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Exam 2 Chap 19
Viruses
55
Biology
Undergraduate 2
10/18/2009

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Term
Tobacco Mosaic Disease
Definition

Stunts the growth of tobacco plants and gives their leaves a mosaic coloration.

In the late 1800's, researchers hypothosized that a particle smaller than bacterica caused the disease. In 1935, Wendell Stanley confirmed this hypothesis by crystallizing the infectious particle.

Term
Viruses = "?"
Definition
"Poison
Term
Are viruses cells? Why or why not?
Definition
NO! They do not respond to stimuli, do not respire, do not grow, do not move...they do reproduce and evolve though.
Term
How large are viruses?
Definition
Very small -200nm - the size of protein.
Term
Depending on its tpe of nucleic acid, a virus is either call a _____ virus or a _____ virus.
Definition
DNA or RNA
Term
Viral envelopes, which are derived from the host cell's membran, contain _____________________.
Definition
a combination of viral and host cell molecules.
Term
Viruses reproduce only in ______ ________.
Definition
Host Cells
Term
Capsid
Definition
the protein shell that encloses the viral genome.
Term
Capsomeres
Definition
protein subunits that capsids are built from.
Term
Once a viral genome has entered a cell, the cell begins to do what?
Definition
the cell begins to manufacture viral proteins.
Term
What are Bacteriophages?
Definition
Also called phages, they are viruses that infect bacteria.
Term
What has the most complex capsids found among viruses?
Definition
Bacteriophages.
Term
Phages have an enlongated capsid head that encloses their
Definition
DNA
Term
The Lytic Cycle
Definition
-Attachment
-Penetration (injection)
-Biosynthesis (nucleic acid and proteins)
-Assembly and Packaging
-Release (lysis)
Term
The Lysogenic cycle replicates the phage genome without doing what?
Definition
The Lysogenic cycle replicates the phage genome without destroying the host.
Term
What does it mean when it is said that Viruses are obligate intracellular parasites?
Definition
They can only reproduce within a host cell.
Term
In the Lysogenic cycle:
The viral DNA molecule is incorporated into the host cell's chromosome how?
Definition
by genetic recombination.
Term
In the Lysogenic cycle:
the integrated viral DNA is known as what?
Definition
prophage
Term
Each virus has a host range. What is that?
Definition
a limited number of host cells that it can infect.
Term
The Lysogenic Cycle:
Definition
-Attachment
-Penetration
-integration
-Normal Cell Reproduction
Term
In the Lysogenic cycle:
Everytime the host divides, it does what?
Definition
it copies the phage DNA and passes the copies to the daughter cells.
Term
Temperate Phages
Definition
Phages that use both the lytic and the lysogenic cycles.
Term
Lytic Cell definition
Definition
A phage reproductive cycle that culminates in death of the host cell.
Term
Lysogenic Cycle definition
Definition
Replication of the phage genome without destroying the host.
Term
Edward Jenner
Definition
inoculated a healthy, 8 year old boy with cowpox in an attempt to find a vaccine for smallpox. It was a success.
Term
Viruses basically take over the ________ of the cell they infect.
Definition
machinery
Term
Prions
Definition
slow acting, virtually indestructible proteins that cause brain diseases in mammals.
Term
Infection
Definition
Pathogen invades body and multiplies in cells and tissues
Term
pathogen
Definition
any disease causing agent
Term
disease
Definition
when body's defense cannot keep pathogen's activites from disrupting normal functions
Term
epidemic
Definition
disease spreads fast through part of a population for a limited time.
Term
pandemic
Definition
empidemic in severel countries at the same time.

ex. h1n1
Term
Why don't pathogens wipe out everything on earth?
Definition
Any species continually attacked by a phathogen has probably developed defenses.

if a pathogen kills too quickly, it might become extinct.
Term
The viral genome cane be either single or double stranded ______ or _______.
Definition
DNA or RNA
Term
RNA viruses require their own supply of certain enzymes because...
Definition
host cells lack enzymes that can replicate viral genome.
Term
Viruses probably evolved from the ___________________.
Definition
cell which they infect.
Term
Viral envelopes, which are derived from the host cell’s ______, contain a combination of viral and host cell molecules.
Definition
membrane.
Term
What is a viral envelope?
Definition
a membrance that cloaks the capsid that in turn encloses the genome.
Term
During the viral reproductive stage, after the viral nucleic acid molecules and capsomeres are produced, they spontaneously do what?
Definition
self-assemble into new viruses.
Term
On a phage AKA the bacteriophage, what encloses their DNA in it?
Definition
Phages have an elongated capsid head that encloses their DNA in it.
Term
On a bacteriophage or phage, attached to their elongated icosahedral heads is a protein tail piece with fibers. What does the phage use that for?
Definition
It uses it to attach to the bacterium it wants to infect. Once it attaches, it injects the Phage's DNA inside.
Term
[image]
Definition
1. Phage attaches to bacterial cell.
2. phage injects DNA
3. Phage DNA directs host cell to make more phage DNA and protein parts.New phages assemble.
4.Cell lyses and releases
new phages.


LYTIC CYCLE
Term
When integrated into the bacterial chromosome by the Lysogenic Cycle, the viral DNA is known as a ____________.
Definition
Prophage
Term
Every time the host divides in the Lysogenic Cycle, it copies the phage DNA and passes the copies to the _________ __________.
Definition
daughter cells
Term
A viral infection can produce symptoms by a number of different routes. In Viral Diseases in Animals, viruses may damage or kill cells by causing the release of hydrolytic enzymes from ___________.
Definition
lysosomes
Term
Some viruses cause infected cells to produce toxins that lead to ________ __________.
Definition
disease symptoms.
Term
In animal viruses, typically, entire capsid enters cell, not just _____ _________.
Definition
genetic material
Term
So, basically the envelope is what?
Definition
an outer membrane.
Term
A vaccine is what?
Definition
a harmless derivatives (typically) of pathogen that stimulate the immune system to mount defenses against the actual pathogen
Term
Vaccines can prevent certain _____ ________.
Definition
viral illnesses
Term
Some symptoms of viral diseases in plants are what?
Definition
spots on leaves and fruits, stunted growth, and damaged flowers or roots
Term
Viral diseases in plants are often carried by what?
Definition
insects.
Term
Smaller, less complex entities called _______ and _______ also cause disease in plants and animals
Definition
viroids and prions
Term
viroid
Definition
a plant pathogen.
Term
When the prion gets into a cell containing the normal fold of protein, the prion somhow converts the normal protein molecules to ______________.
Definition
misfolded prion versions.
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