DNA_ RNA and Protein Synthesis

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					DNA, RNA and Protein
     Synthesis
       Chapter 11
          DNA Structure
• DNA is a chain of
  Nucleotides
  – 3 parts of a
    Nucleotide:
     • sugar (deoxyribose)
     • Phosphate
     • nitrogen base -
       4 possible bases:
         – Adenine
         – Guanine
         – Thymine
         – Cytosine
           DNA Structure (continued)
• The DOUBLE HELIX
   – Double Stranded–
   – 2 sugar/ phosphate backbones
   – rungs = nitrogen base pairs
• Base-pairing rules
   – A-T
   – C-G
• The number and sequence of the
  nitrogen bases determines the CODE
  of the genes in the DNA!
                 DNA Replication
• DNA making copies of itself is called replication
• DNA replication is controlled by enzymes.
  2 of the main enzymes are:
   – Helicase: untwists the DNA
   – DNA polymerase: adds new nucleotides and connects them
• Structure of RNA
                            RNA
   – nucleotide
       • sugar= ribose
       • phosphate
       • nitrogen base (instead of
         thymine, RNA has Uracil).
           – Uracil is complementary to
             Adenine (it replaces
             Thymine)
   – Single stranded
Function of RNA
•    accomplish protein synthesis
                                    RNA
•    Why?--DNA is trapped in
     the nucleus but protein
     synthesis happens at
     ribosomes located in
     cytoplasm SO…
   – Messenger RNA (mRNA)
        is used to take the
        message from DNA to
        the ribosome
   – Ribosomal RNA (rRNA)
        attaches to mRNA and
        helps assemble proteins
   – Transfer RNA (tRNA)
        transfers (brings) amino
        acids to mRNA so that
        they can be attached to
        make a protein
                  Protein Synthesis
11.2 From DNA to PROTEIN
• I. The Purpose of DNA: DNA is used to make RNA which is used to
   make proteins!!
• (DNA--> RNA--> Proteins)
    – A. One DNA molecule has many GENES on it!
    – B. Gene—segment of DNA molecule that codes a specific protein.
             Protein Synthesis Step 1:
                  Transcription
TRANSCRIPTION
  – A. Transcription is the
    synthesis of mRNA
    using the code of a
    gene (DNA) as a
    template (pattern).
    Protein Synthesis Step 2: Translation
•    Translation (Converting the “language” of
     mRNA to the language of proteins.)
•    Codon= triplet of nitrogen bases on mRNA
    – Each codon codes for one specific amino acid
      •   Note: amino acids are the building blocks of proteins
      •   This code is universal- it applies to all organisms!
                   Translation continued…
     – The order of codons
       determines the order of amino
       acids found in the protein.
     – mRNA from nucleus is ‘read’
       along its codons
           • this occurs at the ribosome
           • tRNA has anticodons that are
             complementary to specific
             codons
           • Each tRNA can only bind one
             amino acid
           • tRNA transfers or transports the
             amino acids to the ribosome
             where they are attached (in
             order) to make a polypeptide
             chain.
•   Translation Animation ..\..\bio powerpoints\Chapter 11
    BDOL IC\GB4F605M.AVI
•   Analogy of Transcription through translation (RNAi
    explained)
•   http://www.pbs.org/wgbh/nova/sciencenow/3210/02.h
    tml
          Check for Understanding
•   DNA is a chain of ________
•   nucleotides
•   The three parts of a nucleotide are
•   sugar, phosphate, nitrogen base
•   The four possible DNA nitrogen bases are
•   A, T, C, G
•   What are the base paring rules?
•   A-T, C-G
Check for Understanding

				
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posted:7/7/2012
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