Viruses

Are viruses living organisms?

No

What are viruses in retrospect?

Clump of genetic material

How long is a virus roughly?

10-100s of nm

How do viruses “make their living?”

By using a host cell to insert genetic material

What does a virus’s DNA contain instructions for?

To create virons

What are virons?

Particles that contain the genetic material

What is the protein covering on virons called?

Capsid

What is the lipid layer that can also cover virons?

Viral envelope

What are capsids made of?

capsomers

What are capsomers made of?

protomers

What are the viruses that specifically attack bacteria called?

Bacteriophage

What do helical capsid chapes look like?

Rod shaped or filamentous

What do polyhedral capsids look like?

convex icosahedron (20 sided 3D shape)

What is the capsid shape of a bacteriophage?

Prolate

Why do some viruses look spherical but aren’t?

Virons appear spherical due to viral envelope

What are the two infections that cause viruses?

Lytic & Lysogenic

What is the system that puts viruses into different classifications based on DNA/ RNA

Baltimore Classification

Double-stranded DNA viruses are:

Class 1

Single-stranded DNA viruses are:

Class 2

Double-stranded RNA viruses are:

Class 3

Positive-sense single-stranded RNA viruses are:

Class 4

Negative-sense single-stranded RNA viruses are:

Class 5

RNA retroviruses are:

Class 6

DNA retroviruses are:

Class 7

What happens in a Lytic infection?

Virus injects its genome into host cell which cannot tell the difference between its genetic material and the viruses, cell makes mRNA out of virus DNA which makes viral proteins that destroy host cell’s DNA. Virus uses cell to replicate after it dies until it bursts (lyse) from overpopulation of new viruses.

What happens in a Lysogenic infection?

Virus integrates its DNA into host cell’s DNA (virus is called a prophage), prophage stays dormant until generations later in daughter cells, until it leaves the cell’s DNA which directs instruction for new viral proteins.

What are satellite viruses?

Viruses that cannot complete infection process on its own and needs help from other cells/ other viruses.

Are satellite genomes or regular virus genomes shorter?

Satellite

What are satellite nucleic acids?

Satellite viruses that cannot make capsids on their own.

What are virophages?

Subviruses similar to satellites that need help infecting from another virus.

What is the big difference between satellites and virophages?

Virophages remain in host cell’s cytoplasm and hijack cytoplasmic virus factories that are made by the helping virus. (hence the name)

What is the relationship between the virophages and their co-infecting virus?

Parasitic

What are nucleocytoplasmic large DNA viruses?

Viruses that are very large and can infect both the cytoplasm & nucleus of host cell.

What is special about nucleocytoplasmic large DNA viruses?

Its DNA encodes for enzymes involved in DNA replication, repair, and translation.

What are usually the co-infecting viruses that help virophages?

Nucleocytoplasmic large DNA viruses

What are virusoids?

A type of satellite: viroids that have been enclosed in capsid of another virus.

How do virusoids survive?

By relying on the helper virus and host cell’s RNA polymerase 2 for replication.

What genome structure do virusoids have?

Circular, single stranded RNA