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    Hi, Can you send me a link to your notes then please when you can? Thanks
    (Original post by AortaStudyMore)
    argh! I would love to but I'm behind on my uni notes haha, and as I said to someone else, I do need to prioritise my university studies :P I am however going home tonight for the weekend, if you remind me tomorrow, I can send you my notes on the topics, they're old spec, but not too much should have changed I expect
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    (Original post by AortaStudyMore)
    I don't really know how much detail you want, so if there's anything you still don't understand in this brief overview, then just ask me. Also my DNA tech knowledge might be a tad rusty! So restriction mapping involves using restriction endonucleases to cleave DNA at specific recognition sites, such examples would be EcoRI (which is an enzyme released by E. coli I believe) and HindIII. Once you have your DNA fragments, you separate them by gel electrophoresis, basically, smaller fragments travel through the gel quicker than larger fragments, so smaller fragments will be further from the point of origin than larger fragments. They often ask questions that require you to determine how many recognition sites there were in a length of DNA, this is quite tricky, and I don't think I can really explain it here without diagrams and stuff, so you will be better off asking a teacher about that, although I do have notes that explain it pretty well if you'd like me to send them to you.

    As for gene therapy, there are 2 types, somatic cell and germ-line. Germ-line is outright illegal. Germ-line cells are the cells found in the testes and ovaries that will divide by meiosis to form the gametes, any DNA changes in these cells is heritable, unlike somatic cells (body cells, i.e. every other cell that isn't a germ cell). I don't know the legal status of somatic cell gene therapy, but the theory behind it essentially involves infecting cells with a virus. So a virus is basically just genetic material inside a shell, and they have what is called "tropism" (don't worry about this), but what this means is specific viruses have a tendency to infect certain tissues and not others. For example, influenza viruses only infect respiratory epithelia, because the necessary enzymes needed to allow the virus to release its genetic material inside the cell are only found in the upper respiratory tract. This is pretty handy, because it means you can load viruses with a healthy version of a gene and "infect" the patient. The virus will only infect the target tissue (because of their tropism) and release the healthy gene into cell. The key thing to remember here is that the healthy gene does not replace the unhealthy gene, it just masks the unhealthy gene's effects. So when you do gene therapy, the healthy gene you're putting into the cells must be dominant to the unhealthy gene. But because the unhealthy gene is not replaced, it means that the healthy gene is not conserved in mitosis, which means that somatic cell gene therapy requires constant treatment, because the effects of the therapy don't last long. I can't remember the specifics, you'll need the textbook for that, but as far as I remember, the 2 ways of getting the DNA inside the body were adenoviruses and liposomes, and they each had their advantages and disadvantages (like the use of adenoviruses carried a risk of actual infection, that sort of thing!).

    Finally, regulation of gene expression. This is an interesting topic, genes can be regulated in 2 ways, you can regulate how much mRNA is made, and you can regulate how much mRNA is used to make protein. So the first way involves transcription factors. These are usually found either already bound to DNA or in the cytoplasm. The thing to remember here is that there is always some transcription going on in a gene, transcription factors just regulate the level at which that basic level of transcription is happening. So what happens, is a signal comes a long and activates the TF, the TF then binds to a site close to the gene on DNA, the DNA then loops around so that the TF comes close to the gene promoter region (a sequence of bases containing A's and T's) which is where RNA polymerase binds. The TF can then either upregulate or downregulate the binding of RNA polymerase, and hence the level of transcription. The second way genes are regulated is by RNA interference. This basically involves inactivation of the mRNA that has been formed from transcription. Now it gets a bit complicated, as the way your body does this is by producing microRNA, but we'll just focus on siRNA, as that's what you need for A-level. So siRNA is formed from fragments of double stranded RNA. The dsRNA is cut into smaller pieces, and then the strands are separated into single strands. The single strands are loaded onto a complex of enzymes, and because the single strands are complementary to the original RNA, they bind to the RNA, once bound, the enzymes cut up the RNA and hence it cannot be used to make any protein. This is a common viral defense mechanism, as I said before, our cells actually make what is called miRNA, which does the same thing as siRNA, but it binds to our mRNA instead and cuts it into smaller pieces, thus silencing gene expression. I feel like I've complicated this more than necessary though, so just remember that siRNAs are small lengths of RNA that are complementary to RNA that is going to go and make a protein. Because the siRNA is complementary to the mRNA, it binds to it, the siRNA is also bound to an enzyme complex, which chops up the mRNA, thus preventing it from making protein
    YOU ARE AMAZING!!! That was so helpful! You didn't over complicate it as that's the level of detail we'd reached, just the microRNA but I'm trying to learn things that are not on the specification too as the essay question at the end of one of the papers awards marks for, what they say, "goes above and beyond what is expected of an A-level student and what is on the spec". Really helpful actually, your notes on restriction mapping would be great, but if you're busy don't worry. Thank you SO much!!
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    (Original post by charlieecooperr)
    YOU ARE AMAZING!!! That was so helpful! You didn't over complicate it as that's the level of detail we'd reached, just the microRNA but I'm trying to learn things that are not on the specification too as the essay question at the end of one of the papers awards marks for, what they say, "goes above and beyond what is expected of an A-level student and what is on the spec". Really helpful actually, your notes on restriction mapping would be great, but if you're busy don't worry. Thank you SO much!!
    How'd you like me to send them to you?
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    (Original post by AortaStudyMore)
    How'd you like me to send them to you?
    Howevers easiest, either DM me on here or I can give you my email?
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    Is NH4+ a strong acid or a weak one?
    As in it is conjugate acid of a weak base so should be a strong acid but at the same time, it doesn't dissociate competely so should be weak acid i guess?:confused::argh::banghead:
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    (Original post by Aimen.)
    Is NH4+ a strong acid or a weak one?
    As in it is conjugate acid of a weak base so should be a strong acid but at the same time, it doesn't dissociate competely so should be weak acid i guess?:confused::argh::banghead:
    It's weak, you did kind of answer that yourself :P If it only partially dissociates then it is weak by definition
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    (Original post by AortaStudyMore)
    How'd you like me to send them to you?
    Hello! I'll be doing my EMPA exams soon (I'm on AQA for Biology!) I was just wondering what tips you might give to revise for Task 3? Also, if it isn't a hassle, could you please also send me the notes on Biology as I'm struggling so much and need to get an A this year to make it to uni! Thank you ever so much!!
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    (Original post by AortaStudyMore)
    It's weak, you did kind of answer that yourself :P If it only partially dissociates then it is weak by definition
    But aren't conjugate acids of weak bases, strong acids? :confused:
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    (Original post by 15demon)
    I have my iGCSE Bio Atp exam tomorrow. I want to know what exactly is it that I need to study for it and where do I find it.
    Yh sure, so you need to know 6 stages of the cardiac cycle, some rather complicated flow-volume loop interpretations, the hypothalamo-adenohypophysial axis, the difference between white and gray matter, oh and of course the 3 types of subcutaneous mycoses.

