Virus, Viroid, Prion

Question 1

What is the role of early viral proteins?

Answer 1

Enzymes and regulatory molecules for genome replication.

Question 2

What are viruses made of?

Answer 2

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

Question 3

Why are viruses considered nonliving?

Answer 3

They cannot replicate or survive independently without a host.

Question 4

What are capsomeres?

Answer 4

Structural units that form the capsid of a virus.

Question 5

What types of symmetry can viral capsids have?

Answer 5

Helical, icosahedral, or complex.

Question 6

How do viruses replicate?

Answer 6

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

Question 7

What are the five stages of viral replication?

Answer 7

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

Question 8

Recognition and Attachment

Answer 8

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

Question 9

Example of recognition and attachment

Answer 9

HIV binds to CD4 receptors on T-helper cells

Question 10

Penetration

Answer 10

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

Question 11

Penetration: Injection

Answer 11

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

Question 12

Penetration: Endocytosis

Answer 12

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

Question 13

Penetration: Injection

Answer 13

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

Question 14

Uncoating

Answer 14

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

Question 15

DNA viruses

Answer 15

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

Question 16

Replication (Biosynthesis)

Answer 16

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

Question 17

Replication (Biosynthesis): DNA Viruses

Answer 17

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

Question 18

Replication (Biosynthesis): RNA viruses

Answer 18

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

Question 19

Assembly (Maturation)

Answer 19

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

Question 20

. Release

Answer 20

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

Question 21

Release: Lytic viruses

Answer 21

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

Question 22

Release: Budding viruses

Answer 22

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

Question 23

What is reverse transcription?

Answer 23

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

Question 24

What are helical viruses?

Answer 24

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

Question 25

What are icosahedral viruses?

Answer 25

Viruses with a 20-sided capsid structure.

Question 26

What are complex viruses?

Answer 26

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

Question 27

What are phages?

Answer 27

Viruses that infect bacteria.

Question 28

What are enveloped viruses?

Answer 28

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

Question 29

Why are enveloped viruses vulnerable to detergents?

Answer 29

Detergents disrupt the lipid envelope, inactivating the virus.

Question 30

What are viroids?

Answer 30

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

Question 31

Prions

Answer 31

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

Question 32

How do Prions replicate

Answer 32

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

Question 33

What are pseudovirions?

Answer 33

Host-cell DNA fragments encapsulated in a viral capsid, unable to replicate. ## Footnote Artififcially constructed virus used for study in a lab, contain a viral envolope that enbales the to simulate infection

Question 34

What are defective viruses?

Answer 34

Viruses with a defective nucleic acid require a helper virus to replicate. ## Footnote Hepatitis D Virus is a defective virus that requires Hepatitis B Virus (HBV) as its helper virus. HDV lacks the envelope proteins needed to form infectious virions. Instead, HDV uses the envelope proteins produced by HBV to form new virus-like particles and facilitate its transmission.

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What happens to the host DNA in the lytic cycle?

Answer 37

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

Question 38

hat happens to the host DNA in the lysogenic cycle?

Answer 38

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

Question 39

Is there a prophage stage in the lytic cycle?

Answer 39

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

Question 40

Is there a prophage stage in the lysogenic cycle?

Answer 40

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

Question 41

How does viral DNA replication occur in the lytic cycle?

Answer 41

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

Question 42

How does viral DNA replication occur in the lysogenic cycle?

Answer 42

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

Question 43

Are symptoms of viral replication evident in the lytic cycle?

Answer 43

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

Question 44

Are symptoms of viral replication evident in the lysogenic cycle?

Answer 44

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

Question 45

What is a prophage stage?

Answer 45

The dormant phase of a virus during where the viral genome is integrates into the host's DNA