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MED 109- BIOLOGY II > 79. RETROVIRUS REPLICATIVE CYCLE > Flashcards

79. RETROVIRUS REPLICATIVE CYCLE Flashcards

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1
Q
  1. Define: Retroviruses.
A
  • they are single stranded RNA viruses
  • they go against the usual method of the transfer of
    genetic information

THEY MAKE USE OF REVERSE TRANSCRIPTASE:
- this is an enzyme found in the RNA Virus
- it converts the viral RNA into DNA

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2
Q
  1. What is an example of a Retrovirus?
A
  • HIV
  • this is the Human Immuno Deficiency Virus

THIS VIRUS:
- causes AIDS
- this stands for Acquired Immuno Deficiency Syndrome

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3
Q
  1. What is the Retrovirus Dogma?
A

Viral RNA
↧
DNA
↧
RNA
↧
Viral Protein

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4
Q
  1. What are the 6 Stages of the Retrovirus replicative cycle?
A
  1. Attachment and Entry
  2. Reverse Transcriptase
  3. Integrase
  4. Transcription
  5. Protease
  6. Release from the Host Cell
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5
Q
  1. What happens during: Attachment and Entry?
A
  • the glycoprotein of the Retrovirus
  • bind to the receptor of the host cell
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6
Q
  1. What happens during: Reverse Transcriptase?
A
  • the viral RNA is exposed to Reverse Transcriptase
  • this is an enzyme found in the virus

THE REVERSE TRANSCRIPTASE COVERTS:
- the RNA
- into copies of DNA (cDNA)

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7
Q
  1. What happens during: Integrase?
A
  • this is an enzyme found in the Virus
  • it will integrate the Viral Genome into the Host Cell’s
    Genome

THE CDNA OF THE RETROVIRUS:
- is inserted into the host genome
- it is inserted as a Provirus
- this process happens at Random

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8
Q
  1. What happens during: Transcription?
A
  • the RNA Polymerase will transcribe the DNA in the
    Provirus
  • into RNA molecules

RNA POLYMERASE:
- is an enzyme found in the Host Cell

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9
Q
  1. What are the 2 functions of the RNA molecules in the Retrovirus Replicative Cycle?
A
  • the RNA molecules in the virus have 2 functions
  1. THEY FUNCTION AS MRNA:
    - this allows for Viral proteins to be made
  2. THEY FUNCTION AS GENOMES:
    - this allows for new virus particles to be released from
    the cell
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10
Q
  1. What happens during: Protease?
A
  • this is an enzyme found in the virus
  • it cuts the Polypeptide in the virus
  • it assembled the protein particles
  • it releases them from the cell as a new virus

THE VIRAL POLYPEPTIDE:
- was produced by translation

PROTEASE:
- is kept in a capsid
- it is a large target for many anti-viral medications

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11
Q
  1. Provide labels for numbers 1-5.
A
  1. Glycoprotein
  2. Viral Envelope
  3. Capsid
  4. Two identical strands of RNA
  5. Reverse Transcriptase
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12
Q
  1. Provide a label for number 6.
A
  • the Provirus is integrated into the host cell genome
  • it is inserted into the host cell’s chromosomes
  • it will be converted to RNA
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13
Q
  1. What are the Replicative Cycles of Bacteriophages?
A
  1. The Lytic Cycle
    - results in the destruction of the Host cell
    - this is known as Lysis
  2. The Lysogenic Cycle
    - the Host cell is not destroyed
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14
Q
  1. In the Lytic Cycle, how does the Host Cell Lysis occur?
A
  • the Host Cell’s membrane will break open
  • this releases the new phages
  • these are known as the Progeny
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15
Q
  1. Define: Virulent Phages.
A
  • these are Bacteriophages that only reproduce by using
    the Lytic Cycle
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16
Q
  1. How do Bacteria defend themselves against Bacteriophages?
A
  • they have specific Bacterial Restriction Enzymes
  • these will recognise the DNA of a certain
    Bacteriophage
  • they will cut up the DNA of this phage

THIS IS NEEDED:
- since Bacteria do not have an immune system
- they are unicellular

17
Q
  1. Label this diagram of a Bacteriophage.
A
  1. Head
  2. Tail
  3. Tail Fibres
18
Q
  1. Label the Lytic Cycle Diagram.
A
  1. ATTACHMENT
  2. ENTRY OF THE PHAGE INTO THE HOST CELL
    - the host cell is degraded
  3. PRODUCTION OF THE GENOMES OF THE VIRUS
    - production of the proteins of the virus
  4. ASSEMBLY
    - of the viral genomes and proteins
  5. RELEASE OF THE PHAGE FROM THE HOST CELL
    - this destroys the host cell
19
Q
  1. What happens during the Lysogenic Cycle?
A
  • the Bacteriophage genome will replicate
  • it does this without destroying the Host Cell

THE DNA OF THE BACTERIOPHAGE:
- will be incorporated into the Host Cell’s Chromosomes

20
Q
  1. Define: Prophage.
A
  • this is the DNA from the Viral Bacteriophage
  • that has been integrated into the Host Cell
21
Q
  1. What happens when a Host Cell with a Prophage in it undergoes Cell Division?
A
  • the Bacteriophage DNA will be copied
  • it will be passed down to the Host Cell’s daughter cells
22
Q
  1. How does a Bacteriophage switch from a Lysogenic Mode of Replication to a Lytic one?
A
  • an environmental signal can trigger the Bacteriophage
    genome to exit the Bacterial Chromosome
23
Q
  1. Define: Temperate Phages.
A
  • these are Bacteriophages
  • they replicate using both the Lytic and the Lysogenic
    Cycle
24
Q
  1. Does this diagram make sense?
A
  • yes
25
Q
  1. List 4 characteristics of the Lytic Cycle.
A
  1. VIRULENT OR TEMPERATE PHAGES
    - will undergo this kind of replication
  2. DESTRUCTION OF THE HOST DNA
  3. PRODUCTION OF NEW PHAGES
  4. LYSIS OF THE HOST CELL
    • this causes the release of Progeny Phages
26
Q
  1. List 4 characteristics of the Lysogenic Cycle.
A
  1. TEMPERATE PHAGES
    - will undergo this kind of replication
  2. THE GENOME OF THE BACTERIOPHAGE
    - will be integrated into the Bacterial Chromosome
    - it is integrated as a Prophage
  3. THE PROPHAGE CAN BE REPLICATED
    - it is passed onto the Bacterial daughter cells
    - this happens during cell division
  4. THE PROPHAGE CAN LEAVE THE BACTERIAL
    CHROMOSOME
    • this is caused by an environmental change
    • this will initiate a Lytic Cycle
27
Q
  1. Do viruses consist of Cells?
A
  • no
  • this means that they do not fit the definition of living
    organisms
28
Q
  1. What is the Origin of Viruses?
A
  • they originate from Nucleic Acid Fragments
  • these are released from organisms with cells
29
Q
  1. List some possible sources of Viral Genomes.
A
  • Plasmids
  • Bacterial DNA
  • Yeast DNA
  • Transposons
30
Q
  1. Define: Transposons.
A
  • these are small DNA segments
  • they are mobile

MED 109- BIOLOGY II (90 decks)

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