chapter 5 and 11 p2 Flashcards
What is generalized transduction?
It’s a process where bacterial DNA is transferred by a phage to a new host cell.
What happens when a phage infects the donor bacterial cell?
Phage DNA and proteins are made, and the bacterial chromosome is broken into pieces
How does bacterial DNA get packaged into a phage capsid?
Occasionally, pieces of bacterial DNA are mistakenly packaged during phage assembly
What happens when the donor cell lysates?
It releases phage particles containing bacterial DNA.
What happens when a phage carrying bacterial DNA infects a recipient cell
Recombination can occur, producing a recombinant cell with a different genotype.
What happens to the recombinant cell?
It reproduces normally, with a new genotype from both donor and recipient cells.
What happens during the attachment of a virus to the host cell?
The virus attaches to the surface of the host cell.
What happens after the virus injects its DNA into the host cell?
Lytic events are initiated, and the virus begins replication.
What is induction in the context of viral infection?
Induction is the activation of the viral genome from a latent state to initiate lytic events.
What occurs during the synthesis and assembly of phage components?
Viral components are synthesized, and new virions are assembled.
What happens when viral DNA is integrated into the host DNA
The viral DNA becomes part of the host’s genome and replicates with it.
What happens during cell division of a lysogenized cell?
Viral DNA is replicated along with the host DNA at each division.
What happens during lysis of the host cell?
The host cell bursts, releasing new phage virions.
What is a lysogenized cell?
A cell that carries a prophage (integrated viral DNA) in its genome.
What happens when a prophage exists in a galactose-using host?
The prophage exists in a host containing the gal gene, which is responsible for galactose metabolism.
What happens when the phage genome excises from the host?
The phage genome excises, carrying the adjacent gal gene from the host.
What happens when the phage matures and the cell lyses?
The phage matures and the cell lyses, releasing phage carrying the gal gene.
What happens when the phage infects a galactose-negative cell?
The phage, along with the gal gene, integrates into the recipient cell’s DNA.
What happens after the gal gene integrates into the recipient cell’s DNA?
The lysogenic cell can now metabolize galactose, becoming a galactose-positive recombinant.
What type of cell is created after the integration of the gal gene?
A galactose-positive recombinant cell is formed.
What is rolling circle replication in the context of the lambda phage genome?
It is a mechanism where the lambda phage DNA is replicated in a circular form, leading to continuous synthesis of new viral genomes.
What happens in the initial step of rolling circle replication?
The phage genome is nicked at a specific site, allowing the 3’ end to be extended while the 5’ end remains attached.
What happens after the nick in rolling circle replication?
The free 3’ end serves as a primer for continuous DNA synthesis, producing a long single-stranded DNA.
What happens after the new DNA strand is synthesized in rolling circle replication?
The newly synthesized strand is then cleaved into individual genomes, which are packaged into phage heads.
What is the result of rolling circle replication in the lambda phage?
Multiple copies of the lambda genome are produced, ready for packaging into new virions.
What are eukaryotic mechanisms to diminish viral infections?
immune defense mechanisms
RNA interference
What is RNA interference in eukaryotes?
A mechanism that silences viral RNA, preventing viral replication.
What mechanisms do prokaryotes use to diminish viral infections?
CRISPR
Restriction modification system
What is CRISPR in prokaryotes?
A system that stores viral DNA sequences and uses them to target and destroy future viral infections.
How does the restriction modification system work in prokaryotes?
It cuts foreign viral DNA, but viruses can counteract it by modifying their DNA or producing inhibitory proteins.
What happens during the attachment of animal viruses?
Viruses attach to the host cell membrane.
How do animal viruses enter the host cell?
Through endocytosis or fusion.
What occurs during uncoating of the virus?
The viral or host enzymes break down the viral capsid, releasing the genome into the host cell.
What is biosynthesis in the context of animal viruses?
It’s the production of viral nucleic acids and proteins inside the host cell.
What happens during assembly/maturation of the virus?
Viral nucleic acids and capsid proteins assemble into new virions.
How do animal viruses release from the host cell?
Budding (for enveloped viruses)
Rupture (for non-enveloped viruses)
A viral one-step growth curve. what are the parts
initial dip. eclipe period
rise- virions released from host cell
acute infection- plateau before drop
What happens when viral DNA enters the host cell nucleus?
The viral DNA is integrated into the host’s chromosome as a provirus by viral integrase.
What happens when the provirus is replicated?
The provirus is replicated along with the host cell’s DNA
What occurs during the transcription of the provirus?
