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Bio Exam 1 > Viruses > Flashcards

Viruses Flashcards

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Biology 101 flashcards
1
Q

What is the structure of a virus?

A

Nucleic acid encased in a protein coat

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2
Q

Where does a virus replicate?

A

In the host cell only

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3
Q

What are the 4 steps of viral replication in a host cell?

A

Replication of viral genome, transcription, translation, reassembly

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4
Q

What does it mean when a virus is an inert particle?

A

No metabolism, replication, or motility

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5
Q

What is the protein coat of a virus called?

A

Capsid, comprised of subunits called capsomeres and carries enzymes

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6
Q

What is the difference between an enveloped and non-enveloped virus?

A

enveloped viruses have a lipid bilayer, making them less resistant to disinfectants

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7
Q

Where is the matrix protein located?

A

Between the envelope and nucleocapsid

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8
Q

What are the different types of viral genome?

A

DNA or RNA, linear or circular, double or single-stranded

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9
Q

How do viruses attach to the host cell?

A

Protein components, tail fibers in phages, spikes in some animal viruses

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10
Q

What are the 4 different types of viruses?

A

helical, icosahedral, complex, and spherical

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11
Q

What are the 3 types of bacteriophages(viruses that infect bacteria)?

A

Lytic phages, temperate phages, filamentous phages

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12
Q

What is the characteristic of a lytic phage?

A

When they exit the host cell, the cell undergoes lysis(it bursts)

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13
Q

What are the 5 steps of the lytic cycle?

A

attachment, entry of phage dna and degradation of host dna, synthesis of viral genomes/proteins, self-assembly of proteins, release

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14
Q

What is the burst size of a bacterial cell?

A

The amount of phage particles released upon lysis

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15
Q

What are the steps of the lysogenic cycle?

A

integration of phage DNA, cell division, formation of daughter cell with prophage

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16
Q

What are the bacterial defenses against phages?

A

preventing phage attachment, restriction enzymes, crispr/cas

17
Q

How do bacteria prevent phage attachment?

A

Absence of receptors on surface, or alteration of receptors so that phages cannot bind

18
Q

How do restriction enzymes work?

A

They prevent phages from replicating genome inside the bacterial cell by recognizing and cutting short nucleotide sequences into small, non-infectious fragments. Can also occur by methylating host DNA to distinguish from phage DNA

19
Q

How does the CRISPR/Cas system work?

A

Infection by phage triggers expression of CRISPR(clustered regularly interspaced short palindromic repeats), from phages that previously infected the cell. Then the RNA transcript is processed into short strands, and each strand binds to a CAS protein forming a complex. Complementary RNA binds to phage dna, and then CAS cuts the segment. the DNA from the phage is now degraded.

20
Q

What are the key characteristics of animal viruses?

A

DNA or RNA based, single or double stranded, enveloped or non enveloped, hosts are infected

21
Q

What is the central dogma of biology?

A

DNA to RNA to proteins

22
Q

What are some aspects of synthesis of viral genetic material?

A

Expression of viral genes to provide structural and catalytic genes(capsid, replication enzyme)
synthesis of multiple copies of genome

23
Q

What are the three viral replication strategies?

A

DNA viruses, RNA viruses, reverse transcribing viruses

24
Q

What is the difference between sense and antisense strands?

A

the template strand is antisense and noncoding, and the nontemplate strand is sense and coding

25
Q

Why is antisense RNA present in a cell?

A

inhibits translation machinery by base pairing with sense RNA and activating RNAse H to develop novel transgenic

26
Q

How do DNA viruses replicate?

A

ds dna becomes rna and then protein; for ss rna the complement is synthesized and the same thing happens. uses dna and rna-dependent dna polymerase

27
Q

How do RNA viruses replicate?

A

replicate in cytoplasm, require virally encoded RNA polymerase(replicase), which allows genetic drift because it lacks proofreading. ss sense RNA is used as MRNA, anything else is converted by synthesizing complement

28
Q

What is the replicative cycle of an enveloped RNA virus?

A

glycoproteins on viral membrane bind to host cell, capsid and viral genome enter cell and enzymes release the genome, viral rna polymerase synthesizes complement of viral genome, new copies of genome are synthesized, mrna(complementary) is translated into protein, vesicles transport protein to virus and the capsid assembles. then the virus exits with a shit ton of glycoproteins on the membrane.

29
Q

How do new viruses emerge?

A

mutation of existing viruses, spread due to international travel, spread of existing viruses from other animals

30
Q

How do reverse transcribing viruses replicate?

A

encode reverse transcriptase(make DNA from RNA)(retroviruses have ss + rna), then the complementary strand is synthesized and the dsdna is integrated into the host cell’s chromosome.

31
Q

What are the 3 genes all reverse transcribing viruses have?

A

gag(viral protein coat), pol(reverse transcriptase and integration of DNA), env(glycoproteins on viral membrane)

32
Q

What is the replicative cycle of HIV?

A
  1. envelope glycoproteins enable the virus to bind receptors on white blood cells
  2. virus fuses w host cells plasma membrane
  3. capsid is removed, releasing rna, viral proteins, adn reverse transcriptase
    4.rt synthesizes dna
  4. rt catalyzes complementary strand synthesis
  5. dna is integrated into host cell dna
  6. proviral genes are transcribed onto rna
  7. capsid and rt are made in cytosol, envelope glycoproteins made in er
  8. capsid and glycoproteins assemble around the viral molecule
33
Q

What are prions?

A

proteinaceous infectious agents, no nucleic acid
causes slow fatal diseases like mad cow

Bio Exam 1 (7 decks)

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