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19 Cards in this Set
- Front
- Back
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List several unique characteristics of viruses.
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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. |
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Their nucleic acid strands can be single stranded, double stranded, linear or looped in separate segments or one continuous strand. TRUE/FALSE
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TRUE.
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Regarding RNA viruses, there are 3 types of RNA. What are they?
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1. RNA positive stranded
2. RNA negative '' 3. RNA retroviruses. |
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What is positive stranded RNA?
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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.
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What is negative stranded RNA?
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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. |
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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
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TRUE.
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Every DNA virus has both a negative and positive strand. TRUE/FALSE
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TRUE. Unlike + stranded RNA, which is translated directly into proteins, the positive stranded DNA is used as a template for transcription into mRNA.
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What are the 2 types of capsids?
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1. Icosahedral
2. Helical |
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What is a capsomer?
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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.
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What is the shape of the capsid?
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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.
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What is a helical symmetry capsid?
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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. |
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What is the envelope?
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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". |
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Name 4 characteristics regarding how viruses are classified?
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1. Nucleic acid
2. Capsid 3. Envelope 4. Size |
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List 6 DNA viruses and their app. sizes.
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1. Parvoviridae(22nm)
2. Hepadnaviridae(42nm) 3. Papovaviridae(50nm) 4. Adenoviridae(80nm) 5. Herpesviridae(150nm) 6. Poxviridae(250nm) |
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List 9 RNA viruses and their app. sizes.
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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) |
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Most DNA viruses are double stranded, show icosahedral symmetry, and replicate in the nucleus. TRUE/FALSE
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TRUE.
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List three DNA viruses that are enveloped, and three that are naked.
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Enveloped viruses;
Herpes/Hepadna/Pox Naked; Papova/Adeno/Parvo |
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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
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TRUE.
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What are the 6 steps of viral replication?
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1. Adsorption
2. Penetration 3. Uncoating 4. Synthesis 5. Assembly 6. Release |
