Ch 5 ID Terms

  1. transposition
    In this process, a specific enzyme (transposase) acts on a specific DNa sequence at each end of the transposon, causing it to insert into a new target DNA site
  2. Conservative site-specific recombination
    Recombination mechanism that mediates the rearrangements of other types of mobile DNA elements

    • Pathway: breakage and joining occur at two special sites, one on each participating DNA molecule; DNA integration, excision, or inversion can occur
    • Carried out by specialized enzymes that break and rejoin two DNA double helices at specific sequences on each DNA molecule
  3. mobile genetic elements
    Specialized segments of DNA that move and have, over the years, been altered so they are molecular fossils; cells cannot get rid of them, but do provide benefits to the cell if carrying a beneficial trait
  4. transposons (transposable elements)
    Mobile elements that move by way of transposition; can be inserted into many different locations in the genome; can be DNA-only, retroviral like retrotransposons, and nonretroviral retrotransposons
  5. DNA-only transposons
    Responsible for spread of antibiotic resistance

    can transpose only within cells that already carry them and can be moved from one cell to another through horizontal gene transfer

    can then insert into genome and pass on to progeny

    • can relocate from a donor site to a target site by cut and paste transposition or by replicative transposition
    • Move via DNA breaking and joining reactions
  6. Replicative transposition
    The transposon DNA is replicated during transposition: one copy remains at the original site while the other is inserted at a new chromosomal location.
  7. bacteriophage
    virus that infects bacterium

    ex: Mu uses DNA-based transposition and replicative transposition
  8. retrovirus
    • Virus that has a single-stranded RNA genome packed into a capsid and a reverse transcriptase enzyme
    • Viral RNA enters cell and is converted to a double-stradned DNA molecule by the action of reverse transcriptase, which polymerizes DNA on either an RNA or DNA template.
    • After making dsDNA, specific sequences near its two ends are held together by a virus-encoded transposase called integrase
  9. integrase
    creates activated 3'-OH viral DNA ends that can directly attack a target DNA molecule
  10. retroviral-like retrotransposons
    can move themselves in and out of chromosomes

    cannot leave resident cell but are passed to progeny

    Move via DNA breakage and joining but where RNA is a template
  11. Nonretroviral retrotransposons
    • the third major type of transposon-- few can move; a large fraction of vertebrate chromosomes are mostly mutated adn truncated versions of it; move via a distinct mechanism that requires a complex of an endonuclease and a reverse transcriptase
    • Many don't carry their own endonuclease or reverse transcriptase genes
    • Move via an RNA copy, which is central to the incorporation of the element into target DNA
  12. Bacteriophage lambda
    first mobile DNA element of any type to be understood; directs the synthesis of a virus-encoded recombinase enzyme called lambda integrase
  13. lambda integrase
    enzyme that mediates the covalent joining of the viral DNA to the bacterial chromosome, causing the virus to become part of this chromosome so that it is replicated automatically--as part of the host's DNA
Card Set
Ch 5 ID Terms
Test Two