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    (Original post by Remarqable M)
    I'm back lol i will be self teaching module 4 as i don't see how we're going to finish everything within 5 weeks
    unit 2 content is a nightmare to read! you'll have to literally burn yourself(a.k.a cramming) to memorise everything.
    heeeeey, you've probably been busy but just asking if you've done anymore question packs for any mods? Mod 4 is good, well we've started it in class... the brain is like WOW!
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    (Original post by Remarqable M)
    No comment on module 1:lol: seriously this module is a martyrdom! :eek3: SO far my favourite modules in this unit are module 2(not everything though), 3 and 4. There is nothing in those modules that makes me want to sleep unlike in module 1( except protein sythesis/lac operon which i found incredibly fascinating). i feel really sorry for you, because you're miles behind to put it simply you're the 'last runner in this marathon' lol
    LOOL thats no helping now is it xD.
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    Could someone explain how the genome of an organism is sequenced to me please? (P166 - 167 OCR Heinemann book). What does it mean by 'Genome are first mapped to identify which part of the genome they have come from'.. does that mean the genome is sequenced in sections and not as a whole? Argh, confusing me so much ><
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    We've just finished the syllabus now...time to get memorising!
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    (Original post by Remarqable M)
    No comment on module 1:lol: seriously this module is a martyrdom! :eek3: SO far my favourite modules in this unit are module 2(not everything though), 3 and 4. There is nothing in those modules that makes me want to sleep unlike in module 1( except protein sythesis/lac operon which i found incredibly fascinating). i feel really sorry for you, because you're miles behind to put it simply you're the 'last runner in this marathon' lol
    LOL omg, that made my day! ahaha

    You don't even understand how badly biology is RUINING my life! :bawling:
    But yeah, I'm getting pretty bored of module 1. Haven't even started module 3, I'd say module 4 is the most interesting so far.
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    (Original post by smflesh)
    Could someone explain how the genome of an organism is sequenced to me please? (P166 - 167 OCR Heinemann book). What does it mean by 'Genome are first mapped to identify which part of the genome they have come from'.. does that mean the genome is sequenced in sections and not as a whole? Argh, confusing me so much ><
    Yeah sure I'm assuming you are mean sequencing a BAC section using overlapping fragmentation analysis...

    Because there is also the other method to sequence genomes..automated sequencing using the marked nucleotides...

    Ok , with sequencing, you can only carry the process out of sections of DNA that are around 750 base pairs long. So that means you cannot do the whole genome in one go, and it has to be sequenced in sections. But in order for it to be an accurate copy of the genome the process must be carried out several times, on overlapping fragments of the DNA, so that these can be analysed and used to put the whole genome back together.

    Firstly you have to map the genome-find out where it has come from on the chromosome, and usually already known information is used to do this...there are various ways.

    You then cut it up into around 100,000 base pairs, and placed into BACs. TheBACs are cultured and are known as clone libraries.

    You then take a specific BAC and extract the DNA and break it into smaller fragments by use of restriction enzymes.
    The fragments will be different sizes as different restriction enzymes are used, which cut it in different places.
    Electrophoresis is used to seperate out these lengths.
    This are then analysed by a computer program, to compare overlapping regions, to allow the whole genome to be assembled.
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    (Original post by ViolinGirl)
    Firstly you have to map the genome-find out where it has come from on the chromosome, and usually already known information is used to do this...there are various ways.
    Thank you so much! But re. the quoted part.. we have to map the whole genome of the organism to find what on the chromosome ? Are you referring to the approx. 750-length base DNA?
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    (Original post by ViolinGirl)
    ooh. Share the knowledge. I don't think I understand recessive/dominant epistatis well, so explain that if you are able
    oh god! no no!:lol: my heads hurts now, trying to remember epistasis:p: ok i wil try and see what i can remember so far, epistasis is the interaction between linked genes. One gene can mask or supress the expression of an another gene(for a different trait). They either work together or work against each other(antagonistally). Dominance is different to epistasis in that it is the interaction between alleles at the same gene locus. :eek3: epistasis is like a vampire sucking my blood:eek: i'm afraid this is all i can tell you about epistasis
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    (Original post by ViolinGirl)
    Yeah sure I'm assuming you are mean sequencing a BAC section using overlapping fragmentation analysis...

