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Biology 002 > Virus, Viroid, Prion > Flashcards

Virus, Viroid, Prion Flashcards

Chapter 1

1
Q

What is the role of early viral proteins?

A

Enzymes and regulatory molecules for genome replication.

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2
Q

What are viruses made of?

A

A strand of genetic material (DNA or RNA) within a protective protein coat called a capsid.

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3
Q

Why are viruses considered nonliving?

A

They cannot replicate or survive independently without a host.

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4
Q

What are capsomeres?

A

Structural units that form the capsid of a virus.

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5
Q

What types of symmetry can viral capsids have?

A

Helical, icosahedral, or complex.

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6
Q

How do viruses replicate?

A

By infecting a host cell and using its machinery to produce new virions.

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7
Q

What are the five stages of viral replication?

A

Recognition and attachment, penetration, uncoating, genome replication, and assembly of new particles.

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8
Q

Recognition and Attachment

A

The virus recognizes and binds to specific receptor molecules on the surface of a susceptible host cell

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9
Q

Example of recognition and attachment

A

HIV binds to CD4 receptors on T-helper cells

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10
Q

Penetration

A

The virus enters the host cell through one of the following mechanisms
Direct fusion
Endocytosis
Injection

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11
Q

Penetration: Injection

A

The viral envelope fuses with the host membrane, releasing the viral genome into the cytoplasm. (e.g., HIV)

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12
Q

Penetration: Endocytosis

A

The host cell engulfs the virus into a vesicle, which then releases the viral genome into the cytoplasm. (e.g., influenza virus)

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13
Q

Penetration: Injection

A

The virus injects its genetic material directly into the host cell, leaving the capsid outside. (e.g., bacteriophages)

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14
Q

Uncoating

A

Cell enzymes from lysosomes enter the cell cytoplasm, removing the virus protein coat and making the viral genome accessible for the next stage.

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15
Q

DNA viruses

A

Typically replicate in the nucleus using host DNA polymerase. (e.g., herpesviruses)

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16
Q

Replication (Biosynthesis)

A

The virus hijacks the host cell’s machinery to synthesize viral components.

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17
Q

Replication (Biosynthesis): DNA Viruses

A

Typically, it replicates in the nucleus using host DNA polymerase. (e.g., herpesviruses)

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18
Q

Replication (Biosynthesis): RNA viruses

A

Usually replicate in the cytoplasm using viral RNA-dependent RNA polymerase. (e.g., coronaviruses)

19
Q

Assembly (Maturation)

A

Once sufficient viral components are synthesized, Viral genomes are packaged into newly synthesized capsids and structural proteins are arranged accordingly.

20
Q

. Release

A

Involves the exit of newly formed virions from the host cell:
Lytic viruses
Budding viruses

21
Q

Release: Lytic viruses

A

Cause cell lysis, breaking the host cell open and releasing virions. (e.g., bacteriophages, poliovirus)

22
Q

Release: Budding viruses

A

Exit without immediately killing the host, taking part of the host membrane as an envelope. (e.g., influenza, HIV)

23
Q

What is reverse transcription?

A

A process where retroviruses use reverse transcriptase to convert RNA into DNA.

24
Q

What are helical viruses?

A

Viruses with capsids arranged in a spiral, forming a rod-like structure.

25
Q

What are icosahedral viruses?

A

Viruses with a 20-sided capsid structure.

26
Q

What are complex viruses?

A

Viruses with capsids that are neither helical nor icosahedral, often with additional structures like tails.

27
Q

What are phages?

A

Viruses that infect bacteria.

28
Q

What are enveloped viruses?

A

Viruses surrounded by a lipid bilayer derived from the host cell.

29
Q

Why are enveloped viruses vulnerable to detergents?

A

Detergents disrupt the lipid envelope, inactivating the virus.

30
Q

What are viroids?

A

A plant pathogen the comprise only of ssRNA, with no protein coat

31
Q

Prions

A

A self-replicating particle that is responsible for a range of neurodegenerative disorders in humans e.g. Creutzfeldt-Jakob disease.

32
Q

How do Prions replicate

A

Prions may be altered versions of normal animal proteins, and somehow have the ability to cause the normal version to refold itself into the mutant

33
Q

What are pseudovirions?

A

Host-cell DNA fragments encapsulated in a viral capsid, unable to replicate.

34
Q

What are defective viruses?

A

Viruses with a defective nucleic acid require a helper virus to replicate.

35
Q

Does the DNA of the virus integrate into the host DNA in the lytic cycle

A

No, the DNA of the virus doesn’t integrate into the host DNA in the lytic cycle.

36
Q

Does the DNA of the virus integrate into the host DNA in the lysogenic cycle?

A

Yes, the DNA of the virus integrates into the host DNA in the lysogenic cycle.

37
Q

What happens to the host DNA in the lytic cycle?

A

he host DNA is hydrolyzed (broken down) in the lytic cycle.

38
Q

hat happens to the host DNA in the lysogenic cycle?

A

: The host DNA is not hydrolyzed in the lysogenic cycle.

39
Q

Is there a prophage stage in the lytic cycle?

A

No, there is an absence of a prophage stage in the lytic cycle.

40
Q

Is there a prophage stage in the lysogenic cycle?

A

Yes, the lysogenic cycle includes a prophage stage where viral DNA integrates with the host DNA.

41
Q

How does viral DNA replication occur in the lytic cycle?

A

In the lytic cycle, DNA replication of the virus takes place independently of the host DNA replication.

42
Q

How does viral DNA replication occur in the lysogenic cycle?

A

In the lysogenic cycle, DNA replication of the virus takes place along with the host DNA replication.

43
Q

Are symptoms of viral replication evident in the lytic cycle?

A

Yes, symptoms of viral replication are evident in the lytic cycle.

44
Q

Are symptoms of viral replication evident in the lysogenic cycle?

A

No, symptoms of viral replication are not evident in the lysogenic cycle.

Biology 002 (18 decks)

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