p.8
Bacteriophages and Their Mechanisms
How do bacteriophages reproduce?
By using some or all of the cellular machinery of the host cell.
p.3
Structure and Components of Viruses
What are the main components of viruses?
Nucleic acids (DNA or RNA) and proteins.
p.17
Viral Reproductive Cycles
Where are viral glycoproteins synthesized in the host cell?
In the rough endoplasmic reticulum (ER) and glycosylated by the Golgi apparatus.
p.15
Viral Reproductive Cycles
What happens during the budding process?
The host cell membrane surrounds the nucleocapsid and pinches off to form the viral envelope.
p.22
Variation in Viral Genomes: Antigenic Drift and Shift
How does antigenic shift differ from antigenic drift?
Antigenic shift involves major changes, while antigenic drift involves minor changes over time.
p.18
Human Immunodeficiency Virus (HIV) Overview
What is a key characteristic of retroviruses like HIV?
They reverse transcribe their RNA into DNA.
p.12
Influenza Virus Characteristics and Infection
What are the two main glycoproteins found on the influenza viral envelope?
Haemagglutinin and neuraminidase.
p.12
Influenza Virus Characteristics and Infection
What other proteins and enzymes does the influenza viral genome code for?
RNA-dependent RNA polymerase, capsomeres, accessory proteins, etc.
p.15
Viral Reproductive Cycles
How does neuraminidase facilitate the release of virions?
By cleaving the terminal sialic acid residues, thereby freeing the virions.
p.9
Bacteriophages and Their Mechanisms
What is a virulent phage?
A phage that reproduces only via the lytic cycle.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic shift?
A major change to the virus structure that creates new subtypes of influenza with new combinations of glycoproteins.
p.16
Human Immunodeficiency Virus (HIV) Overview
What is the primary function of T-helper cells in the immune system?
They are involved in the immune response and are targeted by HIV.
p.4
Structure and Components of Viruses
What serves as the viral genome?
The central core of nucleic acid.
p.5
Structure and Components of Viruses
What types of biomolecules are found in naked viruses?
Proteins and nucleic acids.
p.8
Bacteriophages and Their Mechanisms
What are bacteriophages?
Viruses that infect bacteria.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
Why is genetic reassortment undesirable?
It may produce new human influenza viruses with glycoproteins from avian or swine viruses, which the human immune system has not encountered.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
What is a consequence of antigenic drift in influenza viruses?
Individuals can be infected by the same virus again.
p.18
Viral Reproductive Cycles
What is the primary focus of the reproduction cycle of HIV?
The process by which HIV replicates within host cells.
p.12
Influenza Virus Characteristics and Infection
What is the role of haemagglutinin in the influenza virus?
It mediates the attachment of the virus to the target cell and entry of the viral genome into the cell.
p.17
Viral Reproductive Cycles
What happens after HIV attaches to the CD4 receptor?
The viral envelope fuses with the host cell membrane, releasing the nucleocapsid into the cytoplasm.
p.17
Viral Reproductive Cycles
What is the role of reverse transcriptase in the HIV reproductive cycle?
It converts single-stranded RNA into double-stranded DNA.
p.17
Viral Reproductive Cycles
What is a provirus in the context of HIV?
Integrated viral DNA that remains silent in the host DNA.
p.17
Viral Reproductive Cycles
What triggers the transcription of the provirus in HIV-infected T-helper cells?
Activation of the host T-helper cell during an immune response.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
What causes antigenic shift?
Genetic reassortment between different types of influenza viruses, often facilitated by species like pigs that can be infected by multiple types.
p.9
Bacteriophages and Their Mechanisms
What happens during the replication phase of the T4 phage cycle?
The phage uses the host's DNA replication machinery to replicate its genome and synthesize viral proteins.
p.3
Viral Reproductive Cycles
What type of parasites are viruses classified as?
Obligate intracellular parasites.
p.1
Structure and Components of Viruses
What are the structural components of viruses?
Including enveloped viruses and bacteriophages.
p.22
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic shift in the influenza virus?
A major change in the virus's surface proteins, leading to new strains.
p.15
Viral Reproductive Cycles
How do viruses obtain their viral envelopes?
