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Thread: working down a DNA thread what is to be found?

  1. #1 working down a DNA thread what is to be found? 
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    I just read that only 2% of human DNA codes for proteins although 80% of DNA is expressed (which I take to mean transcribes).


    This leaves me wondering what one would find, as one works one's way down a DNA thread?

    If a gene is a portion of DNA which codes for a mRNA, what does the rest do, if anything?

    Could someone give an explanation of what is going on in a DNA thread apart from coding for RNA

    My previous idea was that DNA was triplet sequences of base pairs, that code for particular amino acids (via MRSA) polypeptides and proteins; with stop codons seperating processes.

    A gene, to me, was a length of DNA containing Exons and introns, exons being (potentially) translatable into protiens and introns only reaching the trascription stage.

    It seems this is way too simplistic?


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    Forum Professor Zwirko's Avatar
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    2 am here, so just a quickie without too much thought on my behalf (apologies in advance if I only confuse).

    The term "gene" is a little bit like the term "life" - they are both essential aspects of biology, yet really hard to pin down in a neat catch-all phrase.

    Genes don't have to code for mRNA's. Many code for RNA's that do not act as messengers; for example, tRNA (transfer), rRNA (ribosomal) and an ever-growing collection of small RNA molecules that are involved in regulatory roles - so there are functional and informational RNA's. A gene itself consists of more than just a protein-coding sequence: there are all sorts of control regions, protein-binding sites and signalling stuff as well (gene structure would be something you could look over quickly).

    Much of the genome consists of a mess of repetitive genetic elements, that probably constitute upwards of 55% of the total sequence in humans; this includes things such as the transposons, retrotransposons and retroposons etc (the so-called "selfish genetic elements"). Interestingly, these elements are increasingly being seen as important agents in genome evolution. Also in the genome are things such as broken genes, inactive and active retroviruses, and fragments of DNA viruses. Many parts of the genome have sequences that have structural roles, such as telomeres and centromeres.


    The idea that most of the genome is transcribed into RNA is probably an error. RNA polymerases (the enzymes that makes RNA) have a habit of transcribing any old bit of DNA that they can get their hands on. Some overly sensitive assays coupled with some overly keen researchers led to the idea that most of the genome is transcribed. It's more than likely that this is just accidental transcription rather than a controlled expression of unknown genes with important function.


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  4. #3  
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    thank you for another excellent reply Zwirko,
    I will research your answer thoroughly you can be sure of this

    Could you do me a small favour and look over this post for me, its been up a while with no answer.

    http://www.thescienceforum.com/Mitos...ase-28800t.php


    I am sure you can correct any errors I might have made.

    thanks

    Zero
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