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Viral and bacterial genetics

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Which is expected in an enveloped virion?

  1. A nucleus, mitochondria and 80S ribosomes
  2. A genome and protein capsid with no lipid envelope
  3. A genome, capsid and lipid envelope with viral surface proteins
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A genome, capsid and lipid envelope with viral surface proteins

These are distinct structural components.

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Which structure is a prophage?

  1. Phage DNA integrated into the bacterial chromosome
  2. A bacterial plasmid containing only host genes
  3. A complete phage particle attached to the outside of a bacterium
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Phage DNA integrated into the bacterial chromosome

It can be inherited during bacterial division.

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Which statements are true of the lysogenic cycle of lambda phage? 1: Phage DNA integrates into the host chromosome. 2: The host cell bursts at once. 3: The prophage is copied when the host divides. 4: The prophage can later enter the lytic cycle.

  1. 1, 2 and 3 only
  2. 1, 3 and 4 only
  3. 2 and 4 only
  4. 1 and 3 only
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1, 3 and 4 only

In lysogeny the DNA integrates, is copied with the host chromosome and can later be induced. Immediate lysis belongs to the lytic cycle.

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Where does a newly budded influenza envelope mainly originate?

  1. A protein layer assembled entirely from capsid subunits
  2. The nuclear envelope enclosing the host chromosome
  3. Host lipid membrane containing viral proteins
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Host lipid membrane containing viral proteins

Budding incorporates a membrane carrying viral glycoproteins.

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Which order fits the HIV information pathway?

  1. RNA -> integrated RNA provirus -> DNA after budding
  2. RNA -> new RNA genomes with no DNA intermediate
  3. RNA -> DNA -> integrated provirus -> RNA/protein production
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RNA -> DNA -> integrated provirus -> RNA/protein production

This includes reverse transcription and integration.

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Which step is NOT part of the HIV replication cycle?

  1. Reverse transcription of viral RNA into DNA
  2. Integration of viral DNA into a host chromosome
  3. Budding from the host cell membrane
  4. Copying viral RNA directly into new RNA genomes
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Copying viral RNA directly into new RNA genomes

HIV copies its RNA into DNA first. New RNA genomes are transcribed from the integrated provirus by host RNA polymerase.

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Which circumstance directly permits reassortment?

  1. One non-segmented genome in one uninfected cell
  2. Two influenza strains replicating in separate cells only
  3. Two compatible segmented influenza strains co-infecting a cell
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Two compatible segmented influenza strains co-infecting a cell

Segments can be packaged into new combinations.

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After complete F-plasmid transfer and DNA synthesis, what is the usual result?

  1. The recipient receives only protein and remains permanently F-.
  2. Both donor and recipient carry an F plasmid.
  3. The donor loses its plasmid permanently.
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Both donor and recipient carry an F plasmid.

Replication restores double-stranded copies in both cells.

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Question 1 of 8

Discuss whether viruses are living

4 marks

Give a balanced, criteria-based discussion of whether viruses should count as living entities. Relate your answer to cell theory. [4]

Use properties on both sides rather than only a verdict.

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