Virology review session: first midterm

By Philippe Perron Savard

Lecture 1

• Don’t bother. No questions will be asked.

Lecture 2: replication cycle

• Cells provide: ribosomes, nucleotides & aa, ATP (energy), membranes.

• Consequences of virus replication on the cells: – Diverts cell metabolism– Fill up the cells– Escape (lysis for example)– Apoptosis induction

Lecture 2: virus structure

• Some viruses affect the behaviour of their host to improve transmission

• A lot of viruses do not cause disease

Lecture 2: virus structure

• Techniques used to detect and measure viruses:– Electron microscopy– Hemagglutination– Plaque assay– Foci formation

• Replication cycle

Finding the pfu/ml

• If a dilution (1/10000) is made and 1 ml of this dilution is plated: we get 50 plaques.

• How do we solve this:

• 50 plaques in 1 ml of the dilution= 50 pfu/ml in that dilution.

• 50 pfu/ml * 10000 = 500 000 pfu/ml in the original solution.

Lecture 3: virus structure

• One step growth curve

• Baltimore classification

• Basics of virus particles

• Icosahedral and helical symmetry

Lecture 4: ssRNA phages

• Gene regulation dependent mostly on RNA secondary structure

• Replication Vs translation problem

• Replication

• Transcription of maturation gene

Fig 5 p. 41

Fig 6 p.42

Fig 7 p.42

Fig 8 p.46

Lecture 5: ssDNA phage (X174)

• Displays extensive overlapping in genes. How do we regulate transcription?

• Concept of frames in transcription

• Entry

• Replication through rolling circle

• Formation of the capsid

Fig 1 p.53

Different frame

• ACG ATG GGG CCC TAT GCT

• -1 AC GAT GGG GCC CTA TGC

• -2 CGA TGG GGC CCT ATG CT

• +1 TGG GGC CCT ATG CT

• +2 GGG GCC CTA TGC

Fig 3 p.56

Fig 4 p.56

Fig 5 p.58

T7 phage

• Entry and DNA winching by RNA pols from the host and the virus.

• How it regulates transcription of its genes

• How the T7 RNA pol functions

• Problems with replication of linear dsDNA

• pET vectors for protein expression

Fig 1 p.65

Fig 4 p.72

Lambda phage

• Genome organisation

• Understanding gene regulation is crucial

• How do we repress the lytic cycle?

• How do we decide between lysis or lysogeny

• Integration into the bacterial genome and its regulation

Fig 2 p.76

Fig 4 p.79

Fig 6 p.76

Fig 5 p.81

Fig 7 p.87