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33 Cards in this Set

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The land of the super tiny! From 3-200 genes; Obligate intracellular parasites; Known from ancient times

Viruses

General Characteristics

Not Cells


obligate intracellular parasites


small.. 20nm - 350nm


Single type of nucleic acid


Protective Coat


Specific "Host Range"

Virus Structure


Capsids, Nucleic Acid, Envelope

Icosahedral, Helical

What is a Capsid?

protein coat that surrounds the nucleic acid


protects genome


recognizes/binds host


stimulate immune system


made of viral capsid protein (capsomeres)

What are Capsomeres?

subunits of the protein coat

What is the symmetry of Icosahedral?

12 corners


20 faces


30 edges




VERY STABLE




**NUCLEIC ACID usually not ordered inside

Describe the envelope...

Made of host membrane


recognizes/binds to host


protects capsid



Internal properties

RNA or DNA (not both)


* only viruses among all of life can have RNA as a genome


Single stranded or double stranded


**only viruses among all of life can have single stranded genomes


One piece or multiple


Linear or circular


As few as 3 genes, as many as 250

Structure of an Influenza virus...

Envelope


Spkies


Helical nucleoprotein


has ssRNA in 8 segments

What are bacteriophages?

Viruses of bacteria

Bacteriophage viral multiplication...

RAPI-BAR


Recognition


Attachment


Penetration


Insertion


Biosynthesis


Assembly


Release

Animal viral multiplication...

RAPI-UBAR


Recognition


Attachment


Penetration


Endocytosis or fusion


Stimulated by attachment


Uncoating: capsid unchaste away from nucleic acid


How the DNA/RNA gets out


Biosynthesis


Assembly


Release

Explain Endocytosis..

Virus is "eaten" by cell- uptake in vacuole


Exists in a membrane bound vesicle (from host)


Must be uncoated in separate step


EX: herpes virus



Explain Fusion...

Virus coat blends into the plasma membrane of the host


No vesicle


Is uncoated in the same step as penetration


EX: Mumps virus

DNA viral replication

Inside the cytoplasm- gets moved to the nucleus

DNA viral replication inside the nucleus...

Gets transcribed into mRNA (just like a host DNA)


mRNA gets shipped out with the host mRNA to the ER to be translated by ribosomes


Host machinery makes the viral proteins


Costs the host lots of energy to do

RNA viral replication...

RNA viruses come in different "flavors"


(+) RNA


(-) RNA


dsRNA


Retroviruses

Retroviruses viral replication..

goes against the grain!


Use their sRNA to make sand


---in cytoplasm


---use viral enzyme- reverse transcriptase


sand becomes complemented into sDNA


--in cytoplasm


sDNA then goes to nucleus


--follows DNA viral replication process




EX: HIV comes in single stranded RNA virus

What are Polymerases???

enzymes that "polymerize" either DNA or RNA


--makes more DNA or RNA


--used in REPLICATION and TRANSCRIPTION


--needs a template to work off of

DNA polymerases

DNA to DNA


aka DNAdependent DNA polymerase


Transcriptase (a polymerase): DNA to mRNA


tRNAS, rRNA


DNA viruses


--can use cellular polymerases or can code for their own DNA polymerase and transcriptase.

Retroviruses (also RNA viruses) Polymerases...


Reverse transcriptase....


...."RNA dependent DNA polymerase"


---uses RNA as a template to go backwards and make DNA




** THESE are unique polymerases and are found only with viruses***

(+) RNA viral replication

ready to be transcribed


genes are in correct direction (5'-3')


same polarity as mRNA


Ribosomes in the cytoplasm translate the RNA


Viral proteins are then able to be packaged

(-) RNA viral replication


not ready to be transcribes


genes are going wrong direction ( 3'-5')


(-) RNA strand becomes a "template" to make a (+) RNA strand


---reverse and complemented


Ready to be translated by ribosmoes

Capside Viruses

mature virions in the nucleus or cytoplasm


--many copies ( up to 100,000)


So much energy was uses to make these call death usually occurs ( cell lysis)


** Releases mature virions into the environment

Enveloped viruses...

bud out using the host as a new envelope


EX: HIV


dictate the exit


viruses start pushing on cell membrane and "bleb out"

Types of ACUTE virus infections:


influenza, rotavirus, WNV

types of PERSISTENT virus infections:

HIV, Congenital Rubella

types of RECURRENT viral infections

Herpes simplex (cold sores)

types of LATENT viral infections

Varicella Zoster (chicken pox)


**insert genetic material into one of your chromosomes--time passes and becomes active as shingles.

types of ONCOGENIC viral infections

Human Papilloma Virus (HPV)

Characteristics of Influenza...

(-) RNA virus


contains 11 genes on 8 pieces of RNA


roughly 10,000 bases long


---average bacteria about 4.6 million bases


--human genome about 3.2 billion bases


RNA dependent RNA polymerase makes a mistake once every 10,000 bases


mutations occur all the time (poor repair mechanisms)

Swine flu

H1N1


H--- hemagglutinin


------ 16 subtypes


N----neuraminidase


-----9 subtypes


Is the same HN type as the pandemic of 1918

Swine flu pandemic of 1918

killed 30-100 million people


---came in two waves


infected 500 million


most victims were young, otherwise heathy


---influenza typically kills the very young,old or immunocompromised


aka "spanish flu"