, so do all genes have start and stop codons? wouldn't you always add 6 then?
    Uuumm... dont know about that, I think different people are taught slightly different things so that why the mark scheme you were looking at allowed 3 different answers.
    Just stick to the way you are doing it and it should be fine
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    (Original post by spoinkytheduck)
    Good-o
    I didnt fancy learning the extra long complicated words...

    Haha, I answered your question as you answered mine!
    (well I hope I answered it!)



    Uuumm... dont know about that, I think different people are taught slightly different things so that why the mark scheme you were looking at allowed 3 different answers.
    Just stick to the way you are doing it and it should be fine
    no, me neither lol i've lost the will to live a bit revision wise, i've decided to make notes using the specification now.. probably should have done that already haha

    ah good, thank you good luck on thursday!
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    Just about to begin to teach myself the whole of unit 2 as I hate this subject... wish me luck.
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    (Original post by lolo-x)
    no, me neither lol i've lost the will to live a bit revision wise, i've decided to make notes using the specification now.. probably should have done that already haha

    ah good, thank you good luck on thursday!
    Same.. kind of looking forward to the exam in a weird way (just so the intense revision will be over!! )

    Haha, I havent even made notes from the spec! My bad...
    Just going through the textbook hoping something goes in!

    Good luck for Thursday too!
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    (Original post by spoinkytheduck)
    Same.. kind of looking forward to the exam in a weird way (just so the intense revision will be over!! )

    Haha, I havent even made notes from the spec! My bad...
    Just going through the textbook hoping something goes in!

    Good luck for Thursday too!

    i am too lol
    oh i wouldn't worry if you have a textbook haha, i don't have one though so thought i'd best get some structure to my revision going, i don't want anything filling up my head that we don't actually need to know!
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    Worried about this, was confident on the last one for an A and ended up with a B. By no means bad, but I really want that A, does anyone have any predictions on what's going to come up?
 
 
 
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