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    (Original post by yesioo)
    Can someone explain epistasis? Meiosis and Variation is my weakest topic and I've got a horrible feeling it's going to be worth big marks.
    Epistasis is the masking of a gene to express another. I suggest youtube as I can't explain it really on here.
    For example if you have the genotype AaBb, AND we say that A is dominant to bb, then when we have A_ _ _ it wont matter what we have in the remaining 3. I don't know if I explained that properly tbh.
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    (Original post by J DOT A)
    Guys, whats the difference between Primary and secondary metabolites.... and why is it that the production of primary metabolites is nearly nsync with the population growth of microorganism in a closed culture?
    Primary metabolites are those that are produced as part of an organisms normal growth. It usually occur's in the Log/exponential phase due to the fact there is unlimited growth substances i.e. no limiting factors.

    Whereas, secondary metabolites are those that are produced which are not part of the normal growth of an organisms such as penicillin. It occurs in stationary phase where the culture is described as being "under pressure" hence these substances are produced. They are usually produced after the main growth-exponential-phase.

    And well for the last question I think the definition answers it. Its because primary metabolites are part of normal growth and therefore they grow at the same rate as microrganisms are being reproduced via binary fission due to the unlimited resources.

    Hope this helps a bit.
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    (Original post by slacker07906)
    Primary metabolites are those that are produced as part of an organisms normal growth. It usually occur's in the Log/exponential phase due to the fact there is unlimited growth substances i.e. no limiting factors.

    Whereas, secondary metabolites are those that are produced which are not part of the normal growth of an organisms such as penicillin. It occurs in stationary phase where the culture is described as being "under pressure" hence these substances are produced. They are usually produced after the main growth-exponential-phase.

    And well for the last question I think the definition answers it. Its because primary metabolites are part of normal growth and therefore they grow at the same rate as microrganisms are being reproduced via binary fission due to the unlimited resources.

    Hope this helps a bit.
    Oh so they are reproducing asexually so of course it will be Binary fission! Thanks for that, really helped
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    do we have to know details on the drosophila fruit fly?
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    plus do you guys actually read the HOW SCIENCE WORKS (green pages)?
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    (Original post by Viva009)
    do we have to know details on the drosophila fruit fly?
    No not on syllabus.
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    I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

    What does everyone think?
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    I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

    What does everyone think?
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    (Original post by LisaWilliams)
    I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

    What does everyone think?
    I'm also thinking an essay on Meiosis and it's significance in variation from the first module. Possibly something to do with Apoptosis?
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    I'm just about to have a look through the past papers/specification and see what hasn't been asked yet, but im thinking maybe nitrogen cycle? and probably meiosis too
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    (Original post by LisaWilliams)
    I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

    What does everyone think?
    also, i doubt there'll be a proteinsynthesis essay as there was one in june 2010, i believee
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    Guys how would you answer question 3 of this paper?
    FIXED http://pastpapers.org/A2/biology/cen...20Jan%20QP.pdf
    Woops sorry about that..although it looks like it's a bit more about the old syllabus
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    (Original post by tesha_al)
    Guys how would you answer question 3 of this paper?
    http://moodle01.st-davids-coll.ac.uk...06%20paper.pdf
    we need to log in to look at the paper
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    (Original post by katie93)
    we need to log in to look at the paper
    fixed
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    I can't do hardy weinberg!!! LOL. Might spend an all day on it tomorrow. And as for meiosis and how it contributes to variation is crossin over, random distribution of chromosomes and random distribution of chromatids right?

    Also, my teacher predicted the following things-

    1. Meiosis- essay
    2. Hardy weinberg
    3. Succession- particularly deflected.
    4, Galapagos islands
    5. Nitrogen cycle
    6. The movement of muscles-antagonistic
    7.Cycle of muscle contraction
    8. Electrophoresis
    9, Somatic gene therapy.
    10. Coppicing

    Arghhhhh least I only need a D in this exam!
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    (Original post by tesha_al)
    Guys how would you answer question 3 of this paper?
    FIXED http://pastpapers.org/A2/biology/cen...20Jan%20QP.pdf
    Woops sorry about that..although it looks like it's a bit more about the old syllabus
    Yeah it is the old syllabus, but heres how i'd answer it anyway
    3)a)i) A, B, E
    ii) Females in stage A are diploid, and formed from the gametes of 2 random fleas mating, A females are more likely to contain a wider variety of alleles than those in stage D.
    iii) C and D are both haploid, so mitosis will produce more haploid gametes (with same number of chromosomes)
    b) In prophase 1, bivalents form between homologues. This leads to the formation of chiasmata and crossing over between maternal and paternal alleles occurs (exchanging of alleles) forming varied chromosomes. In metaphase I bivalents align randomly at the equator, so random assortment occurs and resulting cells may have any combination of maternal and paternal chromosomes. In metaphase II chromosomes align randomly on the equator, so random assortment occurs and resulting cells may have any combination of maternal/paternal chromatids
    c) Parental genotypes: IoIo x IoIo, IaIb x IoIo, IaIa x IoIo, IaIb x IaIa
    Baby blood group: O, B, A, AB

    heres the mark scheme too: http://pastpapers.org/A2/biology/cen...20Jan%20MS.pdf
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    hopefully this will be useful to people struggling to get past paper questions together. my teacher made this up, basically just goes through every past paper from the old course and says what topic it's on, the trick is finding the paper online, paperbank has most of them though!
    also does anybody know how the mark schemes will differ on the old papers compared to the new?

    hope this is useful!
    Attached Files
  1. File Type: xlsx Past_Question_Database.xlsx (17.9 KB, 161 views)
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    (Original post by katie93)
    Yeah it is the old syllabus, but heres how i'd answer it anyway
    3)a)i) A, B, E
    ii) Females in stage A are diploid, and formed from the gametes of 2 random fleas mating, A females are more likely to contain a wider variety of alleles than those in stage D.
    iii) C and D are both haploid, so mitosis will produce more haploid gametes (with same number of chromosomes)
    b) In prophase 1, bivalents form between homologues. This leads to the formation of chiasmata and crossing over between maternal and paternal alleles occurs (exchanging of alleles) forming varied chromosomes. In metaphase I bivalents align randomly at the equator, so random assortment occurs and resulting cells may have any combination of maternal and paternal chromosomes. In metaphase II chromosomes align randomly on the equator, so random assortment occurs and resulting cells may have any combination of maternal/paternal chromatids
    c) Parental genotypes: IoIo x IoIo, IaIb x IoIo, IaIa x IoIo, IaIb x IaIa
    Baby blood group: O, B, A, AB

    heres the mark scheme too: http://pastpapers.org/A2/biology/cen...20Jan%20MS.pdf
    thanks yeah I looked at mark scheme and it was pretty vague but if its old syllabus then its fine!
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    ..........
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    little suprise
    Attached Files
  2. File Type: rtf Cellular control questions F215.rtf (1.18 MB, 121 views)
  3. File Type: rtf Cellular control answers F215.rtf (220.5 KB, 87 views)
  4. File Type: rtf Ecosystems and sustainability questions F215 part 1.rtf (1,019.5 KB, 175 views)
  5. File Type: rtf Ecosystems and sustainability questions F215 part 2.rtf (716.2 KB, 105 views)
  6. File Type: rtf Ecosystems and sustainability questions F215 part 3.rtf (754.2 KB, 82 views)
  7. File Type: rtf Ecosystems and sustainability answers F215.rtf (81.0 KB, 73 views)
 
 
 
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