By budding from host cell membranes.
p.7
Challenges to the Cell Theory by Viruses
What are the three principles of the cell theory?
1. All living organisms are composed of one or more cells. 2. The cell is the smallest and most basic unit of life. 3. Cells grow from pre-existing cells.
p.2
Challenges to the Cell Theory by Viruses
Are viruses considered living organisms?
No, viruses are not classified as living organisms.
p.24
Influenza Virus Characteristics and Infection
What happens to the respiratory tract due to influenza infection?
Death of epithelial cells impairs functions like mucus clearance.
p.7
Viral Reproductive Cycles
What is the first step in the viral reproductive cycle?
Attachment/Adsorption, where the virus binds to specific receptors on the host cell.
p.10
Viral Reproductive Cycles
What occurs after the phage DNA is replicated?
Phage proteins are produced and mature phages are assembled.
p.11
Bacteriophages and Their Mechanisms
What type of phage is the lambda (λ) phage?
A temperate phage, as it reproduces via both lytic and lysogenic cycles.
p.2
Influenza Virus Characteristics and Infection
What is a characteristic of the influenza virus?
It infects epithelial cells of the respiratory tract.
p.7
Viral Reproductive Cycles
What materials does the host cell provide for viral replication?
Nucleotides, ribosomes, tRNAs, amino acids, ATP, and other raw materials.
p.25
Human Immunodeficiency Virus (HIV) Overview
What happens when T-helper cells are activated?
They release cytokines that stimulate the activity of macrophages, killer T cells, and B cells, which produce antibodies.
p.4
Structure and Components of Viruses
How do some viruses inject their nucleic acid into host cells?
By penetrating the cell membrane or injecting it into the cytoplasm.
p.10
Viral Reproductive Cycles
What is the role of the capsid during phage infection?
It remains at the cell surface while viral DNA enters the host cell.
p.11
Viral Reproductive Cycles
What triggers the induction of the prophage?
Adverse external stimuli such as ionising radiation, UV radiation, toxic chemicals, or lack of nutrients.
p.22
Variation in Viral Genomes: Antigenic Drift and Shift
What can antigenic shift result in?
The emergence of new influenza virus strains that can evade immunity.
p.18
Human Immunodeficiency Virus (HIV) Overview
What is the significance of the reproduction cycle in understanding HIV?
It helps in developing treatments and understanding the virus's behavior.
p.14
Viral Reproductive Cycles
What forms a complex that is transported into the nucleus during influenza replication?
Accessory proteins and viral RNA.
p.14
Viral Reproductive Cycles
What enzyme catalyzes the replication of single-stranded RNA in the nucleus?
RNA-dependent RNA polymerase.
p.5
Structure and Components of Viruses
How are enveloped viruses classified?
As viruses that have a lipid envelope.
p.5
Structure and Components of Viruses
What are naked viruses?
Viruses that do not have a lipid envelope.
p.24
Influenza Virus Characteristics and Infection
What determines host specificity for the influenza virus?
The specificity between the viral glycoprotein (haemagglutinin) and the sialic acid receptor on epithelial cells.
p.5
Structure and Components of Viruses
What types of biomolecules are found in enveloped viruses?
Phospholipids, cholesterols, and viral glycoproteins.
p.6
Challenges to the Cell Theory by Viruses
Do viruses display characteristics of living organisms when outside a host cell?
No, they do not display many characteristics such as reproduction and metabolism.
p.19
Mechanisms of Viral Entry into Host Cells
What is a key difference in the entry step between influenza virus and HIV?
Influenza virus enters cells via endocytosis, while HIV fuses directly with the host cell membrane.
p.14
Viral Reproductive Cycles
What is the final step for newly-formed nucleocapsids after assembly?
They leave the nucleus and are transported to the exit point at the cell surface membrane.
p.9
Bacteriophages and Their Mechanisms
What role does lysozyme play in the exit/release phase of the T4 phage?
It hydrolyzes the peptidoglycan cell wall of the host bacterium, leading to cell lysis and release of new phages.
p.26
Human Immunodeficiency Virus (HIV) Overview
What happens during the activation of host cells infected by HIV?
Transcription of viral DNA into mRNA occurs, which is then translated into viral proteins.
p.25
Human Immunodeficiency Virus (HIV) Overview
How do T-helper cells become activated?
