virus and priods Flashcards
a virus that cause specific types of cancer, including
human cancers such as lymphomas, carcinomas, and some types of leukemia
oncoviruses
The viruses that infect bacteria are known as
bacteriophages
three categories of
bacteriophages, based on their shape
- Icosahedron bacteriophages
- Filamentous bacteriophages
- Complex bacteriophages
an almost spherical shape bacteriophages
- Icosahedron bacteriophage
bacteriophages that have a long tube formed by
capsid proteins assembled into a helical structure
Filamentous
always cause what is known as the lytic cycle, which ends with the destruction (lysis)
Virulent bacteriophages
bacteriophages that infect Escherichia coli are called
coliphages
steps in the lytic cycle
attachment
penetration
assembly
biosynthesis
release
(adsorption) of the phage to the surface of the bacterial cell what step of the lytic cycle is this
attachment
In this step, the phage injects its DNA into the bacterial cell, acting much like a hypodermic needle
From this point on, the phage DNA “dictates” what occurs within the bacterial cell. T
penetration
during this step that the phage genes are expressed
the host cell’s enzymes are used to make viral DNA
and viral proteins
biosynthesis
the viral pieces are assembled to produce complete viral particles (virions). It is during this step that viral DNA is packaged up into capsids.
assembly
this is when the host cell bursts open and all of the new virions escape from the cell
release
these bacteriophages do not immediately initiate the lytic cycle, but rather, their DNA remains integrated into the bacterial cell chromosome,
generation after generation
temperate phages (also known as lysogenic phages
Latent viral infections are usually limited by the defense systems of the human body—phagocytes and antiviral
proteins called
interferons
have been developed to interfere with virus-specific enzymes and virus
production by either disrupting critical phases in viral cycles
antiviral agents
Drugs used to treat
viral infections are
called
antiviral agents.
Human Immunodeficiency Virus is a member of a genus of viruses called
lentiviruses
An extremely large double-stranded DNA virus, recovered from amebas it “mimics” bacteria
Mimivirus
are infectious RNA molecules that
cause a variety of plant
diseases
Viroids
are small infectious proteins that apparently cause fatal neurological diseases in animals, such as scrapie
Prions
Of all pathogens, ____ are
believed to be the most resistant to disinfectants.
prions
- Which one of the following steps occurs during the
multiplication of animal viruses, but not during the
multiplication of bacteriophages?
a. assembly
b. biosynthesis
c. penetration
d. uncoating
d
- Which one of the following diseases or groups of
diseases is not caused by prions?
a. certain plant diseases
b. chronic wasting disease of deer and elk
c. Creutzfeldt-Jacob disease of humans
d. “mad cow disease”
a
- Most procaryotic cells reproduce by:
a. binary fission.
b. budding.
c. gamete production.
d. spore formation.
a
- The group of bacteria that lack rigid cell walls and
take on irregular shapes is:
a. chlamydias.
b. mycobacteria.
c. mycoplasmas.
d. rickettsias.
c
- Which one of the following statements about rickettsias is false?
a. Diseases caused by rickettsias are arthropod-borne.
b. Rickets is caused by a Rickettsia species.
c. Rickettsia species cause typhus and typhuslike
diseases.
d. Rickettsias have leaky membranes
b
- Which one of the following statements about
Chlamydia and Chlamydophila spp. is false?
a. They are obligate intracellular pathogens.
b. They are considered to be “energy parasites.”
c. The diseases they cause are all arthropod-borne.
d. They are considered to be Gram-negative bacteria
c
- An organism that does not require oxygen, grows
better in the absence of oxygen, but can survive in
atmospheres containing some molecular oxygen is
known as a(n):
a. aerotolerant anaerobe.
b. capnophile.
c. facultative anaerobe.
d. microaerophile.
a
