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