General Biology II Exam 2 - Viruses

just the virus section

What is a virus?

• an obligate intracellular parasite that requires a host cell to reproduce and reproduces at the expense of the host cell

• made of genetic material (DNA or RNA) surrounded by a protein coat called a capsid

• cannot reproduce on its own

• has no metabolism and cannot produce ATP or synthesize its own proteins

• exists outside the host cell as an inactive particle called a virion

What is a capsid?

• the protein coat that surrounds and protects a virus’s genetic material (DNA or RNA)

What is a virion?

• a complete, nonliving virus particle outside a host cell containing genetic material (DNA or RNA) surrounded by protein capsid and may have an outer envelope

What is a retrovirus?

• an RNA virus that uses enzymes reverse transcriptase to convert its RNA into DNA which can integrate into the host cell’s DNA

• retrovirus = RNA -> DNA using reverse transcriptase

What is reverse transcriptase?

• an enzyme that converts viral RNA into DNA, used by retroviruses like HIV. It allows viral DNA to integrate into the host cell’s DNA and helps the virus use the host cells machinery to make more viruses

How do retroviruses convert RNA into DNA?

1. attachment

   1. the virus attaches to a cell

2. entry

   1. the virus enters the cell and releases its RNA

3. reverse transcription

   1. reverse transcriptase converts viral RNA into DNA

4. integration

   1. viral DNA integrates into the host cell’s DNA

5. replication

   1. the host cell’s machinery produces viral RNA and proteins

6. assembly and release

   1. new viruses are assembled and released to infect other cells

• ex: HIV

What is step 1 for retroviruses converting RNA into DNA?

Attachment - the virus attaches to the cell

What is step 2 for retroviruses converting RNA into DNA?

entry - the virus enters the cell and releases its RNA

What is step 3 for retroviruses converting RNA into DNA?

reverse transcription - reverse transcriptase converts viral RNA into DNA

What is step 4 for retroviruses converting RNA into DNA?

integration - viral DNA integrates into the host cell’s DNA

What is step 5 for retroviruses converting RNA into DNA?

replication - the host cell’s machinery produces viral RNA and proteins

What is step 6 for retroviruses converting RNA into DNA?

assembly and release - new viruses are assembled and released to infect other cells

Why are retroviruses problematic?

• they integrate their genetic material into the host cell’s DNA, making them difficult to eliminate

• viral DNA can remain integrated in the host genome

• they damage the immune system

• cause long-term infections as they can persist in the body for years

• they can mutate and evolve, changing genetically, making them harder for the immune system to recognize

How do we characterize viruses?

by their genetic material, structure, shape, size, host specificity, replication, and evolution

How do we characterize viruses by their genetic material?

• DNA or RNA

• single-stranded (SS) or double-stranded (DS)

• positive-sense, negative sense, or ambisense RNA

How do we characterize viruses by their structure?

• a nucleic acid core surrounded by protein coat called a capsid. viruses can be enveloped or nonenveloped

How do we characterize viruses by their shape?

• rods, polyhedrons, spheres, or bacteriophage shapes

How do we characterize viruses by their host specificity?

• host range: types of organisms a virus can infect

• tissue tropism: types of cells a virus can infect

How do we characterize viruses by their replication?

• can reproduce only inside host cells

How do we characterize viruses by their evolution?

viruses can evolve over time

What is the lytic cycle?

• a viral replication cycle in which the virus infects a host cell, makes new viruses, and destroys the host cell when the viruses are released

What is the lysogenic cycle?

a viral replication cycle in which the viral genome integrates into the host cell’s DNA and replicates along with the host DNA, usually without killing the host call

What are the differences between the lytic cycle and the lysogenic cycle?

Lytic cycle:

• destroys the host cell

• makes new viruses immediately

• ends with release of new viruses

• virus is called virulent

Lysogenic cycle:

• usually does not kill the host

• viral DNA integrates into host DNA

• viral genome replicates with host DNA

• virus is called temperate

What is a virulent virus?

• a virus that causes infection by following the lytic cycle, destroying the host cell as new viruses are produced

What is a temperate virus?

• a virus that can enter the lysogenic cycle, integrating its genetic material into the host cell’s DNA without immediately killing the host; can also switch to the lytic cycle under certain conditions

What are some of the neat things that we can exploit about viruses?

biotechnology, medicine, evolution, and disease treatment

How can we exploit viruses in biotechnology?

viral molecules and enzymes, such as reverse transcriptase and restriction enzymes, are useful in biological research

How can we exploit viruses in medicine?

viruses can be used in viral therapy and potentially to help treat diseases, including cancer

How can we exploit viruses in evolution?

viruses contribute to major evolutionary innovations through lateral gene transfer and transduction, which allow genetic material to move between organisms

How can we exploit viruses in disease treatment?

viruses have potential applications in controlling harmful organisms and developing treatments for certain diseases

What is viral therapy?

