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    (Original post by Falcon91)
    Bravo, that was very good. Helped refresh my memory too :woo:


    1) IVF - An egg and sperm is harvested from two organisms of the same species (they can be chosen for certain desirable traits for farmers), the eggs taken are injected with the sperm to form the zygote. This is then grow in glasss tubes until an early embryo has formed. This is then planted into surrogate mothers and then can be born per norm.
    How is that cloning? The organism produced will not be identical to either of the parents.
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    (Original post by gma)
    How is that cloning? The organism produced will not be identical to either of the parents.
    After IVF, the embryo is split into a few parts that are then planted into surrogates. All the organisms will be genetically identical to each other, not to the parent.
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    Do we need to know the example on page 199 (succession)?
    Spec says describe one example of primary succession. Are they telling me that I have to memorise all of that utter rubbish?
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    (Original post by The TSR Star.)
    Do we need to know the example on page 199 (succession)?
    Spec says describe one example of primary succession. Are they telling me that I have to memorise all of that utter rubbish?

    My one example was Island of Surtsey. There's less info to remember than the sand dunes one.
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    Thanks again Falcon91! Trying to do some research on bp f to see if there's anything more substantial on it.

    Btw what book does everyone have? Mine really doesn't seem to correlate with the examples on here. I've got 'Cambridge University Press'.
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    (Original post by Falcon91)
    I get the same with this book, its completely ridiculous in some of the answers, im like yeah yeah i know it *checks back* oh FFS.

    Describe gel electrophoresis (were running out of questions :P)
    Exactly. Ask me a synoptic question for my next one, I haven't revised anything, but i'm curious to know if I remember it.

    Electrophoresis is a technique that is used to separate out fragments of DNA that are different lengths (and this is due to the use of varying restricion enzymes that cut the fragments at different sites on the DNA.
    The technique is extrememly accurate, even able to differentiate from bases that are only 1 nucleotide different in length.

    The DNA samples are placed in wells of agrarose gel where the negative electrode is placed. It is then immersed in a tank of buffer solution with electrodes connected at both ends, and a current is passed through it for a fixed period of time (around 2 hrs )
    As DNA is negativley charged due to its numerous phosphate groups it will move towards the negative electrode. Different lengths strands will move different distances because they will be held up more/less within the agrarose gel slab that is used.
    The DNA can be marked to show their position. They can be transferred onto paper/other materials for further analysis, this technique is called southern blotting. A nitrocellulose/nylon sheet is used. The position of the DNA strands can be seen by used of radiocative marked samples, which show up under photographic film, or if marked by flurescence so they show up under UV light. Alternatively if you wish to locate a specific base sequence/gene such as for the use of genetic engineering you can use a DNA probe which is a short single stranded piece of DNA 50-80 nucleotides long, and this will anneal to the required gene in the sample and show up under the photographic film.

    How do you keep up supply of ATP for muscle contraction?

    Hope this works...
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    (Original post by The TSR Star.)
    Do we need to know the example on page 199 (succession)?
    Spec says describe one example of primary succession. Are they telling me that I have to memorise all of that utter rubbish?
    I've learnt Glacier Bay in Alaska, its pretty simple tbh. Here are my notes:

    Succession in Glacier Bay, Alaska
    --> directional change in a community over time

    1. Glacier retreats, exposing bare moraine
    Rate and extent of retreat increases due to global warming

    2. Pioneer plants colonise the moraine, altering the soil composition
    Grow sparsely in non-existent soil; mosses, willow-herbs, mountain avens & dwarf willows. Mountain avens outcompete other plants due to mutalistic relationship with Rhizobium.

    3. pH of soil decreases & shrubs outcompete pioneers for light now there’s thin, more fertile soil
    Proper soil forms, containing humus (acidic due to alders’ decay), which is able to hold NH4+ & mineral ions, enabling shrubs e.g. alders to grow.

