Bio Chapter 12

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Bio Chapter 12
2014-04-22 00:49:52

Bio Chapter 12 Notes
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  1. From Genes to Proteins
    Genes are coded DNA instructions that control the production of proteins. DNA never leaves the nucleus, therefore the code must be copied into RNA, or ribonucleic acid.
  2. Messanger RNA
    Serve as messenger from DNA to the rest of the cell.
  3. Ribosomal RNA
    Type of RNA that makes up parts of ribosomes.
  4. Transfer RNA
    Transfers each amino acid to the ribosome as it is specified by the mRNA
  5. siRNA
    Known as the silencing RNA. It helps by influencing which RNAs are translated.
  6. Transcription
    • DNA-> RNA
    • Transcription requires an enzyme known as RNA polymerase
    • During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucletoides are assembled into a strand of RNA.
    • 5 Prime to 3 Prime
    • Is for mRna, tRna and rRna
  7. Step One of Transcription
    Rna plymerase binds to the promoter site. RNA polymerase hooks together RNA nucleotides as they base pair along the DNA template.
  8. Tata Box
    Promoter DNA sequence 5'TATAAA_3'
  9. Step 2 of Transcription
    RNA plymerase moves along DNA template. It unwinds 10-20 DNA bases at a time. RNA polymerase adds nucleotides in the 5->3 direction. As RNA polymerase moves along, the DNA double helix reforms. The new section of RNA 'peels away' as the double helix reforms.
  10. Step 3 of Transcription
    • Transcription stops when RNA polymerase reaches a section of DNA called the terminator. Terminatior sequence= AAuAA
    • Next, the RNA strand is released and RNa polymerase dissociates from the DNA. The RNA strand will go through more processing.
  11. Translation
    Forming a polypeptide. Uses mRNA as a template for a.a sequence
  12. Three TRNA Binding sites
    • 1. A site= holds tRNA that is carrying the next amino acid to be added
    • 2. P site= holds tRNA that is carrying the growing polypeptede chain.
    • 3. E site= where discharged tRNAs leave the ribosome
  13. Translation
    • mRNA-> Ribosome
    • Uses tRNA to interpreter of mRNA
  14. Large and Small subunit of ribosomes
    each has three binding sites for tRNA on its surface. Each has one binding site for mRNA. Facilitates codon and anticodon bonding.
  15. Initiation Step 1
    Brings together mRNA, tRNA and ribosomal subunits
  16. Initiation Step 2
    • Small ribosomal subunits binds tomRNA and initiator tRNA
    • -Start codon= Aug
    • -Start anticodon=Uac
    • -Small ribosomal subunit attaches to 5prime end of mRNA
    • -downstream from the 5 prime end is start codon AUG (mRNA)
    • -After the union of mRNA, tRNA and small subunit, the large ribosomal subnit attaches.
  17. What is needed for initiation of RNA?
    tRNA mRNA small and Large subunit
  18. Translation of RNA
    Amino acids are added one by one to the first amino acid. Step one Codon recognition, mRNA codon in the A site forms hydrogen bonds with the tRNA anitcodon. Step 2- Peptide bond formation, The polypeptide extending from the P site moves A site to attach to the new a.a.
  19. RNA Translocation
    The tRNA w/ the polypeptide chain in the A site translocated to the P site. tRNA at the P site moves to the E site and leaves the ribosome.
  20. RNA Termination
    Happens at the stop codon (Uaa, Uag, and Uga) The polypeptides is freed from the ribosome and the reso of the translation assembly comes apart.
  21. Differences in gene expression between the two main types of cells
    • Prokaryotes= genes are a continuous streach of DNA
    • Eukaryotes= genes are fragmented. fragments are made of exons that are interrupted frequent by non-coding regions called introns.
  22. Introns
    not involved in coding for proteins
  23. Exons
    Code for protenis
  24. Each polypeptied contains a combination of any or all
    of the 20 different amino acids.
  25. The properties of proteins are determined by
    the order in which different amino acids are joined together.