• the use of viruses to help treat diseases or medical conditions

• examples:

  • cancer treatment

  • gene therapy

  • bacterial infections

What is lateral gene transfer?

• the movement of genetic material between organisms, rather than passing genes from parent to offspring

  • viruses can help transfer genetic material between organisms

  • this can introduce new genes and contribute to evolution

What is transduction?

• a specific type of lateral gene transfer in which a bacteriophage transfers genetic material from one bacteria to another

T/F A virus can reproduce on its own?

False

T/F A virus cannot reproduce on its own?

True

T/F A virus has no metabolism

True

T/F A virus cannot produce ATP or synthesize its own proteins

True

T/F A virus has a metabolism

False

T/F A virus can produce its own ATP and synthesize its own proteins

False

A virus is made of genetic material (DNA or RNA) surrounded by a protein coat called a ____?

capsid

A virus exists outside the host cell as an inactive particle called a _____?

virion

T/F A capsid is a protein coat that surrounds and protects a virus’s genetic material (DNA or RNA)

True

T/F A virion is a protein coat that surrounds and protects a virus’s genetic material (DNA or RNA)

False; capsid

T/F A virus that exists outside the host cell as an inactive particle called a capsid

False; virion

T/F A virus that exists outside the host cell as an inactive particle called a virion

True

A retrovirus is an RNA virus that uses enzymes _________ to convert its RNA into DNA which can integrate into the host cell’s DNA

reverse transcriptase

What’s an example of a retrovirus?

HIV

Which cycle am I describing?
a viral replication cycle in which the virus infects a host cell, makes new viruses, and destroys the host cell when the viruses are released

• destroys the host cell

• makes new viruses immediately

• ends with release of new viruses

• virus is called virulent

Lytic cycle

Which cycle am I describing?
a viral replication cycle in which the viral genome integrates into the host cell’s DNA and replicates along with the host DNA, usually without killing the host call

• usually does not kill the host

• viral DNA integrates into host DNA

• viral genome replicates with host DNA

• virus is called temperate

Lysogenic cycle

T/F The Lytic cycle is a viral replication cycle in which the virus infects a host cell, makes new viruses, and destroys the host cell when the viruses are released

True

T/F The Lytic cycle is a viral replication cycle in which the viral genome integrates into the host cell’s DNA and replicates along with the host DNA, usually without killing the host call

False; Lysogenic

T/F The Lysogenic cycle is a viral replication cycle in which the virus infects a host cell, makes new viruses, and destroys the host cell when the viruses are released

False; Lytic

T/F The Lysogenic cycle is a viral replication cycle in which the viral genome integrates into the host cell’s DNA and replicates along with the host DNA, usually without killing the host call

True

Which cycle releases virulent viruses?

Lytic

Which cycle releases temperate viruses?

Lysogenic

T/F The Lysogenic cycle releases temperate viruses

True

T/F The Lysogenic cycle releases virulent viruses

False

T/F The Lytic cycle releases virulent viruses

True

T/F The Lytic cycle releases temperate viruses

False

T/F A virulent virus is a virus that causes infection by following the lytic cycle, destroying the host cell as new viruses are produced

True

T/F A temperate virus is a virus that causes infection by following the lytic cycle, destroying the host cell as new viruses are produced

False

T/F A virulent virus is a virus that can enter the lysogenic cycle, integrating its genetic material into the host cell’s DNA without immediately killing the host; can also switch to the lytic cycle under certain conditions

false

T/F A temperate virus is a virus that can enter the lysogenic cycle, integrating its genetic material into the host cell’s DNA without immediately killing the host; can also switch to the lytic cycle under certain conditions

true

What are some examples of viral therapy?

• cancer treatment

• gene therapy

• bacterial infections

T/F Viral therapy is the use of viruses to help treat diseases or medical conditions

True

T/F Transduction is the use of viruses to help treat diseases or medical conditions

False; Viral therapy

T/F Viral therapy is a specific type of lateral gene transfer in which a bacteriophage transfers genetic material from one bacteria to another

False; transduction

T/F Transduction is a specific type of lateral gene transfer in which a bacteriophage transfers genetic material from one bacteria to another

true