Powerpoint 17: Viruses Flashcards
What are the different groups of viruses that exist?
Group 1: double stranded DNA +/-
Group 2: single stranded DNA +
Group 3: double stranded RNA +/-
Group 4: single stranded RNA +
Group 5: single stranded RNA -
Group 6: single stranded RNA + , reverse transcription
Group 7: double stranded DNA +/- , reverse transcription
Is purified negative single stranded RNA infective?
No
It must be converted to positive sense RNA by RNA polymerase before translation.
Complementary to mRNA.
What is an ambisense virus?
Virus resembles a negative single sense stranded RNA but they can also translate genes from the positive strand.
What are the two characteristics of an enveloped virus?
1) lipid bilayer membrane
2) impermeable barrier between their genomes and the outside environment
What are 2 examples of enveloped viruses?
HIV and influenza
What are 2 examples of non-enveloped viruses?
Poliovirus and Papillomavirus
What are 2 characteristics of non-enveloped viruses?
No membranes
No barrier so require a tightly packed protein shell to exclude nucleases or other sources of genetic damage.
What are the steps in the virus entry and uncoating?
Binding to extracellular membrane Signaling Internalization Penetration Intracytosolic transport Uncoating Entry to the nucleus
What are the 2 unique ways the RNA viruses replicate?
1) RNA dependent RNA synthesis - RNA replication
2) RNA dependent DNA synthesis (reverse transcription followed by DNA replication and transcription.
What must all viruses do to make essential viral proteins?
express their genes as functional mRNA
Is mRNA defined as + or - ?
As positive sens RNA
What is the average range of virus Kb?
most between 5 and 15
-few greater than 30
