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Edexcel B3 unofficial markscheme 19th June 2017 Watch

  • View Poll Results: What mark do you think you got?
    55+
    23
    8.61%
    47-54
    98
    36.70%
    39-46
    88
    32.96%
    30-38
    41
    15.36%
    22-29
    12
    4.49%
    Under 22
    5
    1.87%

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    And it was 25% the Punnett square is referencing all genders, not just the male. You had to interpret the q as 'what's the chance of the offspring being a male with haemophilia' so u have to consider all 4 options
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    (Original post by stephen1011)
    50% is the correct answer, as we are assuming that the sex was male, the chance of inheritence is 50% rather than 25%.
    The question was about the probability of the offsprings who inherit the disease. Not the probability of getting male offsprings. Also the diease is found on the X chromosome not Y.

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    I wouldn't be surprised if both 48 and 24 are accepted, the question was not the best worded.
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    (Original post by Zainyg)
    what was the 3 mark calculation?
    The answer was 24
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    (Original post by jashab14)
    Everyone in my school got 24 but to be honest, they didn't make it clear as to whether the 0.925% and 0.625% was of the entire 16,000 or out of the two 8,000 groups
    IF you read the top of the question it said two groups of 16,000 split equally this means 8,000 each
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    (Original post by Aaron jhooty)
    I wouldn't be surprised if both 48 and 24 are accepted, the question was not the best worded.
    It was 24, you'll get 2/3 for putting 48, but the question clearly stated the groups were split into two.
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    (Original post by Olivia2442)
    What did people get for the punnett square question?
    I originally got 25% but it said the chance of having a 'boy with haemophilia' which was 50%. One boy with no traces of it and one boy with it.
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    (Original post by Schoolstudent01)
    I got 48 people

    I used the total to work out the percentage of the total and got 100 or one and 148 for the other. 148-100= 48

    Did anyone else do this?
    exactly what I did, pretty sure its right as the numbers work well.
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    (Original post by dd897)
    Here is the long awaited markscheme. I think the grade boundaries will be pretty low but overall I think personally I did okay – Please remember you can bring up your grade with the other exams and don’t worry if you get wrong answers! Feel free to add to the markscheme below as I can’t remember all the questions. Good luck!

    1a. Species 1 because the nectar is at the top

    1b. Option D

    1c. Co-evolution: As one species evolves the other devolves so moth becomes deformed so its proboscis shrinks so co-evolution benefits the orchid, not the moth

    2a. Dominant allele = Male Recessive allele = Female OR Isotope monitor

    Classical conditioning

    Put a flag in front of horse to habituate it

    38 HIV

    Vegetarian cheese à use restriction enzyme to combine milk together to make it yellow and clot to form cheese and then put it into a fermenter

    Lactose free-milk à Normal milk + sieve + barium nitrate, so lactose is extracted. Include conditions of pH, temperature and contamination
    Nice troll mark scheme
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    I Got 240 because I divided wrong . Do you reckon I will still get 2 out of the 3 marks?
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    Its 24 because if you do do it over 16000, it wont make sense as it clearly states its divided into separate groups
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    Guys i got the multiplication wrong at got 240 instead of 24 do you reckon I will still get 2 out of 3 marks
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    (Original post by Ganesh Nair)
    are you sure because I put 25%, others are saying 50%
    i'm sure
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    (Original post by dd897)
    Here is the long awaited markscheme. I think the grade boundaries will be pretty low but overall I think personally I did okay – Please remember you can bring up your grade with the other exams and don’t worry if you get wrong answers! Feel free to add to the markscheme below as I can’t remember all the questions. Good luck!

    1a. Species 1 because the nectar is at the top

    1b. Option D

    1c. Co-evolution: As one species evolves the other devolves so moth becomes deformed so its proboscis shrinks so co-evolution benefits the orchid, not the moth

    2a. Dominant allele = Male Recessive allele = Female OR Isotope monitor

    Classical conditioning

    Put a flag in front of horse to habituate it

    38 HIV

    Vegetarian cheese à use restriction enzyme to combine milk together to make it yellow and clot to form cheese and then put it into a fermenter

    Lactose free-milk à Normal milk + sieve + barium nitrate, so lactose is extracted. Include conditions of pH, temperature and contamination
    This is a joke right?
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    (Original post by agi2)
    its 50% because it was only to do with the male not male and female
    i put 25% though :/
    It is 25%, you want the chance of having a male with the disease, there are 4 possibilities having a girl is still a possibility you don't assume the offspring is a boy, this has never been the case with GCSE punnet square questions.
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    (Original post by Yateschloe00)
    I originally got 25% but it said the chance of having a 'boy with haemophilia' which was 50%. One boy with no traces of it and one boy with it.
    You still have the possibility of having a girl, the question asked for a boy with the disease, as a result it is out of all possibilities which is 25%. You can't assume it will be a boy. You can check past papers, you never calculate chances out of two possibilities when there are 4 unless stated, which it didn't.
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    (Original post by stephen1011)
    mate, it says the expirement is split in half between 16000 people; so its 8000 each.
    Damn I didn't see that part, ive failed so bad
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    What did you guys say about the butterflies laying eggs under the leaves???
    • Thread Starter
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    (Original post by RHIgnis)
    What did you guys say about the butterflies laying eggs under the leaves???
    Less predators will soot the eggs and so it is less likely to be eaten thus increasing its chance of survival
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    What did u guys put for the transgenic question, I said:
    Restriction enzyme
    Ligases enzyme
    Sticky ends
    Vector
    Infects plant so DNA incorporated into plant
    I also mentioned crown galls
 
 
 
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