Tuesday, November 30, 2010

Transcription and Translation

Bridget 11/30/10

  • A chart for reading genetic codes.... know how to read this for the test
  • find first letter in center of circle
  • find second letter in the 2nd row
  • find third letter in 3rd row
  • 61 codes for amino acids- 3 of them, UAA, UAG, and UGA tell the ribosomes to stop making the polypeptide
  • AUG= Methionine but also provides signal to start a polypeptide chain
  • Most codes are shared by all organisms
DNA Replication
  • making exact copies of DNA in nucleus, occurs before cell division(mitosis/meiosis
    enzyme= DNA polymerase

  • molecule of DNA is copied into a complementary strand of mRNA
    enzyme=RNA polymerase

Steps of Transcription:

  1. Initiation- RNA polymerase attaches to the DNA promoter nucleotide sequence on DNA, RNA is made
  2. RNA elongation- RNA grows longer, peels away from DNA, DNA strands come back together
  3. Termination-RNA polymerase reaches the end of the gene (the terminator), polymerase molecule detaches from RNA molecule and the gene
Processing RNA:
  • Prokaryotes- the mRNA is already ready
  • Eukaryotes- need to proccess, add extra nucleotides
  • cap and tail-protect RNA from enzymes, help ribosomes recognize it as mRNA
  • introns- bad, noncoding regions
  • exons- good, cooding regions
  • RNA splicing- introns removed before RNA leaves nucleus
  • Now mRNA is ready!!!!
  • mRNA (Messenger RNA) translated into tRNA (Transfer RNA)
  • mRNA goes to ribosome
  • 2 subunits made of proteins and rRNA (ribosomal RNA)
  • small subunit- binding site for mRNA
  • large subunit- binding site for tRNA
  • tRNA-twists and folds, end of folded molecule=anticodon
  • anticodon recognizes codon on mRNA, then the other end of the tRNA is where an amino acid can attach
  • Bonds between (AA)s ((amino acids)) are peptide bonds
  • The polypeptide that is growing and forming is the protein!!

Steps of Translation:
  1. Initiation- mRNA binds to small ribosomal subunit, tRNA attached to amino acid binds to start codon, AUG on mRNA; large ribosomal subunit binds to small one, which creates a working ribosome
  2. Elongation- amino acids are added to the first amino acid, creating a polypeptide chain
  3. Termination- one of the stop codons tells the translation to stop. Polypeptide is freed ( many A.A), and ribosome splits into its subunits
RNA has:
  • Ribose sugar
  • 1 strand
  • U instead of T
  • smaller than DNA, can go inside/outside nucleus
  • 3 types: mRNA, tRNA, rRNA
Next scribe: Katie!! :)
  • UP 99-110 due 12/2
  • Pre-lab 37- cut out????
  • DNA/ Chicago Tribune Project Due next Tues.


  1. It helped me understand the the process of protein synthesis a lot better with the pictures of the notes that you put up. Nice job!! :]

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  3. I liked how you used pictures of the sketches we made in class. That helped with the understanding.

  4. I liked how you used the notes from class as put them into the post. I believe that this will help me when i am studying for finals

  5. I think you did a really good job on this post. You really fully explained the terms and took very detailed notes that help explain them to your peers. The pictures also help but I think you described the main point in your notes.

  6. DNA polymerase catalyzes DNA replication...
    TRANSCRIPTION: In INITIATION, RNA polymerase(the "password" to RNA) connects to DNA promoter sequence to create RNA.
    In ELONGATION, RNA grows and separates from DNA.
    In TERMINATION, the RNA reaches terminator(end) and polymerase detaches from RNA.

    cap & tail... protect RNA from enzymes, makes mRNA recognizable.

    Introns are useless.Must be removed, and then RNA can leave nucleus to prosper.

    TRANSLATION: m -> t
    Small subunit=mRNA, large subunit=tRNA
    Anticodons and codons find each other...

    Polypeptide bonds ultimately create protein.

    Good review, thanks Bridget