They recognize antigens presented by antigen presenting cells (APCs) on Class II MHC molecules with the help of CD4 receptors.
p.26
Human Immunodeficiency Virus (HIV) Overview
What role does HIV protease play in the viral life cycle?
It processes other HIV proteins into their functional forms.
p.12
Influenza Virus Characteristics and Infection
How many segments does the influenza viral genome consist of?
8 separate segments of single-stranded RNA.
p.3
Challenges to the Cell Theory by Viruses
What are viruses classified as?
The simplest biological systems.
p.12
Influenza Virus Characteristics and Infection
What function does neuraminidase serve in the influenza virus life cycle?
It is involved in the release of newly formed influenza viruses from infected cells.
p.3
Structure and Components of Viruses
What are enveloped viruses?
Viruses that have an additional membrane outside the protein coat.
p.9
Bacteriophages and Their Mechanisms
What begins the eclipse period in the T4 phage reproductive cycle?
The entry of viral DNA into the host bacterium.
p.10
Viral Reproductive Cycles
What marks the beginning of the eclipse period in a lytic cycle?
The entry of viral DNA into the host cell.
p.25
Human Immunodeficiency Virus (HIV) Overview
What are T-helper cells?
A sub-group of lymphocytes involved in activating and directing other immune cells.
p.6
Challenges to the Cell Theory by Viruses
What happens to viruses when they infect a host cell?
They acquire the ability to display characteristics of living organisms by taking over the host's cellular machinery.
p.10
Viral Reproductive Cycles
When does the eclipse period end?
When mature phages appear in the host cell.
p.1
Challenges to the Cell Theory by Viruses
How do viruses challenge the cell theory?
They challenge concepts of what is considered living.
p.11
Mechanisms of Viral Entry into Host Cells
How does the λ phage attach and enter the host bacterium?
The method of attachment and entry of the viral DNA is similar to the T4 phage.
p.10
Viral Reproductive Cycles
What is the burst/rise period?
The time from the end of the latent period until all phages are released.
p.7
Viral Reproductive Cycles
What happens during the assembly and maturation phase of viral reproduction?
Viral nucleic acid and proteins self-assemble into new nucleocapsids.
p.26
Human Immunodeficiency Virus (HIV) Overview
What is required for HIV to spread throughout the body?
The HIV reproductive cycle must not be interrupted by appropriate treatment.
p.16
Human Immunodeficiency Virus (HIV) Overview
What type of genetic material does the HIV genome consist of?
Two copies of linear, single-stranded RNA.
p.2
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic shift?
A significant change in viral antigens due to reassortment of genetic material.
p.8
Structure and Components of Viruses
What is a contractile sheath in complex phages like T4?
A structure that surrounds the tail and contracts during infection of the bacterium.
p.9
Bacteriophages and Their Mechanisms
What are the two alternative mechanisms by which phages reproduce?
Lytic cycle and lysogenic cycle.
p.24
Influenza Virus Characteristics and Infection
What type of cells does the influenza virus target in mammals?
Epithelial cells of the respiratory tract.
p.7
Challenges to the Cell Theory by Viruses
How do viruses challenge the cell theory?
Viruses are non-cellular, smaller and more basic than cells, yet display some characteristics of life.
p.16
Human Immunodeficiency Virus (HIV) Overview
How is HIV transmitted?
Through the transfer of body fluids, such as blood or semen.
p.2
Viral Reproductive Cycles
What is a key feature of a viral reproductive cycle?
It includes specific stages such as attachment, penetration, replication, assembly, and release.
p.26
Human Immunodeficiency Virus (HIV) Overview
Why does HIV have a high rate of mutation?
Because HIV reverse transcriptase is error-prone.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
What happens when different types of influenza viruses infect the same pig host cell?
The progeny viruses may contain RNA segments from different virus types due to genetic reassortment.
p.17
Viral Reproductive Cycles
What completes the maturation of new HIV viruses after their release?
HIV protease cuts viral polyproteins to form structural and enzymatic proteins.
p.7
Viral Reproductive Cycles
What happens during the penetration/entry phase of viral reproduction?
