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    (Original post by ibysaiyan)
    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.
    Sorry but you didn't really answer my question. What I essentially asked was how do you know if your DNA probe has ''found'' the DNA strand you're searching for?
    Am I correct in saying that you're DNA probe has found the DNA strand you're searching for if the probe appears next to the fragment of DNA on the nitrocellulose sheet? (Provided that the DNA probe + DNA fragments are marked using DNA marker?) Therefore for a negative result i.e. the strand of DNA you're looking for isn't in the sample, the DNA probes don't appear next to a DNA fragment (again provided radioactive markers used and Southern Blotting onto a nitrocellulose sheet and photographic film is applied over the n.c sheet)
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    (Original post by smflesh)
    Sorry but you didn't really answer my question. What I essentially asked was how do you know if your DNA probe has ''found'' the DNA strand you're searching for?
    Am I correct in saying that you're DNA probe has found the DNA strand you're searching for if the probe appears next to the fragment of DNA on the nitrocellulose sheet? (Provided that the DNA probe + DNA fragments are marked using DNA marker?) Therefore for a negative result i.e. the strand of DNA you're looking for isn't in the sample, the DNA probes don't appear next to a DNA fragment (again provided radioactive markers used and Southern Blotting onto a nitrocellulose sheet and photographic film is applied over the n.c sheet)
    Ok.
    Basically dna probes as you mentioned earlier can have radioactive nucleotides in them say for example potasium-32 which mits beta-radiation.Dna probes are made up of few xxx b.p.They hydrogen bond to any complementary base sequence i.e dna fragment " they dont need to be perfect complementary".
    Probes bind to sequences which are most complementary.
    Hope i made sense :/?
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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?
    Hmm. I'll try and answer this.

    Well, the probe will always bind to the fragment you are trying to look for as it is complementary to it. Look...you have the fragements present in the sample and the probe, during the separation in electrophoresis, the fragments are sepearting according to their length and the probe is annealing to the specific base sequence for which is is complementary to.
    The fragements can be stained previously to see how they move. But when they are transferred onto the nitrocellulose sheet, they are not visible. By placing photographic film over the sheet, the location of the probe will show up, and thus locating the required gene.

    I think...:o:
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    (Original post by ViolinGirl)
    Probe
    (Original post by ibysaiyan)
    Ok.
    Basically dna probes as you mentioned earlier can have radioactive nucleotides in them say for example potasium-32 which mits beta-radiation.Dna probes are made up of few xxx b.p.They hydrogen bond to any complementary base sequence i.e dna fragment " they dont need to be perfect complementary".
    Probes bind to sequences which are most complementary.
    Hope i made sense :/?
    Ibysaiyan: Yeah you made sense, but again didn't really answer my question sorry :/

    Okay, say for example both DNA fragments + DNA probes are radioactively labelled (so when transferred onto n.cellulose sheet, a photographic film placed over will show them up), a DNA probe will have found what the DNA fragment you're looking for if the probe appears next to a fragment?
    Conversely, if the probe hasn't found the DNA fragment, all the un-annealed probes will just appear randomly and not be next to any of the DNA fragments?

    Late-night revision ftw :p:
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    (Original post by smflesh)
    Ibysaiyan: Yeah you made sense, but again didn't really answer my question sorry :/

    Okay, say for example both DNA fragments + DNA probes are radioactively labelled (so when transferred onto n.cellulose sheet, a photographic film placed over will show them up), a DNA probe will have found what the DNA fragment you're looking for if the probe appears next to a fragment?
    Conversely, if the probe hasn't found the DNA fragment, all the un-annealed probes will just appear randomly and not be next to any of the DNA fragments?

    Late-night revision ftw :p:
    Ok as long as the "fragments" contains the gene you are after,yet it will.
    Answering the highlighted bit: Ok like I mentioned earlier dna probe tends to bind most combination of base sequence as long as its complementary (again doesnt need to be 100%) in the case you mentioned I would say if the probe doesnt find the particular fragment then it might bind to other complementary fragment.So they could either appear random (maybe) or binded to some other complementary fragment.


    lol :s
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    (Original post by ibysaiyan)
    Ok as long as the "fragments" contains the gene you are after,yet it will.
    Answering the highlighted bit: Ok like I mentioned earlier dna probe tends to bind most combination of base sequence as long as its complementary (again doesnt need to be 100%) in the case you mentioned I would say if the probe doesnt find the particular fragment then it might bind to other complementary fragment.So they could either appear random (maybe) or binded to some other complementary fragment.


