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Questions and Answers
What is the viral DNA called after it integrates into the bacterial genome during the lysogenic cycle?
What is the viral DNA called after it integrates into the bacterial genome during the lysogenic cycle?
During the lysogenic cycle, bacterial cells do not carry a copy of the viral DNA.
During the lysogenic cycle, bacterial cells do not carry a copy of the viral DNA.
False
What mechanism describes the transfer of bacterial genes via bacteriophages?
What mechanism describes the transfer of bacterial genes via bacteriophages?
Transduction
The expression of viral genes during the lysogenic lifecycle may lead to the phenomenon known as ______.
The expression of viral genes during the lysogenic lifecycle may lead to the phenomenon known as ______.
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How can environmental factors like UV radiation affect a prophage?
How can environmental factors like UV radiation affect a prophage?
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Match the following components with their descriptions:
Match the following components with their descriptions:
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What are the two identical molecules that make up the genome of HIV?
What are the two identical molecules that make up the genome of HIV?
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HIV primarily infects T-helper cells through their CD4+ receptors.
HIV primarily infects T-helper cells through their CD4+ receptors.
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What is the first step in the viral replication process?
What is the first step in the viral replication process?
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In the lysogenic cycle, the infected bacterium immediately starts producing new virus particles.
In the lysogenic cycle, the infected bacterium immediately starts producing new virus particles.
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Name the bacterium commonly infected by bacteriophages.
Name the bacterium commonly infected by bacteriophages.
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The stage during the lytic cycle where new phage particles are produced is known as ______.
The stage during the lytic cycle where new phage particles are produced is known as ______.
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Match the following stages of the bacteriophage lytic cycle with their descriptions:
Match the following stages of the bacteriophage lytic cycle with their descriptions:
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Which of the following is a characteristic of the lytic cycle?
Which of the following is a characteristic of the lytic cycle?
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Bacteriophage Lambda can carry out only the lytic cycle.
Bacteriophage Lambda can carry out only the lytic cycle.
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What is produced by the viral gene during the release stage of the lytic cycle?
What is produced by the viral gene during the release stage of the lytic cycle?
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What key factor did Robert Koch contribute to microbiology?
What key factor did Robert Koch contribute to microbiology?
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Viruses are considered living organisms because they can reproduce independently.
Viruses are considered living organisms because they can reproduce independently.
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What is the role of reverse transcriptase in a retrovirus?
What is the role of reverse transcriptase in a retrovirus?
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The __________ virus obtains its envelope from the host cell membrane.
The __________ virus obtains its envelope from the host cell membrane.
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Match the following virus types with their characteristics:
Match the following virus types with their characteristics:
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What is typically required to promote microbial growth in a laboratory setting?
What is typically required to promote microbial growth in a laboratory setting?
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When a prophage is activated, it immediately enters the lytic cycle.
When a prophage is activated, it immediately enters the lytic cycle.
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What can activate a prophage?
What can activate a prophage?
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Study Notes
Virus Replication Process
- Infection involves three main steps: attachment, entry, and uncoating of the virus.
- Viral genes undergo transcription to initiate replication.
- New nucleic acid is generated, followed by translation for protein synthesis.
- Newly formed virus particles are assembled before release of mature virions.
Bacteriophages
- Bacteriophages infect bacteria, with lytic and lysogenic life cycles.
- Lytic cycle leads to host cell lysis, releasing virus particles.
- Lysogenic cycle incorporates viral genetic material into the host genome, resulting in latent infections.
- Example: Bacteriophage Lambda can perform both lytic and lysogenic cycles.
Lytic Cycle Stages
- Attachment: Capsid components bind specifically to bacterial cell wall receptors.
- Penetration: Viral enzymes digest cell wall; viral DNA is injected into the bacterium.
- Biosynthesis: Host’s biosynthetic machinery is hijacked for viral DNA and protein production.
- Maturation: Assembly of DNA and capsid proteins to form new phage particles.
- Release: Lysozyme disrupts the bacterial cell wall, releasing new phage particles and killing the host.
Lysogenic Cycle Characteristics
- After attachment and penetration, viral DNA integrates into the bacterial genome, becoming a prophage.
- Prophage replicates with the host DNA, passed to daughter cells.
- External factors like UV radiation can trigger prophage excision, leading to a lytic cycle.
- DNA from the host may be packaged into viral particles, enabling gene transfer through transduction.
Phage Conversion
- Virus genes expressed during lysogeny can alter host cells, a phenomenon called phage conversion.
- Example: Vibrio cholerae becomes pathogenic due to viral integration of the cholera toxin gene.
Human Immunodeficiency Virus (HIV)
- HIV is a complex retrovirus with two identical positive single-stranded RNA molecules.
- Originated in Western Africa; spread globally after transmission from primates to humans.
- Targets CD4+ T-helper cells in the human immune system, allowing viral entry.
- HIV genetic material includes genes for essential viral enzymes: reverse transcriptase, protease, and integrase.
Microbial Growth
- Microorganisms are omnipresent in the environment but often not visible.
- Growth is influenced by various factors, which can be manipulated to promote or inhibit microbial growth.
Koch's Postulates
- Established by Robert Koch, linking microorganisms to specific diseases.
- Evidence includes successful transmission of Bacillus anthracis to healthy mice.
- His work laid the foundation for understanding the relationship between pathogens and disease.
Further Study
- Recommended videos for visual understanding of virus replication strategies and an overview of viruses.
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