The viral genome enters the host cell, with mechanisms varying by virus type and host cell.
p.6
Challenges to the Cell Theory by Viruses
What are viruses classified as?
Strict obligate intracellular parasites.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
What is the risk associated with new types of human influenza viruses?
They may be able to transmit between humans, potentially leading to a global pandemic.
p.10
Viral Reproductive Cycles
What is the latent period in a lytic cycle?
The time from the start of infection until mature phages are released.
p.1
Viral Reproductive Cycles
What is the reproductive cycle of bacteriophages that reproduce via the lytic cycle?
An example is the T4 phage.
p.11
Bacteriophages and Their Mechanisms
What is a lysogen?
An infected bacterium that harbors the prophage.
p.6
Challenges to the Cell Theory by Viruses
How do dormant viruses respond within a host cell?
They can respond to external signals to trigger reproduction.
p.15
Viral Reproductive Cycles
What role do viral glycoproteins play in the budding process?
They are incorporated into the host cell membranes prior to budding.
p.15
Viral Reproductive Cycles
What is the function of haemagglutinin in the release of new viruses?
It may attach to adjacent receptors containing sialic acid, preventing the release of new viruses.
p.5
Structure and Components of Viruses
How do viruses acquire their lipid envelope?
Through a process called budding when newly-formed viruses leave the host cell.
p.5
Structure and Components of Viruses
What are glycoprotein spikes?
Viral proteins incorporated into the lipid envelope that help attach the virus to specific host cell receptors.
p.2
Structure and Components of Viruses
What are the general features of viruses?
Viruses have unique structural components and reproductive cycles.
p.6
Challenges to the Cell Theory by Viruses
What characteristics define a living organism?
Order, homeostasis, response to stimuli, heredity, metabolism, reproduction, and evolution.
p.19
Mechanisms of Viral Entry into Host Cells
What is a similarity in the entry step between influenza virus and HIV?
Both viruses utilize specific receptors on host cells to facilitate entry.
p.13
Influenza Virus Characteristics and Infection
How is the influenza virus primarily spread to host animals?
Through airborne transmission via aerosolized viral particles.
p.24
Influenza Virus Characteristics and Infection
What are some symptoms caused by influenza infection?
Fever, sore throat, muscle pains, coughing, and in serious cases, pneumonia.
p.25
Human Immunodeficiency Virus (HIV) Overview
What is an antigen?
A substance that triggers an immune response, leading to the production of antibodies.
p.13
Viral Reproductive Cycles
How does the influenza virus enter the host cell?
By endocytosis, forming an endocytic vesicle.
p.2
Human Immunodeficiency Virus (HIV) Overview
What is the role of T-helper cells in HIV infection?
HIV targets and destroys T-helper cells, compromising the immune system.
p.13
Viral Reproductive Cycles
What happens to the capsid coat during the entry of the influenza virus?
It is enzymatically removed, releasing viral RNA and proteins into the cytoplasm.
p.23
Viral Diseases and Their Impact on Host Cells
What symptoms of viral infections are caused by the body's immune response?
Symptoms such as fever and aches.
p.23
Variation in Viral Genomes: Antigenic Drift and Shift
How does increased variation in viral genomes complicate eradication efforts?
It leads to the emergence of new viral strains that may evade immune responses and treatments.
p.5
Structure and Components of Viruses
What is a lipid envelope in viruses?
A lipid membrane composed of phospholipids and cholesterols, often derived from the host cell membrane.
p.16
Human Immunodeficiency Virus (HIV) Overview
What disease does the Human Immunodeficiency Virus (HIV) cause?
Acquired Immunodeficiency Syndrome (AIDS).
p.4
Structure and Components of Viruses
What is the central core of a virus composed of?
Nucleic acid surrounded by a protein capsid coat.
p.3
Structure and Components of Viruses
What are naked viruses?
Viruses that do not have a membrane.
p.7
Challenges to the Cell Theory by Viruses
Do new viruses grow from pre-existing viruses?
No, they do not undergo cell division and instead infect host cells to synthesize new viral components.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
Which viral glycoproteins are affected by antigenic drift?
Haemagglutinin and neuraminidase.
p.4
Structure and Components of Viruses
What are the possible forms of nucleic acid in viruses?