    In terms of where you'll find it, I expect the paper will be on your desk!

    Good luck
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    (Original post by jaseho98)
    Hello! I'll be doing my EMPA exams soon (I'm on AQA for Biology!) I was just wondering what tips you might give to revise for Task 3? Also, if it isn't a hassle, could you please also send me the notes on Biology as I'm struggling so much and need to get an A this year to make it to uni! Thank you ever so much!!
    There isn't really much you can do, just make sure you know the content that you were told to revise, they usually only ask like a 1 or 2 mark questions on it, but it might help with the other questions. You could also predict some of the things they may ask, me and a friend did that last year, and then made mark scheme answers for our predicted questions, and a fair few came up, so that helps, but it depends if you can be bothered to do that. You could also do past papers if they help, I didn't find them useful though. Sorry there isn't much advice I can give, EMPAs are horrible, but they're not worth much, and boundaries are usually low, so they're not be all and end all!

    And yh sure, how'd you like me to send them to you? I only have my biol 5 ones on me at uni though I'm afraid
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    (Original post by Aimen.)
    But aren't conjugate acids of weak bases, strong acids? :confused:
    What's your logic behind that? :P I've never come across the concept before, but if you remember the main strong acids (HCl, H2SO4, H3PO4) then it will be a pretty safe bet that any others are weak. Don't get bogged down in this, unless you need to for your course? Even I didn't really ever come across this, and I did a lot of random research during my A-levels haha
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    (Original post by AortaStudyMore)
    There isn't really much you can do, just make sure you know the content that you were told to revise, they usually only ask like a 1 or 2 mark questions on it, but it might help with the other questions. You could also predict some of the things they may ask, me and a friend did that last year, and then made mark scheme answers for our predicted questions, and a fair few came up, so that helps, but it depends if you can be bothered to do that. You could also do past papers if they help, I didn't find them useful though. Sorry there isn't much advice I can give, EMPAs are horrible, but they're not worth much, and boundaries are usually low, so they're not be all and end all!

    And yh sure, how'd you like me to send them to you? I only have my biol 5 ones on me at uni though I'm afraid
    Thank you so much! I do hate EMPAs so so so much! If possible, can you email it to my email address please? (I will DM you ) x
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    (Original post by 15demon)
    Are you talking about Premedical or iGCSE (Year 10-11) ?!! I don't know half the words there.
    😂 I was joking, I have no idea what's going to come up on your exam... :P and I doubt that anyone does apart from the people that wrote it! I'm afraid you're just going to have to revise like the rest of us eh
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    hey could u please give me tips on the essay question
    thanks in advance
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    (Original post by girl :D)
    hey could u please give me tips on the essay question
    thanks in advance
    Erm, so I don't know if you've been told this, but the best thing to do is to write 4 paragraphs, and 3 of them need to be on different areas of the syllabus, the different areas include biochemistry, genetics, ecology and physiology. I actually wrote 5 paragraphs, just incase, but 4 good paragraphs on 3 different areas of biology will get you a lot of marks (obviously the bulk of the marks comes from how accurate your science is). The remaining 6 available marks are for spelling/punctuation etc, these are pretty standard marks to get, hopefully. The final 3 marks are for off-spec content, you need 2 bits of relevant off-spec facts to get 3 marks I think, they're usually the hardest to get.

