AP Bio Ch 18
Steps of the Lytic Cycle
1)Phage attaches to receptor site 2)Phage injects tail into bacteria, which releases phage's DNA 3) The capsid is left empty and the DNA is hydrolyzed 4) Phage DNA uses host cell's organelles to make phage proteins to create phage parts, which later on converge 5) The membrane of the host is broken(sometimes of the production of lysosomes by the phage) and the phage successors move on to infect other bacteria cells.
Why do RNA viruses tend to have high rates of mutations?
Because they do not have the proofreading steps of DNA replication
What cycles do phages use to reproduce?
Lytic and lysogenic cycle
Plant viruses normally mostly consist of what type of genome?
Rna
Steps of the lysogenic cycle
Step 1) Phage injects its genome into host cell. 2) the genome converges with the host's genome(now called a prophage) 3) As bacteria reproduces, the phage genome does so along with it. 4) Occasionally a prophage exits the bacterial chromosome, initiating a lytic cycle.
provirus
The newly made DNA converges within the chromosome within the host's cell's nucleus(now called a provirus) Unlike a prophage, a provirus never leaves.
restriction nuclease
a defensive mechanism that some bacteria have; enzyme that cuts up unfamiliar DNA within the host's genome.
virulent phage
a phage that uses the lytic cycle
viral genomes
all vary...some are double stranded/single stranded...DNA/RNA, have four nucleuotides/ thousands of nucleuotides
most RNA viruses infect which hosts?
animal cells
viroids
are prevalent in plants....only consist of a singular ring made up of only several hundred nucleotides long...somehow they can stunt plant growth and metabolism.
lytic cycle
cycle that culminates in the death of the host cell
host range
each type of virus can infect and parasitize only a limited range of host cells. This host specificity depends on the evolution of recognition systems of the viruses.
What causes viruses to switch from lysogenic to lytic?
environmental triggers, such as radiation or the presence of certain chemicals that swithces the virus from the lysogenic to th lytic cycle.
How do retroviruses reproduce?
enzyme reverse transcriptase transribes DNA from a Rna template. The newly made DNA converges within the chromosome within the host's cell's nucleus(now called a provirus)
reverse transcriptase
enzyme that transcribes DNA from a RNA template for retrovirus reproduction
prions
infectious proteins....interestingly unknown how it works because proteins do not replicate themselves. Thus, it probably induces the host cell's existing proteins.
viral envelope
membranes that cloth the capsid of a virus
What is a major source to new viral disease?
mutations and spread of disease within different species
temperate phages
phages that are capable of using both modes of reproducing within a bacterium.
What are capsids made of?
protein called capsomeres
capsid
protein shell that encloses the viral genome. Shapes vary from virus to virus
lysogenic cycle
replicates the phage genome without destroying the host.
prophage
the bacteria/virus, when the host's genome and phage's genome converge
viral envelopes
the virus uses it to enter through the cell's lipid bilayer. Sometimes, it is derived from the host cell itself while the virus leaves the host cell. Thus, it too has the necessary glycoproteins required to attach to the host cell.
How do viroids work?
they use cellular enzymes because they cannot generate any of their own
bacteriophages(aka phages)
viruses that infect bacteria
retrovirus
where they have a RNA genome and the host cell has a DNA genome...HIV is a retrovirus
where is the reproducing site for a virus?
within a host cell
Can viruses cause cancer?
yes