Linear or circular, single- or double-stranded, and can exist as single or multiple molecules.
p.25
Human Immunodeficiency Virus (HIV) Overview
What role do T-helper cells play in the immune system?
They activate and direct other immune cells, making them crucial for immune response.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
Why might antibodies from a previous influenza infection be ineffective against a new strain?
Due to mutations that alter the glycoproteins slightly.
p.1
Variation in Viral Genomes: Antigenic Drift and Shift
What types of genomes do viruses have?
Viral genomes can be DNA/RNA, single/double-stranded, linear/circular, and may or may not have introns.
p.6
Challenges to the Cell Theory by Viruses
Do viruses carry out metabolism independently?
No, they cannot generate usable forms of energy like ATP on their own.
p.16
Human Immunodeficiency Virus (HIV) Overview
What enzyme does a retrovirus carry, and what is its function?
Reverse transcriptase; it catalyzes the synthesis of DNA from an RNA template.
p.7
Viral Reproductive Cycles
How do naked and enveloped viruses exit the host cell?
Naked viruses usually exit via lysis of the host cell, while enveloped viruses exit through budding, often resulting in the death of the host cell.
p.26
Human Immunodeficiency Virus (HIV) Overview
What types of medications are currently used to contain HIV infection?
Inhibitors of reverse transcriptase and HIV protease.
p.25
Human Immunodeficiency Virus (HIV) Overview
What is the consequence of T-helper cell death due to HIV infection?
It impairs the immune system, leading to AIDS and inability to defend against opportunistic infections.
p.8
Structure and Components of Viruses
Do all phages have a base plate and tail fibres?
No, not all phages have these structures; others may use different structures on the capsid for binding.
p.14
Viral Reproductive Cycles
What happens to the replicated complementary RNA strand in the nucleus?
It either stays to replicate more viral genome or is exported to the cytoplasm for protein translation.
p.26
Human Immunodeficiency Virus (HIV) Overview
How can the insertion of viral DNA into the host genome lead to cancer?
It can disrupt tumor suppressive genes or convert proto-oncogenes to oncogenes.
p.21
Variation in Viral Genomes: Antigenic Drift and Shift
Why are pigs significant in the context of antigenic shift?
Pigs can be infected by avian, human, and swine influenza viruses, allowing for genetic reassortment.
p.13
Influenza Virus Characteristics and Infection
What receptor does the influenza virus bind to on host cells?
Sialic acid on the surface of epithelial cells.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
What happens to a person's immunity after recovering from an influenza virus infection?
They develop antibodies specific to the glycoproteins of that virus.
p.23
Viral Diseases and Their Impact on Host Cells
What does eradication of viral diseases refer to?
The permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
What seasonal phenomenon is caused by antigenic drift?
Seasonal flu epidemics occurring every winter.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic drift in influenza viruses?
It results in influenza viruses with slightly-modified glycoproteins.
p.13
Viral Reproductive Cycles
What is the function of the endosome in the context of influenza virus entry?
It sorts substances taken in through endocytosis and has an acidic pH that aids in viral entry.
p.9
Bacteriophages and Their Mechanisms
How does the T4 phage penetrate the bacterial cell wall?
By contracting the contractile sheath of the tail, driving the hollow tube into the host bacterium.
p.14
Viral Reproductive Cycles
Where are viral glycoproteins synthesized?
In the rough endoplasmic reticulum (ER) and glycosylated by the Golgi apparatus.
p.26
Human Immunodeficiency Virus (HIV) Overview
What effect does a more active viral promoter have on proto-oncogenes?
It may cause over-expression, converting proto-oncogenes into oncogenes.
p.3
Viral Reproductive Cycles
How do viruses reproduce?
By invading living host cells and hijacking their cellular machinery.
p.14
Viral Reproductive Cycles
Where are viral glycoproteins inserted in the host cell?
Into the cell surface membrane at the exit point for viral release.
p.9
Bacteriophages and Their Mechanisms
What is formed during the assembly and maturation phase of the T4 phage?
Mature phage particles are formed as protein components assemble around the viral genome.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
How does variation in the viral genome arise?
It mostly arises due to mutations during the replication of the viral genome.
p.13
Influenza Virus Characteristics and Infection
What triggers the entry of the influenza virus into the host cell?
