Biology II Ch 19

restriction enzymes

bacteria's defense against phages recognize & cut up certain phage DNA

what does viral genome consist of

consists of double or single stranded RNA or DNA

discovery of viruses

adolf mayer & dimitri ivanowksy hypothesized that a particle smaller than bacteria caused TMV wendall stanley confirmed that it was a virus by crystallizing the infectious particle

virus treatment

little can cure it antibiotics for bacteria do not work bc they have few/no enzymes of their own antivirals

phage's 2 reproductive cycles

lytic & lysogenic cycle

vaccines

harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen eradicated small pox

acyclovir

inhibits viral polymerase that synthesize viral DNA for herpes

prophage

integrated viral DNA

provirus

integrated viral DNA unlike prophage, remains permanent resident of the host cell host's RNA polymerase transcribes the proviral DNA into RNA molecules

azidothymidine (AZT)

interferes with reverse transcriptase for AIDs

antivirals

nucleotides that interfere with polymerase that synthesize viral DNA

bacteria

prokaryotes with cells smaller & more organize than eukaryotes

lysogenic cycle

replicates phage genome without destroying host viral DNA is incorporated by genetic recombination into host cell's chromosome every time host divides, it copies the phage DNA & passes copies to daughter cells

viruses

smaller & simpler than bacteria genes packaged into protein coat, sometimes membranous envelope obligate intracellular parasite

If you were a researcher trying to combat HIV infection, what molecular processes could you attempt to block?

medications target reverse transcriptase cannot immunize bc there are many mutations of the virus (mutations caused by reverse transcriptase not being good at its job bc its transcribes RNA to DNA differently each time)

emerging viruses

those that appear suddenly or suddenly come to the attention of scientists (AIDs, west nile virus, SARS)

what do viruses use enzymes, ribosomes, & small host molecules for?

to synthesize progeny viruses

herpes virus

DSDNA reproduce within host cell nucleus copies of virus DNA remain as mini chromosomes in nuclei of certain nerve cells remain latent until physical/emotional stress causes blister flare ups throughout life

If Beijerinck had observed that the infection of each group was weaker than that of the previous group and that ultimately the sap could no longer cause disease, what might he have concluded?

Infection was caused by a toxin since replication did not occur.

A researcher lyses a cell that contains nucleic acid molecules and capsid units of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur? a. The plants would develop some but not all of the symptoms of the TMV infection. b. The plants would develop the typical symptoms of TMV infection. c. The plants would not show any disease symptoms. d. The plants would become infected, but the sap from these plants would be unable to infect other plants.

The plants would develop the typical symptoms of TMV infection. (correct)

obligate intracellular parasite

can produce only within host cell

membranous (viral) envelope

derivative of host cell's membrane surrounds capsid of virus contains combination of viral & host cell molecules many viruses that infect animals have this viral glycoproteins on the envelope bind to specific receptor molecules on the surface of a host cell

cause of emerging viruses

existing viruses that increase their host territory mutation of virus dissemination from a small isolated population spread from other animals

avian flue fears

high kill rate

prokaryotes

no organelles, no nucleus

lytic cycle

phage reproductive cycle culminates in death of host cell produces new phages & digests host's cell wall releasing progeny viruses

virulent phage

phage that reproduces only by lytic cycle

temperate phages

phages that use both lytic & lysogenic cycles

capsid

protein shell that encloses the viral genome built from capsomeres

HIV

retrovirus that causes AIDs

tobacco mosaic disease

stunts growth of tobacco plants gives leaves mosaic coloration caused by filtered sap being rubbed on healthy plants therefore infecting them

retrovirus

use reverse transcriptase to copy their RNA genome into DNA

broadest variety of RNA genomes are found in

viruses that infect animals

bacteriophage

viruses that infect bacteria most complex capsids found among viruses elongated capsid head encloses their DNA protein tailpiece attaches phage to host & injects phage DNA inside