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19 Cards in this Set

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List several unique characteristics of viruses.
1. They are energy less.
2. They are basic life forms that have a protein coat called a capsid.
3. Their genetic material is either DNA or RNA, never both.
Their nucleic acid strands can be single stranded, double stranded, linear or looped in separate segments or one continuous strand. TRUE/FALSE
TRUE.
Regarding RNA viruses, there are 3 types of RNA. What are they?
1. RNA positive stranded
2. RNA negative ''
3. RNA retroviruses.
What is positive stranded RNA?
This means that the RNA is just like a messenger RNA(mRNA). When a positive(+) stranded RNA virus enters a host cell,its RNA can immediately be translated by the hosts ribosomes into protein.
What is negative stranded RNA?
When negative stranded RNA viruses enter a cell, they are not able to begin translation right away.They must first be transcribed into a positive(+) strand of RNA(like mRNA). These must carry in their capsid, an enzyme called RNA dependent RNA polymerase.
Human cells do not have an RNA dependent RNA polymerase, so negative stranded(-) viruses must carry their own.
The RNA of the retroviruses is transcribed in a reverse fashion(retrograde) into DNA. To do this, these viruses carry a unique enzyme called reverse transcriptase. TRUE/FALSE
TRUE.
Every DNA virus has both a negative and positive strand. TRUE/FALSE
TRUE. Unlike + stranded RNA, which is translated directly into proteins, the positive stranded DNA is used as a template for transcription into mRNA.
What are the 2 types of capsids?
1. Icosahedral
2. Helical
What is a capsomer?
If you take 1 or more polypeptide chains and organize them into a globular protein subunit, this will be the building block of our structure.
What is the shape of the capsid?
If you arrange the capsomers into an equilateral triangle, and then place 20 triangles together to form an icosahedron. The DNA or RNA is packaged inside the icosahedral capsid.
What is a helical symmetry capsid?
Here, the `protein capsomers are bound to RNA(always RNA, because only RNA viruses have helical symmetry) and coiled into a helico nucleoprotein capsid.
Most assume a spherical shape except for rhabdoviruses which are bullet shaped.
What is the envelope?
Viruses acquire this membrane by budding through the host cell nuclear or cytoplasmic membrane and tearing off a piece of the membrane as they leave.
Those without an envelope are termed "naked".
Name 4 characteristics regarding how viruses are classified?
1. Nucleic acid
2. Capsid
3. Envelope
4. Size
List 6 DNA viruses and their app. sizes.
1. Parvoviridae(22nm)
2. Hepadnaviridae(42nm)
3. Papovaviridae(50nm)
4. Adenoviridae(80nm)
5. Herpesviridae(150nm)
6. Poxviridae(250nm)
List 9 RNA viruses and their app. sizes.
1. Picornaviridae(27nm)
2. Caliciviridae(30nm)
3. Reoviridae(60nm)
4. Togaviridae(70nm)
5. Coronaviridae(120nm)
6. Orthomyxoviridae(100nm)
7. Rhabdoviridae(70X170nm)
8. Paramyxoviridae(150nm)
9. Retroviridae(120nm)
Most DNA viruses are double stranded, show icosahedral symmetry, and replicate in the nucleus. TRUE/FALSE
TRUE.
List three DNA viruses that are enveloped, and three that are naked.
Enveloped viruses;
Herpes/Hepadna/Pox

Naked;
Papova/Adeno/Parvo
Most RNA viruses are single stranded(half are positive, and half are negative), enveloped, show helical capsid symmetry, and replicate in the cytoplasm. TRUE/FALSE
TRUE.
What are the 6 steps of viral replication?
1. Adsorption
2. Penetration
3. Uncoating
4. Synthesis
5. Assembly
6. Release