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DNA Repair system

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  • DNA Repair system

    DNA Repair system


    Cells have several enzymes that responsible for repairing damaged DNA. and each one of these enzymes works on only on a specific type or types of damaged DNA.

    Also these enzymes go under genetic control and they may undergo mutations

    DNA damage happens all the time, it occurs spontaneously and in all cells


    For example on these enzymes :


    1-DNA POLYMERASE have 3 activities{DNA polymerase , 3’ 5’ exonuclease and Removal of RNA primers by 5’→3’ exonuclease activity

    the function of 3’ 5’ exonuclease works if the bases does not match so the 3’ 5’ exonuclease function will remove it and the polymerase function remake the strand






    The function of 5’ 3’ exonuclease works to remove the RNA primers





    2- removal of T=T dimers by DNA photolyase

    T=T Dimers are A common Photoproduct of UV treatment of DNA in vivo and in vitro is an intra-strand dimer formed between adjacent thymines









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    There are two major types of mutation :-

    1- single strand break
    which is easily repaired by repair enzymes using the other strand as the templat





    2- Double-Stranded Break



    this kinds of Breaks cannot be repaired and lead to mutation during mitosis and also Often lethal because can't be resealed by ligase so degraded by nucleases


    The efficient repair of DSBs is crucial in maintaining genomic integrity, cellular viability, and the prevention of tumorigenesis.





    That is enough for today. I will talk about the mechanisms of DNA repair in soon as possible


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    التعديل الأخير تم بواسطة الواقع والحياد; الساعة 30-12-2007, 05:52 PM.
    http://www.gulfup.com/up/bmpfiles/NgB26887.bmp

  • #2
    إلى الأخت الواقع والحياد

    My sister that will be better then

    And I will be thankful for that
    http://www.gulfup.com/up/bmpfiles/NgB26887.bmp

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    • #3
      thanks Max112 for this subject and we are waiting the mechanisms of DNA repair

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