    Because there is also the other method to sequence genomes..automated sequencing using the marked nucleotides...

    Ok , with sequencing, you can only carry the process out of sections of DNA that are around 750 base pairs long. So that means you cannot do the whole genome in one go, and it has to be sequenced in sections. But in order for it to be an accurate copy of the genome the process must be carried out several times, on overlapping fragments of the DNA, so that these can be analysed and used to put the whole genome back together.

    Firstly you have to map the genome-find out where it has come from on the chromosome, and usually already known information is used to do this...there are various ways.

    You then cut it up into around 100,000 base pairs, and placed into BACs. TheBACs are cultured and are known as clone libraries.

    You then take a specific BAC and extract the DNA and break it into smaller fragments by use of restriction enzymes.
    The fragments will be different sizes as different restriction enzymes are used, which cut it in different places.
    Electrophoresis is used to seperate out these lengths.
    This are then analysed by a computer program, to compare overlapping regions, to allow the whole genome to be assembled.
    wow amazing how you could remember all that:sigh:
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    (Original post by smflesh)
    Thank you so much! But re. the quoted part.. we have to map the whole genome of the organism to find what on the chromosome ? Are you referring to the approx. 750-length base DNA?
    Yes, the 750 base pair section. To find out which part of the genome the sample you are using has come from.
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    (Original post by Remarqable M)
    oh god! no no!:lol: my heads hurts now, trying to remember epistasis:p: ok i wil try and see what i can remember so far, epistasis is the interaction between linked genes. One gene can mask or supress the expression of an another gene(for a different trait). They either work together or work against each other(antagonistally). Dominance is different to epistasis in that it is the interaction between alleles at the same gene locus. :eek3: epistasis is like a vampire sucking my blood:eek: i'm afraid this is all i can tell you about epistasis
    Aww. I expected more Remarqable M. :p:

    I know that epistatis is the interaction between different gene loci, where one gene locus can mask or supress the expression of another gene locus. And that epistasis can be both anatagonistic or complementary.
    Anatagonistic is where they work against each other, so the presence of one gene on the first locus may prevent the epression of a gene on the second locus.
    Complemetary action I think is where the expression of one gene at first locus, allows for the expression of another gene at a second locus. So say...if it were in control of the flower colour, the gene expressed at the first locus would code for a white flower, and if a gene was expressed at a second locus for pink colour then it could be expressed due to the presence of the other one. But if white allele was absent then it couldn't.

    But then that just makes it sound like antagonistic action. So I am confused here...

    I wanted to know about recessive epistasis and dominant epistasis when I asked that question. I think I get them now.

    That recessive epistasis is when the expression of a recessive allele ( homozygous) prevents the expression of another gene at the second locus.

    And dominant epistasis is where the prescence of a single dominant allele or two dominate alleles preventing expression of another gene at second locus...

    maybe...hmmm...
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    (Original post by ViolinGirl)
    Aww. I expected more Remarqable M. :p:

    I know that epistatis is the interaction between different gene loci, where one gene locus can mask or supress the expression of another gene locus. And that epistasis can be both anatagonistic or complementary.
    Anatagonistic is where they work against each other, so the presence of one gene on the first locus may prevent the epression of a gene on the second locus.
    Complemetary action I think is where the expression of one gene at first locus, allows for the expression of another gene at a second locus. So say...if it were in control of the flower colour, the gene expressed at the first locus would code for a white flower, and if a gene was expressed at a second locus for pink colour then it could be expressed due to the presence of the other one. But if white allele was absent then it couldn't.

    But then that just makes it sound like antagonistic action. So I am confused here...


    I wanted to know about recessive epistasis and dominant epistasis when I asked that question. I think I get them now.

    That recessive epistasis is when the expression of a recessive allele ( homozygous) prevents the expression of another gene at the second locus.

