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    (Original post by smozsolution)
    I've literally just woken up from a 20 minute turned 2 hour nap so if this is jumbled then I'm sorry haha.

    A gene therapy is a therapeutic technique where the functioning allele of a particular gene is placed in the cells of an individual lacking in the functioning alleles of that particular gene.

    Somatic Cell Gene Therapy has two types:
    Augmentation (adding genes) is where a faulty allele for a gene may lead to the organism being unable to synthesise an important protein. Augmentation is where a functioning copy of the gene is inserted, and the protein can now be synthesised.
    Killing cells is where cancerous cells can be engineered to produce a particular protein (e.g cell surface antigens), causing an immune response. This may lead to a new way to treat cancer.
    It must be repeated regularly as it is a short term treatment as the specialised cells containing the gene will not often divide to pass on the allele.
    It is difficult to get the gene into the genome in a functioning state. Liposomes have been trialled to do this, as they are made from the same lipid bilayer as the cell membrane, and can therefore pass straight through. Genetically modified viruses have also been tried but the host becomes immune to them so the cell will not accept the vector on following treatments.

    Germline Cell Gene Therapy
    The germline cells are the sex cells, sperm and egg, but this therapy can also work for zygotes too.
    The functioning allele is introduced into germline cells so all cells derived from the germline cells will have a copy of the functioning allele. This means the patient could potentially pass on this allele to their offspring.
    This, however, is considered unethical in humans because there could be unintentional changes that may damage the embryo, it raises ethical issues of whether we should genetically engineer embryos, we could interfere with human evolution in ways we do not know.

    If there's anything incorrect, feel free to correct me anyone. I hope this helps
    Thankyou very much this helped
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    (Original post by CountessDracula)
    Hey guys. I was just wondering. How far is everyone with revision for F214 and F215?
    notes on everything but the end of the kidney and liver and the end of animal behaviour. wbu?
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    (Original post by CountessDracula)
    Hey guys. I was just wondering. How far is everyone with revision for F214 and F215?
    We haven't even finished everything yet, but I'm pretty up to date with all my notes. Need to finish stuff on ecosystems and plant hormones, but I'm just trying to get only the stuff we need, seems we've been taught a lot extra
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    How do auxins cause cell elongation? Could someone please give a detailed response as the textbook is pretty vague with the details

    If anyone's started past paper questions - what kinds of questions have you come across so far about auxins/ plant hormones in general?
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    We got ecosystems the whole module and most of biotechnology module because we only done 3 topics!!! Stressed out hardcore revision I'm doing F212 F214 F215
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    (Original post by 96akhan)
    How do auxins cause cell elongation? Could someone please give a detailed response as the textbook is pretty vague with the detailsIf anyone's started past paper questions - what kinds of questions have you come across so far about auxins/ plant hormones in general?
    The presence of auxin in plant cells promotes hydrogen ions to be actively transported through the enzyme ATPase and into the cell wall. This decreases the pH, providing the optimum conditions for wall loosening enzymes to work, known as expansins. These enzymes break the bonds within the cellulose cell wall, making the cell less rigid and causing water to move in by osmosis. This causes the elongation.

    Hope this helps
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    F215 June 2013 Questtion 6.a.ii

    'Heterozygote shows a distinct phenotype'

    Is only for species T according to the mark-scheme. I originally thought a distinct phenotype = one of the distinct categories for a phenotype that varies discontinuously. However this would suggest a heterozygote would be for both species S and T.

    Take species R for example. This is discontinuous, with 2 discrete categories.
    --> controlled by a single gene.
    --> involves just two alleles
    --> involves a dominant and a recessive allele

    Now species T. This is discontinuous also, but with 3 discrete categories.
    --> controlled by a single gene.
    --> involves just two alleles
    --> shows co-dominance or incomplete dominance

    For the point 'heterozygote shows a distinct phenotype' i would have thought it would go in both, because a distinct phenotype = a discrete category. This is wrong and it only goes into T.

    Imagine species R

    We have one gene - two alleles - one dominant, one recessive.
    3 possible genotypes:
    RR = high resistance
    Rr = high resistance
    rr = low resistance

    So even though 'high resistance' and 'low resistance' ARE two discrete categories, there are two possible genotypes which code for high resistance and thus a heterozygote does not show a distinct phenotype.

    So a distinct phenotype is coded for by only one genotype.

    Take species T

    HH=High resistance
    LL = low resistance
    HL = intermediate resistance

    Hence for T, a heterozygous genotype codes for 'intermediate' phenotype and is the only possible genotype to do so.

    I believe this is the correct way of thinking this question through?

