Virology 2 ( Dr. Balfe): Your cells under new management Flashcards
Explain the Cheshire Cat escape strategy of the coccolithophore Emiliania huxleyi in response to viral infection.
- coccolithophore has carbonate shells which fix CO2. A single bloom fixes 10% in the UK
- Viruses control CO2 fixation in the ocean.
- Emiliania huxleyi carries a virus… in response to this infection it becomes a haploid to escape the virus. It does not have a carbonate shell in this form.
Do viruses contain ribosomes????
- NOPE
- they do not contain ribosomes because they do not undergo metabolism
Host cell receptors define what with respect to viruses?
- tissue tropism and species tropism
What are the majority of viruses classified as?
- RNA viruses aka Groups three, four, five and six. 3= dsRNA Viruses 4= + Sense RNA Viruses 5= - sense RNA viruses 6= RNA Reverse Transcriptase Viruses
How many viral particles do we breath in every day? What do they mostly comprise of?
- approx > 10,000
- Plant viruses
Explain the difference between antisense and sense strands.
- DNA is normally comprised of two strands an antisense strand and a sense strand. In dsDNA only one strand codes for the RNA that will be translated into protein - the antisense strand is the one that codes for the protein. The strand that does not code for the protein is called the sense strand. Another way of defining antisense DNA is that it is the strand of DNA that carries the information necessary to make proteins by binding to a corresponding messenger RNA. The antisense strand can also be called the noncoding strand.
Viruses that have a single stranded genome can be classified as what two groups?
- Positive strand Virus aka plus strand virus
- Negative strand virus aka minus strand virus
Explain positive strand Viruses.
- these viruses contain single stranded plus strand DNA genomes and transcription of it would yield a message of the minus sense. Therefore, before mRNA can be produced from Class 2 viruses, a complementary DNA strand must first be made to form a double stranded DNA intermediate. This process is called replicative form. The double stranded DNA intermediate is used for transcription and as the source of new genome copies - the plus strand becoming the genome while the minus is discarded.
What different kinds of strands can Negative-Strand RNA Virus genomes have?
- Simple : single piece of RNA that makes ONE protein
- Multipartite, simple
- Multipartite, simple, ambisense OR Multipartite, complex, ambisense
With Negative Strand RNA virus genomes can a naked one make a virus?
- nope
- it needs RNA poly to make a positive strand,
Explain some features of positive strand RNA viruses.
- naked RNA CAN form viruses
- can have a conventional cap and tail or one or the other or neither
- genomes are easily broken
- they have a beginning and end
- end= poly a tail
- they make two sorts of proteins ( those that go into the virus and those that dont ie non structural and structural proteins. RNA genomes are extremely small.
What genes are commonly present in RNA Virus genomes? How many genes = typical number?
- RNA polymerase
- Trimeric envelope
- Glycoprotein subunits
- Nucleoprotein
- usually manage with X
What does myxo mean in myxoviruses?
- mucus aka these are the cold viruses
Myxoviruses all encode what?
- haemagglutinin
L> a glycoprotein found on the surface of the influenza viruses. It is responsible for binding the virus to cells with sialic acid on the membranes, such as cells in the upper respiratory tract or erythrocytes.[1] It is also responsible for the fusion of the viral envelope with the endosome membrane, after the pH has been reduced. The name “hemagglutinin” comes from the protein’s ability to cause red blood cells (erythrocytes) to clump together (“agglutinate”) in vitro.[2]
Why were the myxoviruses split by the Baltimore classification?
- some had a single stranded antisense viral genome
- others were multipartite genetic organization with structural complexity. Ex: Influenza virus genome has multiple messages and multiple parts