A conformational change of the receptor after binding.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
What is the approximate error rate of influenza RNA-dependent RNA polymerase?
1 per 10^3 - 10^5 nucleotides incorporated.
p.23
Viral Diseases and Their Impact on Host Cells
How do viral infections generally cause diseases?
By resulting in the death of host cells, leading to damage in host tissue and disruption of tissue functions.
p.13
Viral Reproductive Cycles
What role does haemagglutinin play in the entry of the influenza virus?
It facilitates the fusion of the viral envelope with the endosomal membrane.
p.2
Variation in Viral Genomes: Antigenic Drift and Shift
How does variation in viral genomes arise?
Through processes like antigenic drift and antigenic shift.
p.25
Human Immunodeficiency Virus (HIV) Overview
How does HIV target T-helper cells?
By binding glycoprotein gp120 to the specific CD4 receptor on T-helper cells.
p.26
Human Immunodeficiency Virus (HIV) Overview
What are the ultimate challenges in controlling the AIDS epidemic?
Developing medications to eradicate HIV and creating a vaccine to prevent new infections.
p.13
Viral Reproductive Cycles
What causes the conformational change in haemagglutinin during viral entry?
The low pH within the endosome.
p.16
Human Immunodeficiency Virus (HIV) Overview
What components are found in the structure of HIV?
Proteins, enzymes like reverse transcriptase and integrase, a viral envelope, and glycoproteins.
p.20
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic drift?
A gradual process where mutations in viral RNA lead to changes in glycoproteins over time.
p.10
Viral Reproductive Cycles
What happens during the eclipse period?
Infectious phages are not yet assembled inside the host cell.
p.2
Bacteriophages and Their Mechanisms
What is the lytic cycle in bacteriophages?
A reproductive cycle where the virus replicates and causes the host cell to burst.
p.26
Human Immunodeficiency Virus (HIV) Overview
What is the significance of gp120 in HIV?
Different strains of HIV have slightly altered gp120, making antibodies against earlier strains ineffective.
p.2
Bacteriophages and Their Mechanisms
What is the lysogenic cycle in bacteriophages?
A reproductive cycle where the viral DNA integrates into the host genome and replicates with it.
p.4
Structure and Components of Viruses
What are capsomeres?
Protein subunits that make up the capsid coat.
p.24
Influenza Virus Characteristics and Infection
Who is at high risk for severe illness from influenza?
Children under age two, adults over age 65, and people with chronic lung diseases or weakened immune systems.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
What is the error rate of HIV reverse transcriptase?
1 per 1700 nucleotides incorporated.
p.23
Viral Reproductive Cycles
What happens to host cells during viral replication?
They are unable to synthesize essential proteins, leading to reduced cellular functions and cell death.
p.2
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic drift?
A gradual change in viral antigens due to mutations.
p.23
Implications of Viral Infections on the Immune System
How do viral glycoproteins affect the immune response?
They may cause infected host cells to be recognized as foreign, leading to their destruction by immune cells.
p.16
Human Immunodeficiency Virus (HIV) Overview
What is integrated into the host DNA after reverse transcription?
The DNA produced by reverse transcription.
p.8
Bacteriophages and Their Mechanisms
What is the function of tail fibres in bacteriophages?
They are involved in the attachment of the phage to specific receptors on the bacterial cell.
p.1
Viral Diseases and Their Impact on Host Cells
How do viruses like HIV and influenza cause diseases in humans?
By disrupting host tissue and functions.
p.11
Viral Reproductive Cycles
What is the lysogenic cycle in relation to the lambda (λ) phage?
It involves the replication of only the phage genome without reproducing the entire phage particle or destroying the host bacterium.
p.24
Influenza Virus Characteristics and Infection
Why might certain influenza subtypes have high lethality?
Due to massive immune responses triggered by high levels of viral reproduction.
p.7
Viral Reproductive Cycles
What occurs during the replication phase of the viral reproductive cycle?
The virus uses host cell machinery to produce new viral components, including replication of the viral genome and expression of viral genes.
p.4
Structure and Components of Viruses
What is the function of the capsid coat?
