79. RETROVIRUS REPLICATIVE CYCLE Flashcards
1
Q
- 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
2
Q
- 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
3
Q
- What is the Retrovirus Dogma?
A
Viral RNA
↧
DNA
↧
RNA
↧
Viral Protein
4
Q
- What are the 6 Stages of the Retrovirus replicative cycle?
A
- Attachment and Entry
- Reverse Transcriptase
- Integrase
- Transcription
- Protease
- Release from the Host Cell
5
Q
- What happens during: Attachment and Entry?
A
- the glycoprotein of the Retrovirus
- bind to the receptor of the host cell
6
Q
- 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)
7
Q
- 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
8
Q
- 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
9
Q
- What are the 2 functions of the RNA molecules in the Retrovirus Replicative Cycle?
A
- the RNA molecules in the virus have 2 functions
- THEY FUNCTION AS MRNA:
- this allows for Viral proteins to be made - THEY FUNCTION AS GENOMES:
- this allows for new virus particles to be released from
the cell
10
Q
- 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
11
Q
- Provide labels for numbers 1-5.
A
- Glycoprotein
- Viral Envelope
- Capsid
- Two identical strands of RNA
- Reverse Transcriptase
12
Q
- 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
13
Q
- What are the Replicative Cycles of Bacteriophages?
A
- The Lytic Cycle
- results in the destruction of the Host cell
- this is known as Lysis - The Lysogenic Cycle
- the Host cell is not destroyed
14
Q
- 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
15
Q
- Define: Virulent Phages.
A
- these are Bacteriophages that only reproduce by using
the Lytic Cycle
16
Q
- 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
- Label this diagram of a Bacteriophage.
A
- Head
- Tail
- Tail Fibres
18
Q
- Label the Lytic Cycle Diagram.
A
- ATTACHMENT
- ENTRY OF THE PHAGE INTO THE HOST CELL
- the host cell is degraded - PRODUCTION OF THE GENOMES OF THE VIRUS
- production of the proteins of the virus - ASSEMBLY
- of the viral genomes and proteins - RELEASE OF THE PHAGE FROM THE HOST CELL
- this destroys the host cell
19
Q
- 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
- Define: Prophage.
A
- this is the DNA from the Viral Bacteriophage
- that has been integrated into the Host Cell
21
Q
- 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
- 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
- Define: Temperate Phages.
A
- these are Bacteriophages
- they replicate using both the Lytic and the Lysogenic
Cycle
24
Q
- Does this diagram make sense?
A
- yes
25
25. List 4 characteristics of the Lytic Cycle.
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
26. List 4 characteristics of the Lysogenic Cycle.
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
27. Do viruses consist of Cells?
- no
- this means that they do not fit the definition of living
organisms
28
28. What is the Origin of Viruses?
- they originate from Nucleic Acid Fragments
- these are released from organisms with cells
29
29. List some possible sources of Viral Genomes.
- Plasmids
- Bacterial DNA
- Yeast DNA
- Transposons
30
30. Define: Transposons.
- these are small DNA segments
- they are mobile