    I actually got mugged on my essay, they marked it wrong apparently, but I had only lost like 4 UMS overall or something so I didn't get a remark. But yh the marking for the essay is pretty dodgy, the average mark is 13-16ish, I got 16, but apparently I should have got higher!

    As for useful websites, I didn't really use any, apart from wikipedia, which is pretty good to just get a general understanding of something
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    (Original post by AortaStudyMore)
    Erm, so I don't know if you've been told this, but the best thing to do is to write 4 paragraphs, and 3 of them need to be on different areas of the syllabus, the different areas include biochemistry, genetics, ecology and physiology. I actually wrote 5 paragraphs, just incase, but 4 good paragraphs on 3 different areas of biology will get you a lot of marks (obviously the bulk of the marks comes from how accurate your science is). The remaining 6 available marks are for spelling/punctuation etc, these are pretty standard marks to get, hopefully. The final 3 marks are for off-spec content, you need 2 bits of relevant off-spec facts to get 3 marks I think, they're usually the hardest to get.

    I actually got mugged on my essay, they marked it wrong apparently, but I had only lost like 4 UMS overall or something so I didn't get a remark. But yh the marking for the essay is pretty dodgy, the average mark is 13-16ish, I got 16, but apparently I should have got higher!

    As for useful websites, I didn't really use any, apart from wikipedia, which is pretty good to just get a general understanding of something
    Thnku soo much great help as always and lol 4 UMS!!!! ill be lucky to get that in total
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    (Original post by girl :D)
    Thnku soo much great help as always and lol 4 UMS!!!! ill be lucky to get that in total
    I reckon it's statistically easier to get full UMS than to get only 4 UMS haha, oh and btw, my previous comment should have said you only get 3 marks for punctuation/grammar etc, not 6 marks.

    Good luck, essay is pretty fun tbh, it's a good opportunity to boost that UMS
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    (Original post by AortaStudyMore)
    I reckon it's statistically easier to get full UMS than to get only 4 UMS haha, oh and btw, my previous comment should have said you only get 3 marks for punctuation/grammar etc, not 6 marks.

    Good luck, essay is pretty fun tbh, it's a good opportunity to boost that UMS
    Lol not for me..especially with bio anyway😂😂😂😂.
    Oh me 2, i find it really hard to stop writing once i start an essay i actually get to show the examiner all that i know on that topic...so yh, its wayyyy more fun the damn unit papers.
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    (Original post by AortaStudyMore)
    What's your logic behind that? :P I've never come across the concept before, but if you remember the main strong acids (HCl, H2SO4, H3PO4) then it will be a pretty safe bet that any others are weak. Don't get bogged down in this, unless you need to for your course? Even I didn't really ever come across this, and I did a lot of random research during my A-levels haha
    Dude that ain't a random research ... I gotta know this crap
    Btw our teacher told us that when a bronsted lowry acid loses a proton it becomes a conjugate base and when a bronsted lowry base accepts a proton it becomes conjugate acid.....
    So if an acid is strong, the conjugate base is weak and vice versa....
    GRRRRR!!!!! so whatcha think bout NH4+ now??
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    (Original post by Aimen.)
    Dude that ain't a random research ... I gotta know this crap
    Btw our teacher told us that when a bronsted lowry acid loses a proton it becomes a conjugate base and when a bronsted lowry base accepts a proton it becomes conjugate acid.....
    So if an acid is strong, the conjugate base is weak and vice versa....
    GRRRRR!!!!! so whatcha think bout NH4+ now??
    Okay so, you're kind of right, but what you're forgetting here is that strength is on a spectrum, anything that doesn't fully ionise in solution is weak, and something that fully ionises in solution is strong. However, something that is weak can still be comparitively strong compared to another weak acid (or base). So yes, you're almost right in saying that a strong acid has a weak conjugate base, but technically, what happens is the stronger the acid is, the weaker the conjugate base is. So a strong acid will make a weak conjugate base, but that conjugate base is on a spectrum from very weak, to not so weak. Likewise, NH3 (which is the conjugate base of NH4+) is actually quite a strong weak base. It's still technically weak, because it doesn't fully ionise, but it actually ionises quite a lot compared to other weak bases. So NH3's Kb is relatively high, but the very fact that it has a Kb means that it is a weak base. Now, Ka of the conjugate base = Kw/Kb, if you do some maths, this will tell you that the Ka of NH4+ is very low, so therefore it is a very weak acid.

    So in summary, the stronger the acid, the weaker the conjugate base, and the stronger the base, the weaker the conjugate acid. But weakness is on a spectrum, so you can have weak bases with weak conjugate acids
 
 
 
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