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Flashcards in Chap8 Deck (14)
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1
Q

Virus

A

Family: viridae. Genus:virus. Specific name: English. Classification based on characteristics: type of host, disease caused, life cycle, naked/enveloped, nucleic acid and strandedness(only in RNAvirus) (+strand=same as mRNA), genome (ss,ds:rna,dna). RNA genomes: + configuration same strand than mRNA (can be translated directly), minus configuration complementary to mRNA (needs to be transcribed into + strand before translated).

2
Q

Life cycle of viruses

A

Adsorption: attachment of virus to specific receptors on surface of host cell. (plant viruses come from insect and mecanical(tear in plants)).
Penetration:Virus genome enters cell. All the virion may enter, or just nucleocapsid (envelopped stays at surface) or just RNA/DNA (capsid left at surface).
Uncoating: removal of enveloppe/capsid by host enzymes (lysosomes).
Replication: of nucleid acid, transcription and protein synthesis.
Maturation: assembly of virus components, nucleic acid, nucleocapsid and proteins to form new virions, all spontaneous.
Release: Mature virions exit host cell by budding or lysis or vectors (plant viruses)

3
Q

Virus replication

A

Latent period: eclipse (enzymes, nucleid acid and proteins are synthesized)+ maturation (assembly). Release: rise period: virions are detected outside the cell, lysis for naked and budding for envelopped virus.Burst size: number of virions released.

4
Q

Bacteriophage

A

Best-studied: E.coli

Most phages contain linear dsDNA genomes. Most are naked, some lipid envelopped.

5
Q

Types of bacteriophage

A
Virulent phages: infection of host cells always leads to replication resulting in cell lysis(lytic pathway). Ex: T4= attaches to LPS by tail fibers which pierce outer membrane and digest peptidoglycan(creating hole).
Temperate phages (2options): lytic pathway. lysogenic pathway: genome becomes incorporated into host genome. Causes latent prolonged state of infection, carried on chromosome (region of viral genome called prophage). ex:lambda(ester lederberg 1950) = linear dsDNA with att region and cohesive ends ssDNA that come together to form circular DNA . Att region is the same as bacteria so it gets into att site of bacteria genome (catalyzed by lambda integrase, a viral enzyme).Lysogen: bacteria contain prophage. Excision:prophage exits chromosome and continues along lytic pathway.
6
Q

ssRNA phage

A

Plus strand DNA phage (same strand as mRNA) but minus strand must be synthesized first to produce a dsDNAgenome, which is the replicative form (ssDNA cannot replicate until it has its complementary strand). Genome is first used as an mRNA and directs the synthesis of an RNAreplicase (RNA dependant RNA polymerase, not performed by host) and other viral proteins. Then, RNA replicase synthesized -strand that is used to produce more +ssRNA (used for mRNA and copies of original genome (+ssRNA)). Ex: MS2.

7
Q

Animals: Location of genome replication

A

In eukaryotic cells, DNA replication occurs in nucleus. It works the same with viralDNA but for viralRNA it’s in the cytoplasm.

8
Q

DNA genome animals

A

Herpes, Papovavirus (human papillomavirus). During penetration, fusion happens and nucleocapsid is transported to nucleus where viralDNA is uncoated. Host synthesized immediates early proteins(TF, virus RNA polymerase), delayed early proteins (virus DNA polymerase, proteins), late proteins (nucleocapsid). Assembly occurs in nucleus, enveloppe via budding through inner membrane, secreted by golgi pathway. If ssDNA, first converted to dsDNA.

9
Q

RNA genome animals

A
    • strand. Genome translated directly. Ex: Hepatitis A + Poliovirus(synthesis of large polyprotein cleaved into proteins. 99% case no symptoms.)
      2. -strand. RNA transcribed into +strand by RNA dependant RNA polymerase. Ex: rabies, influenza, measles(1963 children infected, by2000 no one, new cases due to lack of vaccination with severe complication pneumonia, intellectual disability, death, longterm complications.
      3. dsRNA. First, +strand RNA synthesized by RNA dependent RNA polymerase using -strand. + strand translated into proteins and used a template to yield -strand for dsRNA genome.ex:rotavirus
      4. Retrovirus. 2 identical copies of genome(+strandRNA), reverse transcriptase(RNAdependent DNA polymerase into DNA), integrase and proteases. The DNA genome goes into nucleus and is integrated into host DNA. LTR: long terminal repeats present on viral DNA that contain promoters and help in integration process. Provirus:Integrated viral DNA but cannot excise. Ex: hiv, cancer rous sarcoma virus.
10
Q

Tumor-producing cancer

A

Some viral infections are implicated in turning a normal cell to a cancer cell (immortality=uncontrolled replication) = transformation. Both DNA and RNA. 4 mecanisms: transduction, insertion of strong promoter, inactivation of tumor repressor gene, expression of viral protein that induces transformation (DNA virus)

11
Q

Virus-Transduction

A

RNA virus. Virus carries oncogenes called v-oncogenes(from virus) that are now on the host =transduction. Activates unwanted pattern like transformation which is usually regulated by protooncogenes .Ex: rous sarcoma

12
Q

Virus= Insert a promoter

A

Virus doesn’t encode oncogene. Insertion of strong promoter of virus next to protooncogene expressed protooncogenes at higher levels wanted and misregulates transformation. Retrovirus

13
Q

Virus- Inactivation of tumor-suppressing gene

A

Virus doesn’t encode an oncogene. Insertion of provirus in a gene involved in regulation of proto oncogene expression = uncontrolled expression on protooncogene = transformation happens:( Retrovirus

14
Q

Virus: Expression of viral protein

A

DNA virus. Integration of viral genome into host genome OR viral genome persists. Virus infected a nonpermissive host in which they cannot complete their infection cycle so cell is infected and undergoes replication but it never completes so the cell doesnt die. Human papilloma virus.