RNA is produced for new retrovirus genomes and RNA encoding viral proteins (capsid, enzymes, and envelope proteins).
How are viral proteins processed in the retrovirus lifecycle?
Viral proteins are processed by viral protease and some are moved to the host cell’s plasma membrane.
How does the mature retrovirus leave the host cell
the retrovirus buds out, acquiring an envelope and attachment spikes.
What is the role of reverse transcriptase in the retrovirus lifecycle?
Reverse transcriptase converts viral RNA into DNA, which is integrated into the host’s genome.
What viral structures are involved in retrovirus replication?
Viral RNA
Reverse transcriptase
Capsid
Envelope
What is a provirus?
A provirus is viral DNA integrated into the host cell’s chromosome, which can be replicated and transcribed.
What is unique about the genome of retroviruses?
Retroviruses have two identical ssRNA molecules that resemble mRNA.
What does the gag gene in a retrovirus encode?
The gag gene encodes structural proteins for the viral capsid
What does the pol gene in a retrovirus encode
The pol gene is translated into a large protein that contains reverse transcriptase and integrase.
What does the env gene in a retrovirus encode?
the env gene encodes two envelope proteins.
What characterizes latent viral infections?
The virus remains in an asymptomatic host cell for long periods.
What are examples of latent viral infections?
Cold sores (Herpes simplex virus)
Shingles (Varicella-zoster virus)
What characterizes persistent viral infections?
The disease process occurs over a long period and is generally fatal.
What is subacute sclerosing panencephalitis?
It is a rare, fatal disease caused by the measles virus that occurs years after the initial infection.
latent infection-
when on curve it rises again not as much as acute infection then drops again
persistent infection in curve graph
slow increase but never spikes after acute infection
How do activated oncogenes contribute to cancer?
Activated oncogenes transform normal cells into cancerous cells.
What characteristics do transformed cells exhibit?
Increased growth
Loss of contact inhibition
Tumor-specific transplant antigens
T antigens
How do oncogenic viruses contribute to cancer?
The genetic material of oncogenic viruses becomes integrated into the host cell’s DNA.
What are examples of oncogenic DNA viruses?
Adenoviridae
Herpesviridae (e.g., Epstein-Barr virus)
Poxviridae
Papovaviridae (e.g., Human Papillomavirus, Polyomavirus SV40)
Hepadnaviridae
What is an example of an oncogenic RNA virus?
Retroviridae, including HTLV-1 and HTLV-2.
How do oncogenic RNA viruses contribute to cancer?
Viral RNA is transcribed to DNA, which can integrate into the host cell’s DNA.
What type of virus is Parvoviridae?
It is a nonenveloped single-stranded DNA virus.
What disease is associated with Parvoviridae?
Fifth disease
Anemia in immunocompromised patients
What type of virus is Adenoviridae?
It is a nonenveloped double-stranded DNA virus.
What diseases are associated with Adenoviridae?
Respiratory infections in humans
Tumors in animals
What is Papovaviridae?
It is a family of nonenveloped double-stranded DNA viruses, including Papillomavirus and Polyomavirus.
What diseases are caused by Papillomavirus (a member of Papovaviridae)?
Human wart virus
Some strains can cause cancer (e.g., cervical cancer).
What do Polyomavirus viruses cause?
They can cause tumors, and some strains are oncogenic (can cause cancer).
What type of virus is Poxviridae?
Poxviridae are enveloped double-stranded DNA viruses.
What are some examples of Orthopoxvirus (within the Poxviridae family)?
Vaccinia virus
Smallpox virus
What diseases are caused by Poxviridae viruses?
Smallpox
Molluscum contagiosum
Cowpox
What type of virus is Herpesviridae?
Herpesviridae are enveloped double-stranded DNA viruses.
What are some examples of Herpesviridae viruses?
Simplexvirus (HHV-1, HHV-2)
Varicellovirus (HHV-3)
Lymphocryptovirus (HHV-4)
Cytomegalovirus (HHV-5)
Roseolovirus (HHV-6, HHV-7)
Kaposi’s sarcoma virus (HHV-8)
What is a unique feature of Herpesviridae viruses?
Some herpesviruses can remain latent in host cells.
What type of virus is Hepadnaviridae?
Hepadnaviridae are enveloped double-stranded DNA viruses
What is the example of Hepadnaviridae?
Hepatitis B virus.
What is a unique characteristic of Hepadnaviridae?
They use reverse transcriptase during their replication cycle.
