Unit 2 Flashcards
(56 cards)
What can viruses infect?
Animals, bacteria, and plants
Virus structure is composed of _________, __________, and/or __________ depending upon the type of virus.
Envelope, capsid, and genome (DNA or RNA)
Are viruses living?
No;
They need a host to infect
What are the stages of the Virulent phages Lytic Cycle?
- Attachment
- Entry
- Biosynthesis
- Assembly
- Maturation/Release (lysis)
In which stage is the viral DNA introduced into the cell in the Lytic Cycle?
Entry
In which stage of the Lytic Cycle does formation of mature viruses occur?
Assembly
The host DNA is usually degraded during which stage in the Lytic Cycle?
Biosynthesis
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
The virus would not be able to infect new hosts
What are the two types of life cycles that Temperate bacteriophages carry out?
The lytic cycle & the lysogenic cycle
What are the stages of the Temperate bacteriophages Lytic Cycle?
- Attachment
- Entry/Uncoating
- Biosynthesis
- Assembly
- Maturation/Release
What does the bacteriophages DNA form after penetration?
Lytic: circle
Lysogenic: circle; prophage
What are the two things the bacteriophages DNA can do after it becomes a circle?
Continue the lytic cycle or go on to the lysogenic cycle
What are the steps of the lysogenic cycle?
- Attachment
- Entry/Uncoating
- Synthesis
- Assembly
- Maturation/Release
(After Biosynthesis from lytic cycle)
1. Recombination: the phage DNA integrates within the bacterial chromosome
2. Induction: the prophage is excised from the host chromosome
3. Re-enters the lytic cycle
Lysogenic viral DNA which has integrated into the host genome is referred to as?
A prophage
(When the bacterium reproduces the prophage is also copied)
How can induction occur in the lysogenic cycle?
Spontaneously through recombination, some other genetic event, through UV light, or certain chemicals
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
The host cell dies during the lytic stage
What is the fate of the prophage during the lysogenic stage?
It is copied every time the host DNA replicates
Contact between a phage and its bacterial host occurs by _____
A random collision;
As phages are incapable of movement
What portion of bacteriophage T4 enters E. coli?
Only the T4 genome enters the bacterial cell;
The capsid remains on the surface of the cell
Once entry/uncoating into the bacterial cell has been achieved, the next step in a lytic replication cycle is _____
Synthesis
During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules?
Phage enzymes degrade the bacterial DNA
In a lytic cycle of replication, release of phages involves _____
The bacterial cell bursting open;
The bacterial cell undergoes lysis, meaning that it is destroyed. Phages are then released
A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____
The phage genome inserts itself into the host genome (prophage)
What factor may induce a prophage to enter the lytic cycle?
UV Light
