The main points of this lecture are:

  • there are 3 major forms of RNA
  • mRNA which is the "message"
  • rRNA which is the machinery/enzyme
  • tRNA which brings in the amino acids and "translates"

    1. mRNA is messenger RNA 

    - it is the actual linear "message" that is TRANSLATED into protein
    - the base sequence specifies which proteins will be made during translation

    2. rRNA is ribosomal RNA

    -  the RNA that is the "machinery" that makes proteins
    - it is structural in that proteins and the rRNA are assembled together into a globular structure like an enzyme
    - it is composed of 2 subunits

    3. tRNA is transfer RNA

    - There are 32 different tRNAs and each one binds a SPECIFIC  one of the 20 amino acid
    - it holds the amino acid in a physical position so it can be added onto the developing protein polymer chain 
    - each tRNA is the product of a separate gene or section of DNA  containing 73-93 nucleotides
    each has a "loop and stem" structure
    -  the stems are hydrogen bonded to give structure
    the paired and H bonded stems can form sections of double helix 
    -  the unpaired regions form 3 loops
    -  each tRNA carries (at its 3' end) the amino acid specific to that tRNA
    - the middle loop has the 3 unpaired bases that form the anticodon base 
    - it is the anticodon that pairs with the complementary codon on the mRNA molecule and brings the correct amino acid into alignment to be added to the growing polypeptide chain.

    What are the 3 kinds of RNA?
    What is their function and how are they different from each other?
    Describe what the different RNAs look like.