Biology 4

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Biology 4
2013-01-22 21:10:57
Gene Expression Tony Russell Biology Genetics

Cards on Gene Expression, now superceded. Use this as a backup.
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  1. What is a Clone?
    • Two or more identical cells or organisms.
    • Identical Twins are natural clones.
  2. What do Restriction Endonucleases do?
    Restriction Endonucleases cut DNA at or near specific base sequences.
  3. A restriction endonuclease is taken from S. Pneumoniae.
    The enzyme is derived from strain a, and is the third of five endonucleases.
    What would be the name of this Restriction Endonuclease?

    • The first letter (S) comes from the genus (Streptococcus), the following two from the species (Pneumoniae).
    • The A comes from the particular strain it was derived from.
    • The III describes which particular Restriction Endonuclease (if there are multiple).
  4. Which organism might we use to derive the Restriction Endonuclease SmaAII from?
    A) Ebolavirus Zaire
    B) Streptococcus Rabidae
    C) Escherachia Coli
    D) Serratia Marcessens
    D) Serratia Marcessens
  5. Which bacterium does HindII come from?
    A) Haemophilus Influenzae
    B) Haemophilus Islitidae
    C) Haemophius Anarchedae
    A) Haemophilus Influenzae
  6. What is the specific sequence that HindII recognizes?
    • -GTPy||PuAC-
    • -CAPu||PyTG-
    •  *(The "||" indicates the cleavage point).
  7. Different Restriction Endonucleases will recognize different length sequences. Will a Restriction Endonuclease requiring a longer sequence cut more or less frequently than one requiring a short sequence?
    • A Restriction Endonuclease that recognizes a long sequence will cut less frequently than one requiring a short sequence.
    • e.g A Restriction Endonuclease recognizing six bases will cut the DNA once in approximately 46 bases, whereas one recognizing four will cut one in approximately 44.
  8. What is a Rare Cutter?
    A restriction enzyme that cuts only rarely because it's recognition site is uncommon.
  9. Give one example of a Rare Cutter.
    NotI (8 Base recognition sequence).
  10. The terms Heteroschizomers and Neoschizomers are used interchangeably. What do they mean?
    Neo-/Heteroschizomers refer to two Restriction Endonucleases that recognize exactly the same sequence but cleave it at different places.
  11. Two different Restriction Endonucleases that cut at the same place on the same site of DNA are known as?
  12. What is being shown in the picture?
    • Most noteably Sticky Ends as a result of asymmetric cleavage.
    • Also, the sequence is palindromic.
  13. What feature of Restriction Endonuclease recognition sites make it possible for the enzyme to cut asymmetrically?
    The recognition site is palindromic, so often the Restriction Endonuclease is recognizing the same bases, only in reverse.
  14. What is the role of Methylase?
    Methylase methylates native DNA to stop Restriction Endonucleases from cleaving it.
  15. What is the R-M System?
    R-M Stands for Restriction Methylation. This is the system by which native DNA is methylated to stop Restriction Endonucleases from cleaving it.
  16. Why might Restriction Endonucleases be useful if not for cutting up Native DNA?
    Restriction Endonucleases serve to cut up foreign DNA to stop infection from other organisms. Most notably Viruses.
  17. How come newly replicated DNA is not cleaved by Restriction Endonucleases?
    Due to the semiconservative nature of DNA, although the new strand my not be methylated, the precusor strand will be. Restriction endonucleases need to be able to interact with both strands to cleave, therefore one methylated strand will prevent the whole thing.
  18. Using one Restriction Endonuclease, a DNA Ligase and two related but different plasmids. How might you go about making a recombinant?
    • Combine the Restriction Endonuclease with the two plasmids, so they cleave them at the same sequence (assuming they share one).
    • The result will be two linear DNA molecules with complimentary sticky ends.
    • Allow the two plasmids to anneal together (sticky ends join up).
    • Use DNA ligase to complete the phospodiester backbone.
    • Finally, screen for recombinants (as this process is not 100% effective).