    4. Tall conifer trees crowd alders --> climax community if drainage is good
    e.g. hemlock and sitka spruce (not N-fixers therefore depend on N in soil)

    5. Poor drainage : sphagnum bog develops
    pH is lowered due to mosses holding H2O & [O2] decreases, killing trees

    Abiotic factors, e.g. [nutrients] in soil & H2O availability are important in the early stages of succession, whereas when more species colonise, biotic factors e.g. competition are important.
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    in relation to the post 2 above here!
    Spoiler:
    Show


    maintenance of ATP supply for muscle contraction in 3 main ways:

    Aerobic respiration, in mitochondria, via oxidative phosphorylation. needs oxygen
    Anaerobic respiration, in cytoplasm, via glycolysis. this produces pyruvate (which becomes lactate in lactate fermentation - build up of lactate causes muscle fatigue - quickly)
    or via the PCr system - also known as ATP-phosphocreatine system, in which ATP is made by phosphorylating ADP (adding a phosphate group) taken from phosphocreatine). The ATP-PCr system is anaerobic (no oxygen required) and produces no lactate - but only works for a few seconds. uses the enzyme creatine phosphotransferase

    Reasons you need ATP in muscle contraction

    protein synthesis
    contraction of sarcomeres in powerstroke
    regeneration of creatine-phosphate when muscle is resting
    to actively transport calcium ions out of sarcoplasm and back into sarcoplasmic recticulum, via transporter proteins




    can someone help me out with page 130 (what determines sex) of Sue Hocking's OCR book please? Stretch + challenge question B - the answer provided at back of book makes no sense! the question says 'her female offspring are black', yet the answer seems to imply they are white / normal?
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    quick questions..
    why with DNA probes do you need to transfer the fragments onto a nylon membrane?
    why cant the probe be added to the agarose gel in the electrophoresis..?


    EDIT: i dont actually know the answers - this is a genuine question!! lol :s
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    (Original post by ViolinGirl)
    Exactly. Ask me a synoptic question for my next one, I haven't revised anything, but i'm curious to know if I remember it.

    How do you keep up supply of ATP for muscle contraction?
    Hope this works...
    LOL @ the image :woo: I believe that one is called Gerbil Gerbil (taking from the inspirational name, Gorilla Gorilla)


    ATP Supply for muscular contraction

    1) Aerobic Resp - Produces many ATP via oxidative phosphorylation, also goes through glycolysis, link + krebs cycle which generate products to be used during Oxidative phos. Happens in the mitochondrion of a muscle fibre on the inner membrane/cristae. Produces many ATP fairly slowly so is used for low intensity exercise such as walking. Depends on the amount of respiratory substrate (glucose) available and on the blood supply to provide oxygen which is the final electron acceptor in the ETC which forms water.

    2) Anaerobic Resp - Produces a few ATP rapidly, without the presence of oxygen, glycolysis takes place in the sarcoplasm of a muscle fibre and then produces lactate. However lactate is toxic, builds up and causes muscle fatigue, its carried away in the blood in which pH is kept constant by buffers, however it stimulates increased blood flow to the muscle fibre. Used for high intensity exercise such as sprinting.

    3) ATP-PCr system - produces ATP from ADP by donating its phosphate group to ADP using the enzyme creatine phosphotransferase in the sarcoplasm of a muscle fibre, this is very rapid. However only a small amount of PCr stored in cells so can only provide energy for contraction for about 2-4 seconds. Its alactic and anaerobic (no oxygen needed and no lactate produced). Used for short bursts of vigorous exercise such as a tennis serve.

    ATP is needed for active transp of Ca2+ ions back into sarco-reticulum, contraction of muscle fibre during power stroke, also needed to break actin-myosin cross bridge.

    Explain how atherosclerosis occurs, referring to the build up of atheromas :eek:
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    (Original post by Archen)
    quick questions..
    why with DNA probes do you need to transfer the fragments onto a nylon membrane?
    why cant the probe be added to the agarose gel in the electrophoresis..?


    EDIT: i dont actually know the answers - this is a genuine question!! lol :s

    This is by no means a definite answer, but perhaps because once you add the probe (being a short strand of DNA in effect) it would become 'sorted' in part of the electrophoresis process. As in, it has a negative charge, so instead of binding to any complementary sequence (which would require mixing and a collision between probe + DNA sequence), it is attracted to positive anode and moves along the agarose gel, so it doesn't 'hit' any complementary sequence. If that makes sense?:P
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    (Original post by mikey_g)
    in relation to the post 2 above here!
    Spoiler:
    Show


    maintenance of ATP supply for muscle contraction in 3 main ways:

    Aerobic respiration, in mitochondria, via oxidative phosphorylation. needs oxygen
    Anaerobic respiration, in cytoplasm, via glycolysis. this produces pyruvate (which becomes lactate in lactate fermentation - build up of lactate causes muscle fatigue - quickly)
    or via the PCr system - also known as ATP-phosphocreatine system, in which ATP is made by phosphorylating ADP (adding a phosphate group) taken from phosphocreatine). The ATP-PCr system is anaerobic (no oxygen required) and produces no lactate - but only works for a few seconds. uses the enzyme creatine phosphotransferase

    Reasons you need ATP in muscle contraction

    protein synthesis
    contraction of sarcomeres in powerstroke
    regeneration of creatine-phosphate when muscle is resting
    to actively transport calcium ions out of sarcoplasm and back into sarcoplasmic recticulum, via transporter proteins




    can someone help me out with page 130 (what determines sex) of Sue Hocking's OCR book please? Stretch + challenge question B - the answer provided at back of book makes no sense! the question says 'her female offspring are black', yet the answer seems to imply they are white / normal?
    Yo yo the answers are wrong for most of the questions, i had a massive argument avec my teacher and i was right in the end. Basically, ignore that whole double spread - both the answers and questions are incorrect.

    That should make you smile hopefully - nothing like being convinced your right and told your wrong.

    P.s I see your a fellow to-be cambridge person!
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    (Original post by radical07)
    Yo yo the answers are wrong for most of the questions, i had a massive argument avec my teacher and i was right in the end. Basically, ignore that whole double spread - both the answers and questions are incorrect.

    That should make you smile hopefully - nothing like being convinced your right and told your wrong.

    P.s I see your a fellow to-be cambridge person!
    Yo yo yo yo, its not on the spec :holmes:
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    Hey again The link from the first post gives some past paper questions, but just wondering if there is a full pack of all the questions from different topics or a website link with all the relevant past papers? Thanks for any help
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    (Original post by Archen)
    abscisic acid (ABA)
    closure of stomata/ stress hormone which prevents excess water loss
    inhibiting of protein pump

    abscission of leaves/fruits

    promotes seed dormancy/ inhibits germination
    prevents production of enzymes


    this is taken from the mark scheme of the central concepts jan 2005 paper
    the question was just to name two plant hormones and their effects
    this is what the mark scheme said for abscisic acid
    hope this helps
    Ahh I see, so I guess you'd get a mark for putting abscission of leaves even if nobody knows :yep:
    Thanks!
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    (Original post by ibysaiyan)
    need to focus on maths and my f212 module. =} I will be back I promise
    let me guess, F212 on Tuesday morning and S2 on Wednesday afternoon lol

    i finally finished f212 by only revising the stuff i think will come up
    I'll be doing some s2 work tomorrow(not much apart from doing past paper as i have finished every chapter of s2 lol took me ages) then maybe do some c4 and G485 lol these two major units on same day(18th june) lol :yikes:
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    (Original post by Remarqable M)
    let me guess, F212 on Tuesday morning and S2 on Wednesday afternoon lol

    i finally finished f212 by only revising the stuff i think will come up
    I'll be doing some s2 work tomorrow(not much apart from doing past paper as i have finished every chapter of s2 lol took me ages) then maybe do some c4 and G485 lol these two major units on same day(18th june) lol :yikes:
    LOL and thats not only it ... then comes 15th c4,16th f215,`8th ph4,and two more!!!
    anyways yea I will sleep now (early) gonna get up at 3.30ish AM to revise f212. It should be alright now seeing much of f215 parallels with f212 eco. stuff
    Good luck =)
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    (Original post by TheMikester69)
    Ahh I see, so I guess you'd get a mark for putting abscission of leaves even if nobody knows :yep:
    Thanks!
    im sure i read somewhere in the book saying a recent research has showing that abscisic acid has nothing to do with abscission of leaves
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    (Original post by ibysaiyan)
    LOL and thats not only it ... then comes 15th c4,16th f215,`8th ph4,and two more!!!
    anyways yea I will sleep now (early) gonna get up at 3.30ish AM to revise f212. It should be alright now seeing much of f215 parallels with f212 eco. stuff
    Good luck =)
    Good luck to you too:p: i'm sure you''ll ace them all because you're one hell of a smart guy lol
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    (Original post by Remarqable M)
    Good luck to you too:p: i'm sure you''ll ace them all because you're one hell of a smart guy lol
    Ameen bro. and you too. Now time I sleep
    c you around f215 and 214
 
 
 
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