BAns Chap 13-14 II

1. Silencer can function downstream or upstream of promoter 

2. 3’ Poly (A) tail NOT 3’ cap 

3. Unwinding DNA = upregulate transcription

4. Binding of STFs are dependent on recognition of complementary shape between STF and binding sites (NOT recognition of histone tails) 

1. Capsid coat (NOT just capsid) 

2. Antigenic shift -> random assembly of RNA segments 

Describe role of viral DNA in infection process of T4 = what is DNA codes for! 

• Viral DNA acts as a template for… 

  • An enzyme that degrades the host cell’s DNA

  • DNA replication and transcription, using the host cell’s machinery to produce more copies of viral DNA and viral proteins

  • Lysozyme which breaks down the bacterial peptidoglycan cell wall, causing cell lysis and release of the intact bacteriophages

Advantages of lysogenic pathway 

• Viral DNA is integrated into the bacterial genome as a prophage, and is replicated together with the bacterial genome, without killing the host bacterium -> This allows the viral DNA to be replicated many times and passed to many bacteria cells, resulting in a large population of bacteria carrying the prophage

• Viral DNA can exit the bacterial genome when lytic cycle is triggered -> This allows the virus to escape from the host bacteria in unfavourable conditions

Function of haemagglutinin 

• Binds to specific receptors containing sialic acid on host cell so that the virus can enter the host cell via endocytosis

Properties of inhibitor 

• Inhibitor should have similar shape to the viral polyproteins -> complementary to the active site of HIV protease blocking the binding of substrate

Newly formed nucleocapsids…

Newly formed nucleocapsids recognises and moves towards cell surface membrane at exit point 

Effect of Ethanol on virus

• Ethanol is an organic solvent and dissolves the phospholipids bilayer of the viral envelope -> preventing the attachment and entry of the virus via fusion of membranes

+ RNA genome…

(+) RNA genome directly serve as mRNA template, synthesised by host ribosomes

Describe viral genome 

• Double-stranded DNA genome 

• Single-stranded RNA genome (Influenza)

  • Contains genes coding for viral proteins like RNA-dependent RNA polymerase

  • Template for the synthesis of complementary RNA strand (+) used as template for translation of viral proteins and synthesis of viral RNA

Label HIV

Evidence antigenic shift

• Different strains of virus need to infect the same host cell in the same organism

• Influenza pandemic caused by H2N2 did not happen in the same time period as H1N1 or H3N2

ANY Expression of proteins 

• This allows for long-term expression of proteins coded by the introduced RNA by host cell machinery using RNA polymerase and host cell ribosomes

Explain how virus acquires new viral envelope 

• Viral mRNA is translated into viral proteins by ribosomes at the RER and embedded into the membrane of the RER 

• Glycosylation of the viral proteins occurs at the RER/Golgi apparatus

• Transport vesicles with the embedded glycoproteins fuse with the cell surface membrane and are now part of the cell surface membrane

• The nucleocapsid will then be assembled near the cell surface, and it will bud off from the host cell membrane that is studded with the viral glycoproteins to form the viral envelope

1. Virus do NOT metabolise at all (even in host cells) 

2. Increased international travel -> does NOT change mosquito / environment -> it just increase number of cases NOT R0