Lecture 1 Flashcards
What is the ratio between viruses and cellular life?
10:1
How much viral DNA is in the human genetic material?
8%
How much viral DNA do human have in blood?
70%
How many bacteriophage particles in the ocean?
10^31
How much does a bacteriophage weigh?
10^-15 grams or 1 femtogram
How are viruses beneficial?
Catalyze movement of nutrients from organisms
Kill 20-40% of ocean microbes everyday
Transfer genes between organisms
Prevent and cure diseases
How did viruses advance cell biology research?
- Identification of promoters for eukaryotic RNA polymerases
- Cellular DNA replication enzymes
- Reverse transcriptase
- RNA-dependent RNA polymerases
- RNA splicing
- Translation
- Identification of oncogenes
What is a virus?
Infectious obligate intracellular parasite
What do virus particles contain?
Genetic material (DNA or RNA)
Capsid
Envelope (optional)
What are the two phases of a virus?
Inanimate phase (virion)
Multiplying phase
True or false: Viruses are passive
True: They are completely at the mercy of their environments. Viruses don’t actually “do” anything to infect
How were viruses first visualized?
Electron microscopy (1930s)
What are different physical attributes of a virus?
Nature/sequence of nuclei acid virion
Symmetry of capsid
Presence of envelope
Dimensions of virion and capsid
What is the envelope of a virus made of?
Lipid membrane
Taxonomy of virus?
Kingdom
Phylum
Class
Order
Family
Genus
Species
-virales is….
The order of the virus
-viridae is….
The family of the virus
-virus is …..
The genus of the virus
What is the infectious cycle of a virus?
- Binding to cell receptor
- Entry and uncoating
- Early gene expression
- Replication of viral genome
- Late gene expression
- Assembly of virions
- Exit
What determines tropism in viruses?
Cellular receptors are specific for each virus and host species
How do bacteriophages inject their genome into the cell?
Bacteriophages have special tails that drill holes and inject their genome into the host cell
How do plant viruses enter the cell?
Enter due to damage to the cell wall
How do animal viruses enter the cell?
Through membrane fusion or endocytosis
What is virus uncoating?
Capsid of virus disintegrates to release genome
What does the molecular pathway to early gene expression depend on?
Whether the genome is initially DNA, RNA, ds, ss, etc
What is the difference between early and late proteins?
Early: usually directs replication of genome
Late: typically structural proteins used to make viral particles
Enveloped viruses encode _____ that are inserted into ____ and direct formation fo the viral envelope upon release.
Glycoproteins
Lipid membranes
How do viruses exit the cell?
Lysis of cell
Budding (extrusion from cell membrane)
Enveloped viruses exit the cell by __
Budding
