exam 3 material

exam 3 material - 16:25:00 nucleotidestructure...

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30/10/2008 16:25:00 Structure of Nucleic Acids: nucleotide structure nitrogenous bases * purines (a=adenine, g=guanine) (double ring) * pyrimidines (t=thymine, c=cytosine) (single ring) all species the amount of A=T and G=C but each species has its own ratio of AT/GC model of how nucleotides combine to form a polymer Model for DNA structure: Mechanism for replication: PROCESS OF REPLICATION: (eucaryotes) Replication begins at the replication origin (up to 1,000 per DNA molecule) Helicase  enzymes SSB proteins  (single strand binding proteins) Primase  now builds a short RNA primer (~10 nucleotides) 5' to 3' DNA polymerase  enzymes now bind to the strand next to the primer and  catalyzes the addition of new nucleotides, one by one The DNA polymerase move only in one direction that is the new strand will  always be built from its 5' to its 3' end. DNA ligase
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Three questions of interest concerning this process 1. What happens if the wrong base is added to the growing strand? 2. Where does the energy for these reactions come from? 3. Why does DNA polymerase only build the new strand 5' to 3'? DNA Repair there are 50 or more repair enzymes which replace these damaged areas of  DNA with the appropriate nucleotides.
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30/10/2008 16:25:00 Central Dogma Transcription: write the information in DNA in the RNA Translation: Convert the information in RNA into the sequence of amino acids in  a protein. RNA RNA differs from DNA in: Three type of RNA: Messenger RNA (mRNA) : Ribosomal RNA (rRNA) : Transfer RNA (tRNA): TRANSCRIPTION: DNA to RNA RNA polymerase binds to DNA at a promoter site RNA polymerase builds the mRNA 5' to 3' direction only (complementary bases) When RNA polymerase reaches termination signal on DNA it leaves the DNA  template and so does the mRNA
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