Block One Lecture 10

  1. mRNA has __ and __

    rRNA has __. And, the ribosome itself is __.

    tRNA has __.
    poly A tail and G-cap

    • 4 basic sizes
    • slightly different from eukaryotes

    the same genetic code
  2. mRNA
    - moves where?
    -when does protein synthesis begin? 
    - complementary to __.
    moves right next to cytoplasm

    protein synthesis begins directly after 10-15 codons have been transcribed (almost simultaneous transcription and translation)

    complementary to the 3' end/ control sequences important because it makes sure it binds correctly
  3. Monocistronic definition

    Why are euk monocistronic?
    one gene, one product

    we have plenty of genes to waste
  4. Polycistronic

    one gene--several messages/ products (most is 7 so far)

    not a lot of space; so, tehy can't afford to waste anything; Bacteria have to utilize and replicate DNA
  5. Are the genes specific for each other in polycistronic DNA?
    one gene might have structural components, proteins for enzymes, etc. --> no net commonality
  6. Explain rRNA
    • 50S- large subunit
    • 30S- small subunit

    16S- main funciton is to make sure the subunits are lined up together

    5S: make sure the functional ribosome stays together
  7. Are the measured Svedburg units additive?
  8. tRNA

    - Why aren't there a lot of double-stranded RNA?
    double stranded RNA is a characteristic of viruses. So, it is a red flag to the immune system. In nature, the only naturally occurring RNA 12+ are viruses.
  9. tRNA has __.
    What are the four arms?
    four arms

    acceptor arms, TΨC arm, D arm and loop, Anticodon arm and loop
  10. If DS RNA is a red flag, why isn't tRNA a problem?
    the runs of DS-RNA are not enough to alert the body that it's a virus
  11. In bacteria, what do the D and T arms of tRNA act as? 

    The acceptor stems always end in what __.
    They are purely spacers. 

    Accepot stems always end in 3'-ACC
  12. Translation: __

    What's the same?

    Why are redundancies more important in bacteria?
    RNA--> protein

    same genetic code, redundancies, and limitations

    Because of their mutation frequency
  13. Bacterial ribosomes are __. How many sites are there?
    • nine bases wide
    • two: P and A site
  14. Explain wobble.
    When an anticodon of tRNA comes in to bind with the complementary mRNA codon, the middle base first base pairs with the codon. After, the tRNA will wobble one way and then another way to make sure the base pairs are proper. If it's wrong, the tRNA is completely thrown out.
  15. Explain what happens to the amino acids during translation
    amino acid in the site gets transferred to the tRNA in the A site.
  16. In some bacteria, what is the deal with the tRNA?
    some tRNA don't have stop codons. They are truncated. Others are just missing.
  17. Polyribosome complex
    about 21 bases long, the rbosomes bnd to the RNA and start translating
  18. Constitutive genes?
    genes that are transcribed at constant rates (they must be on from the first second of life to the last second of life)
  19. Repressible genes versus inducible genes?
    repressible: commonly turned on, but turned off when not needed

    inducible: commonly off, but turned on when needed
  20. Explain the promoter.
    Promoter: tells RNA polymerase where to bind. In some genes, the operator comes after and acts as an off-and-on switch. 

    Binds a class of proteins called repressors. When bound, the operator is off. When unbound, the operator is on. 

    The promoter and operator is always on a gene before the gene that they express
  21. The promoter, operator, and genes are __
    the operon
Card Set
Block One Lecture 10
Test One