To protect the nucleic acid, attach to host cell receptors, and enable penetration of the host cell membrane.
p.23
Viral Reproductive Cycles
What role do host cells play in viral replication?
Viruses use the host cellular machinery for replication, inhibiting normal DNA, RNA, and protein synthesis.
p.11
Viral Reproductive Cycles
What is a prophage?
The integrated viral DNA within the host bacterium's chromosome.
p.24
Implications of Viral Infections on the Immune System
Why are antibiotics sometimes prescribed for the common flu?
To prevent or treat secondary bacterial infections, even though the flu is caused by a virus.
p.8
Bacteriophages and Their Mechanisms
What role does the tail of a bacteriophage play?
It contains a hollow tube through which viral DNA enters the host bacterium.
p.11
Viral Reproductive Cycles
What role does the repressor protein play in the lysogenic cycle?
It prevents the transcription of most of the other prophage genes, keeping the phage genome mostly silent.
p.23
Implications of Viral Infections on the Immune System
What are cytokines?
Small proteins that function as signaling molecules between cells of the immune system, triggering inflammation and regulating the immune response.
p.1
Variation in Viral Genomes: Antigenic Drift and Shift
What causes variation in viral genomes?
Antigenic shift and antigenic drift.
p.11
Viral Reproductive Cycles
What happens after the prophage exits the host bacterial chromosome?
The lytic cycle begins, resulting in the replication, assembly, and release of new λ phages, leading to the lysis and death of the host bacterium.
p.9
Bacteriophages and Their Mechanisms
What occurs during the burst/rise period after the release of new phages?
A sharp rise in the number of infectious phage particles.
p.6
Challenges to the Cell Theory by Viruses
Why can't viruses reproduce on their own?
They lack the machinery to synthesize nucleic acids or proteins.
p.24
Variation in Viral Genomes: Antigenic Drift and Shift
What challenges do antigenic drift and shift pose for influenza?
They result in different subtypes, making effective vaccination and antibody development difficult.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
Why do viral enzymes have high error rates?
Due to the lack of proof-reading function.
p.8
Structure and Components of Viruses
What is a capsid head in bacteriophages?
A structure that contains the capsid coat made up of capsomeres and linear double-stranded DNA.
p.6
Challenges to the Cell Theory by Viruses
How do viruses reproduce within host cells?
By directing the host cell machinery to synthesize viral components.
p.19
Variation in Viral Genomes: Antigenic Drift and Shift
What is antigenic shift in influenza viruses?
It results in influenza viruses with new combinations of glycoproteins.
p.11
Viral Reproductive Cycles
What happens to the viral DNA within the host bacterium during the lysogenic cycle?
The linear viral DNA molecule circularises and integrates into a specific site on the host bacterial chromosome.
p.8
Structure and Components of Viruses
What is the approximate size of the T4 phage?
Approximately 200 nm long and 80-100 nm wide.
p.23
Viral Reproductive Cycles
What is one consequence of the release of matured viruses from host cells?
It may result in cell death due to extensive loss of the cell surface membrane.
p.6
Challenges to the Cell Theory by Viruses
What allows viruses to undergo evolution?
They contain genes and can undergo spontaneous mutation.
p.11
Viral Reproductive Cycles
How does the prophage replicate during bacterial division?
It replicates along with the host's DNA and is passed to daughter bacteria.
p.25
Human Immunodeficiency Virus (HIV) Overview
What triggers the formation of syncytia during HIV infection?
The insertion of newly-synthesized gp120 into the host cell surface membrane, leading to fusion with neighboring T-helper cells.
p.4
Structure and Components of Viruses
What additional components may be found in the viral genome?
Viral enzymes and proteins that stabilize the genome.
p.16
Human Immunodeficiency Virus (HIV) Overview
What happens to the RNA of HIV once it infects a cell?
It is used as a template to make double-stranded DNA.
p.25
Human Immunodeficiency Virus (HIV) Overview
What is syncytium in the context of HIV infection?
Giant multinucleated cells formed by the fusion of adjacent T-helper cells due to HIV infection.
p.23
Viral Diseases and Their Impact on Host Cells
What is the impact of impaired cellular functions on host tissues?
It results in disruption of host tissues and functions, leading to diseases.
