Chapter 19 - Viruses Flashcards
Viruses are known as….
Obligate intracellular parasite
What does a virus’s genome consist of?
DNA or RNA not both, single or double stranded
All viruses have ___________ and ___________
And some have __________ and ___________
Genetic material, a protein code
Some have an envelope, spikes (glycoprotein)
Neucloapsid
- Virus genome = nucleic acid core
- capsid (made up of capsomeres)
Viruses can be enveloped or ___________
Naked
What determines the shape of a virus?
Capsid and or envelope determine shape
Some viruses have membraneous envelopes that help them affect hosts along with _______
This is done by a ___________ mechanism
Spikes
“Lock and key”
Viral envelopes surround the ___________ of influenza viruses and many other viruses found in animals
Envelopes are derived from the host cells membrane, contains a combination of viral and host cell molecules
Capsids
What are viruses called that infects bacteria?
They have the most complex capsids found among viruses
The host cell must have a receptor for this virus to attach
Bacteriophages
Each virus has a ___________, a limited number of host cells it can infect
Host range
Viral specificity determines….
Viruses bind/recognize host receptor molecules
Example, HIV targets human T-helper cells
Host range
- phages are the best understood of all viruses
- they just have what two reproductive mechanisms?
The lytic cycle and the lysogenic cycle
What are the steps of viral a replication cycle? ***
- The virus enters the cell and is uncoated, releasing viral DNA and capsid proteins
- Host enzymes replicate the viral genome
- Meanwhile, host enzymes transcribe the viral genome into viral mRNA, which host ribosomes use to make more capsid proteins
- Viral genomes and capsid proteins self assemble into new virus particles, which exit the cell
What kind of viruses can do the lytic cycle or the lysogenic cycle?
Temperate virus
A phage replicative cycle that accumulates in the death of the host cell
Produces new phages and lyses the host cell wall, releasing progeny viruses
The lytic cycle of phage T4
A phage that reproduces only by the lytic cycle is called a….
Virulent phage
Bacteria have defenses against phages, including ____________ that recognize and cut up certain phage DNA
Restriction enzymes
When the viral DNA molecule is incorporated into the host cells chromosomes
Replicates the phage genome without destroying the host
Every time the host divides, it copies the phage DNA and passes the copies to daughter cells
The lysogenic cycle
The integrated viral DNA that happens in the lysogenic cycle is called?
Prophage (viral plus bacterial DNA)
And environmental signal can trigger the virus genome to exit the bacterial chromosome and switch to the ______ mode
Lytic
Phages that use both the lytic and lysogenic cycle‘s are called….
Temperate phages
What are the two key variables used to classify viruses that infect animals?
- DNA or RNA
- single-stranded or double stranded
Many viruses that infect animals have a…
The phospholipid bilayer can fuse with the host
Viral glycoproteins on the envelope bind to specific receptor molecules on the surface of a host cell
Membraneous envelope
Some viral envelopes are formed from the host cells plasma membrane as a viral capsids exits
Other viral membranes form from the house nuclear envelope that are then replaced by an envelope made from…
Golgi apparatus membrane
The broadest variety of RNA genome’s is found in viruses that infect….
Animals
What are viruses called when they use reverse transcriptase to copy their RNA genome into DNA
Retroviruses
HIV is the retro virus that causes AIDS
HIV is considered both a __________ and a ___________
Provirus, retrovirus