    lol :s
    What you said about highlighted bit: Ah yeah, that's true. Ok I think I got the general hang of it, thank you ibysaiyin and violin girl
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    (Original post by smflesh)
    What you said about highlighted bit: Ah yeah, that's true. Ok I think I got the general hang of it, thank you ibysaiyin and violin girl
    Cool,I am glad it worked! lol sorry as i was sort of multi-tasking.. was doing maths past paper
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    How big is module 2? Is it *****? Its the last module I have left to self teach...
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    (Original post by v1oXx-)
    How big is module 2? Is it *****? Its the last module I have left to self teach...
    No, and it's actually less than module 1. There is only stuff on biotech, gene technologies, and gene therapy which is a piece of cake! :lol:
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    (Original post by ibysaiyan)
    Cool,I am glad it worked! lol sorry as i was sort of multi-tasking.. was doing maths past paper
    Don't worry, late-night revision ftw again:P
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    Module 4 is the best by far, it was hard but interesting.
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    I haven't really started hardcore revision yet but I'm finding Modules 3 and 4 ok overall, but some of Modules 1 and 2 really difficult. I find gene therapy and the stuff about PCR quite hard and I don't really understand epistasis in Module 1...
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    (Original post by smflesh)
    Don't worry, late-night revision ftw again:P
    Yep ftw!
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    (Original post by lil_miss_rapunzel)
    I haven't really started hardcore revision yet but I'm finding Modules 3 and 4 ok overall, but some of Modules 1 and 2 really difficult. I find gene therapy and the stuff about PCR quite hard and I don't really understand epistasis in Module 1...
    Ok from what i can rewind:
    Epistasis is the control of a phenotype by two or more genes i.e switching on/off a characteristic.
    Lets take mice coat color for an example
    Alleles for white color: bb
    Alleles AA/Aa:Agouti
    Alleles aa: Black.
    This is how it all starts off:
    If allele bb is present then the coat color of the mice will be white since tyrosine the precursor of melanin wont become melanin.
    If allele Bb/BB are present these convert tyrosine into melanin.This is done by the enzyme tyrosinase.
    And allele Aa/AA produces enzyme TYRP1 which dependsing on the allele combination varies melanin quantity.
    So say if one has AA: then the coat color would be Agouti.
    Note: A reminder black color in this case is recessive.
    Hope I made sense .
    Its lunch time i will post on cpr too.
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    (Original post by ibysaiyan)
    Its lunch time i will post on cpr too.
    You have your lunch now ? wow
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    (Original post by uer23)
    You have your lunch now ? wow
    LOl I know bit late. ;/ overslept as usual .
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    I'm bored. Anyone have a question? (except not on mod 4- not even started that! )
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    (Original post by lil_miss_rapunzel)
    I haven't really started hardcore revision yet but I'm finding Modules 3 and 4 ok overall, but some of Modules 1 and 2 really difficult. I find gene therapy and the stuff about PCR quite hard and I don't really understand epistasis in Module 1...
    PCR or Polymerase Chain reaction is basically the production or synthesis of more DNA(genetic material).Since in genome sequencing or in isolating a particular gene we would like to have various copies of the actual DNA(just to be on the safe side).How is this done? Here are the following steps:
    1) The whole structure of the DNA is basically de-stabilized such that the the H-H interaction between the nucleotides breakup.This is done at 95C.
    2)Now the single strands of DNA are exposed such that DNA polymerase could start off by attaching free dna nucleotides.(Note: DNA polymerase cant just start synthesizing new DNA it needs direction (guidance) this is done by the help of primers.So to cut it short: here annealing is done i.e adding primers,free DNA nucleotidesAt 65C.
    3)DNA polymerase comes into action here as its been adapted work at such a temp. at 72 C. :O viola! DNA.... and this step goes on and on.
    Note: These enzymes are extracted from micro-organism which survive at hostile temp.

    Hope Its clear to you now. Feel free to post any further questions.
    Regards.
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    (Original post by ViolinGirl)
    I'm bored. Anyone have a question? (except not on mod 4- not even started that! )
    Hello there =} hmm sure.. hmm I missed a lesson on population and sustainability.Could you explain me little on that please ? All I know is the prey-predator relationship.
    Thanks.
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    (Original post by ibysaiyan)
    Hello there =} hmm sure.. hmm I missed a lesson on population and sustainability.Could you explain me little on that please ? All I know is the prey-predator relationship.
    Thanks.
    Hello Yay...although I absolutely hate this topic I shall see what I can remember...

    Populations...

    Populations are dynamic, but most tend to remain fairly stable once they have reached the carrying capacity, perhaps only fluctuating slightly above and below the mean value of the population. The carrying capacity is the maximum population size that a habitat is able to maintain at a certain point in time.

    The carrying capacity of a habitat is determined by limiting factors, such as space, availability of food, water, oxygen, nesting sites etc.

    Population sizes can also rise or fall quite suddenly due to changes in the environment, or factors that are included within their ecological niche.
    Examples of the fluctuations in population sizes can be show by the predator/prey relationship.

    And since you know that...no need to explain.

    Hmm..

    The growth of populations can be modelled by a growth curve, which is in fact quite similar to that of microorganisms within a culture. There is a lag phase, in which the individuals of that population are still adjusting to the conditions present in the environment, so the rate of reproduction is low, and growth is slow. Then there is the exponential phase, in which the reproductive rate is greater than the death rate, as there is a wide availabilty of resouces which the organisms can make use of. This rate of increase in population size finally evens out in the stationary phase, as the habitat reaches its carrying capacity. The rates of reproduction and mortality are equal.
 
 
 
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