    And dominant epistasis is where the prescence of a single dominant allele or two dominate alleles preventing expression of another gene at second locus...

    maybe...hmmm...
    No, it does not make it antagonistic action, but i agree it sounds antagonistic. Remember it is antagonistic if the gene is present not absent.
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    (Original post by ViolinGirl)
    Yes, the 750 base pair section. To find out which part of the genome the sample you are using has come from.
    Thank you, +rep!
    Oh and have you done DNA probes yet? If I'm correct.. the probe is a single stranded DNA complementary to the gene / base sequence you're searching for in a sample. The probe is labelled as it's radioactive. If what you're looking for is in the sample the probe bonds to it.. but how do we know the probe has found the gene / sequence we want? Does the colour emitted radioactively / flourescent marker change when it binds to what we're looking for.. or does it only emit the colour when it's binded to what we're looking for? Hopefully that made sense.
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    (Original post by smflesh)
    Thank you, +rep!
    Oh and have you done DNA probes yet? If I'm correct.. the probe is a single stranded DNA complementary to the gene / base sequence you're searching for in a sample. The probe is labelled as it's radioactive. If what you're looking for is in the sample the probe bonds to it.. but how do we know the probe has found the gene / sequence we want? Does the colour emitted radioactively / flourescent marker change when it binds to what we're looking for.. or does it only emit the colour when it's binded to what we're looking for? Hopefully that made sense.
    Thanks
    Hmm..Ive done DNA probes but not looked over it yet. Of what I can remember...

    Yes. A probe is a single stranded section of DNA that is about 50-80 nucleotide bases long. It is complementary to the gene you want to analyse/are looking to find. As the fragments of DNA in your sample are single stranded due to use of restriction enzymes, then the DNA probe will anneal (bind to by hydrogen bonds) to the gene you want to locate. Yes, it is labelled with a radioactively coloured marker, and this will show up when photographic film is placed over it.

    Remember that the samples are first seperated out by electrophoresis, and then they are tranferred onto a sheet by use of nylon/nitrocellulose fibre sheet. The position of the probe used in the sample will transfer on this. And as it has been radioactively marked, its positon will show up when exposed to photographic film.
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    (Original post by Remarqable M)
    No, it does not make it antagonistic action, but i agree it sounds antagonistic. Remember it is antagonistic if the gene is present not absent.
    AHHH! Thanks
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    (Original post by ViolinGirl)
    Thanks
    Hmm..Ive done DNA probes but not looked over it yet. Of what I can remember...

    Remember that the samples are first seperated out by electrophoresis, and then they are tranferred onto a sheet by use of nylon/nitrocellulose fibre sheet. The position of the probe used in the sample will transfer on this. And as it has been radioactively marked, its positon will show up when exposed to photographic film.
    So does the radioactive probe only show up when it is attached to the length of DNA we're looking for? Since it's radioactive.. won't the probes (bonded / unbonded) also transfer onto the nitrocellulose and show up when photographic film is placed over it?
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    Alright folks! Let me go through my snickers bar + glass of milk+ banana .Time to roll.... post any questions except for the last module lol which err i think is based on animal-plant responses.
    EDIT: forgot to mention this: Its the first time in maybe two years time that i am drinking milk
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    (Original post by smflesh)
    So does the radioactive probe only show up when it is attached to the length of DNA we're looking for? Since it's radioactive.. won't the probes (bonded / unbonded) also transfer onto the nitrocellulose and show up when photographic film is placed over it?
    A probes detection depends on whether its radioactive o r not in this case obviously if its a radioactive, it will be detected by its decay there are also ones which don't necessary need to decay but radiate.
    The later part of the question i believe is to deal with electrophoresis? ok from what i can recall... since dna is an acid (-ve in nature) it will be attracted to the +ve end of the circuit.You will get dna length(fragments) of various sizes each ending with the the "labelled nucleotide" ones which are doubly de-oxidized and marked with colour.
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    Oh dear we still have module 3 & 4 to go, we are so behind.
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    (Original post by uer23)
    Oh dear we still have module 3 & 4 to go, we are so behind.
 
 
 
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