    Rather a-lot of work for a simple fill in the table question i must say.
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    (Original post by smozsolution)
    The presence of auxin in plant cells promotes hydrogen ions to be actively transported through the enzyme ATPase and into the cell wall. This decreases the pH, providing the optimum conditions for wall loosening enzymes to work, known as expansins. These enzymes break the bonds within the cellulose cell wall, making the cell less rigid and causing water to move in by osmosis. This causes the elongation.

    Hope this helps
    Thank you!!
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    Also, when it says 'involves just two alleles' and 'may involve multiple alleles'.

    Does this mean...

    Involves just two alleles = in existence there are two alleles of the gene, of which two are found at the particular gene locus.

    May involve multiple alleles = in existence there are more than two alleles of the gene, of which two are found at the particular gene locus.

    Because saying 'involve multiple alleles' is extremely misleading to candidates, when there can only ever be two alleles at a particular gene locus. One maternal, one paternal.

    The emphasis should be 'invloves two possible alleles' and 'may involve multiple possible alleles'

    Because at any particular gene locus it just 'involve just two alleles' and so I'm sure some candidates that sat this paper placed this in every box, because indeed two alleles are involved at each gene locus.

    Am I correct in saying all this?
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    Is there any revision packs or really good techniques to get full makrs?
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    (Original post by Solid221)
    Is there any revision packs or really good techniques to get full makrs?
    >> revision packs may be good, but the person using it won't necessarily get full marks without exam tech.
    Just keep working with whatever revision technique works best for you. Do practice questions, see where you go wrong, find a good way to memorise the things you forget, or go over those concepts you're a little iffy with. Don't avoid the things you're bad at, tackle them first. Papers are a good way to find your problem areas
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    (Original post by AnnekaChan173)
    It's actually surprisingly ok! You could honestly learn it on your own tbh
    This gave me some hope :ahee: going to start on it then!

    Posted from TSR Mobile
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    Can someone please explain the experimental evidence for gibberellins causing stem elongation - it's the stuff about the Le and le alleles and grafting a pea plant but I'm completely baffled :confused:
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    do we need to know sickle cell anaemia in detail? and what do we need to know about homeobox genes? so much to learn so little time
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    (Original post by tewas)
    do we need to know sickle cell anaemia in detail? and what do we need to know about homeobox genes? so much to learn so little time
    homeotic codes for body plans and are similar through multiple organisms (fungi, drosophila)
    Homeotic genes have homebox sequences, which code for the transcription factor (homeodomain) that that binds to the operator.
    It's the homeodomain that binds to the operator of the gene that acts as a repressor/activator.

    If anyone has anymore to say or corrections to that, please add some in
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    (Original post by ChoccyPhilly)
    homeotic codes for body plans and are similar through multiple organisms (fungi, drosophila)
    Homeotic genes have homebox sequences, which code for the transcription factor (homeodomain) that that binds to the operator.
    It's the homeodomain that binds to the operator of the gene that acts as a repressor/activator.

    If anyone has anymore to say or corrections to that, please add some in
    Nah that's pretty much it, just homeodomain binds at the start of developmental genes so acting as an activator or repressor depending on the body plan's so altering protein production for the development of the body plan.
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    Okay so I can't remember anything about chromosomes, where are they located in the cell lol?
    diploid and haploid numbers, what does 2n and n mean?
    Someone briefly explain all of that, would be fab
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    (Original post by frozo123)
    Okay so I can't remember anything about chromosomes, where are they located in the cell lol?
    diploid and haploid numbers, what does 2n and n mean?
    Someone briefly explain all of that, would be fab
    Chromosomes are found in the nucleus of the cell.
    Haploid - half the number of chromosomes found in a normal cell, hence n. For example, in sperm and egg cells there are 23 chromosomes as they are half of the 46 chromosomes found in a normal cell.
    Diploid - having a normal number of chromosomes in a cell, i.e a full set. This is where the 2n comes from as for normal human cells, it's 46 (which as you know, is double 23 so n must be 23 in the case of humans).

    Hope this helps
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    Hi guys I want to know some ways to remember all the biology content, because I keep forgetting it.
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    (Original post by smozsolution)
    Chromosomes are found in the nucleus of the cell.
    Haploid - half the number of chromosomes found in a normal cell, hence n. For example, in sperm and egg cells there are 23 chromosomes as they are half of the 46 chromosomes found in a normal cell.
    Diploid - having a normal number of chromosomes in a cell, i.e a full set. This is where the 2n comes from as for normal human cells, it's 46 (which as you know, is double 23 so n must be 23 in the case of humans).

    Hope this helps
    are chromosomes made up of DNA then?
    so the 46 chromosomes, one chromosome from the father, one from the mother? 23 pairs?

    but in haploid cells, the number of chromosomes have been halved so there's 23 chromosomes in each cell? how do they pair up?
    and then how do they half again? ( not the process) but the concept of n
    lol so confused
 
 
 
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