Chapter 13

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Chapter 13
2015-12-01 00:15:55
Test Three: Zuzga
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  1. What does T4 attach to?
    OmpC- porin
  2. What is the time course of T4 phage infection
    bacteriophage attaches and injects DNA into cell

    transcription of phage DNA begins (1 minute)

    bacterial DNA broken down and nucleotides used (3 minutes)

    translation of phage mRNA and formation of new phage particles as capsids are produced (12 minutes)

    Cell bursts and new phages are released (22 minutes)
  3. Explain the transcriptional cascade
    The first set of T4 genes are transcribed by the E. coli RNA polymerase, using a standard sigma 70 subunit to bind to RNA polymerase

    The modification of the sigma 70 subunit leads to transcription of a second set of T4 genes

    Replaced with sigma 55 leads to transcription of a third set of T4 genes
  4. Lysogenic to lytic switch
    prophase excised and circularized

    Rolling circle replication, which gets cleaved into concatamers by endonuclease

    pacaging into capsid and recircularization
  5. Variation of viral production and release in eukaryotes
    a) release of stored viruses: crystalline inclusion containing many virus particles that eventually gets released

    b) continual extrusion of viruses: viral DNA being released in a membrane bound virus
  6. What does the retroviral genome consist of?
    gag: codes for the core structural proteins

    pol: codes for reverse transcriptase

    env: codes for viral proteins

    other genes embedded-- integrase is part of pol
  7. long terminal repeats
    contain viral promoters

    adjacent to packaging sequence

    involved in viral integration
  8. Production of a replication incompetent virus for gene therapy
    1) construct with "therapeutic gene" contains packaging sequence

    2) construct with gag, pol, env does not contain packaging sequence

    3) only construct with "therapeutic gene" is packaged into virus

    4) virus can integrate therapeutic gene but cannot produce infectious virus
  9. Explain the virus therapy with a certain disease.
    severe combined immunodeficiency: patients have trouble getting their BCs to differentiate

    bacterium carrying plasmid with cloned normal human ADA gene+ genetically disabled retrovirus--> cloned ADA gene is incorporated into virus--> retrovirus infects T cells, transfers ADA gene to cells, which are grown, leading to a genetically altered group of cells, which are able to produce ADA
  10. Downside to this therapy
    There was an overexpression of IL7 and IL 15, leading to the blockage of the pathway by LMO2 overexpression

    1) Integration occurred upstream of the LMO2 gene

    2) The strong viral promoter directed high levels of LMO2  expression since the therapeutic gene was placed before it

    3) Blocked "differentiation" of T-cells allowing them to continually proliferate

    4) development of leukemia
  11. Retrotransposon mechanism
    they are mobile elements

    Transcription of the retrotransposon into ssRNA--> reverse transcription into dsDNA--> reintegration
  12. prions
    infectious protein

    misfolded protein in low energy state

    induces misfolding in normal protein

    forms aggregates
  13. concept of the selfish gene
    genes are segments of DNA or RNA and act as replicators

    genes may replicate at the expense fo the individual

    the force of natural selection operates on genes rather than on individuals

    alleles are in comp with one another

    increasing the fitness of an individual or vehicle or host is but one means of replciation