Viruses, Prions, and Viroids Lecture Review

Comprehensive flashcards covering virus classification, reproductive cycles, retroviruses, and infectious particles like prions based on lecture notes.

What is the typical size range of a virus?

$10$ to $250\,nm$ (nanometres)

What are the two components that all viruses possess?

A protein coat called a capsid and genetic material, which is either RNA or DNA.

What is the primary difference between a naked virus and an enveloped virus?

A naked virus consists of only a capsid and nucleic acid, while an enveloped virus has an extra layer made of lipids on the outside of the capsid.

What are bacteriophages, or phages?

Viruses that only invade bacteria or archaea.

What are the two main reproductive cycles used by viruses?

The lytic cycle and the lysogenic cycle.

In which reproductive cycle does the virus's genetic material bind with the host cell's chromosome?

The lysogenic cycle.

What are the six steps of the Lytic Cycle as described in the notes?

1. Attachment, 2. Entry, 3. Uncoating, 4. Replication, 5. Assembly, and 6. Lysis and Release.

How does the entry step of the lytic cycle differ for a bacteriophage compared to other viruses?

A bacteriophage releases enzymes to dissolve the host cell and injects nucleic acid, whereas other viruses merge with the host cell membrane to be brought inside.

What is the role of viral RNA in an RNA virus?

It acts like messenger RNA (mRNA), instructing the host cell to manufacture viral RNA and viral proteins.

Which three examples of RNA viruses are provided in the transcript?

Rabies, influenza, and rubella.

How does a retrovirus create viral DNA?

It injects RNA along with an enzyme into the host cell; the enzyme then helps create viral DNA from the viral RNA.

What is a provirus?

The state of a retrovirus after its viral DNA enters the nucleus and attaches itself to the host cell's DNA.

Why is a body infected with HIV unable to defend itself from other invading microorganisms?

Because the virus attacks white blood cells.

How is influenza primarily spread and what is its incubation period?

It is spread by air-borne particles from coughing and sneezing, with an incubation period of $1$ to $4$ days.

What are prions and what biological material do they lack?

Prions are infectious particles consisting mostly or entirely of a single protein that damage nerve cells; they lack RNA or DNA.

What are two specific diseases caused by prions?

Creutzfeldt-Jacob disease (CJD) in humans and bovine spongiform encephalopathy (BSE) or ‐mad cow disease.‐

How do prions differ from normal proteins in the body?

They have the same chemical composition but a different shape.