L20 DNA replication Flashcards
what are the genome replication sites of in eukaryotic cells
nucleus (most DNA viruses)
cytoplasm (few, pox virus)
what are the viral genome replication sites in prokaryotic cells
cytoplasm
what enzymes/structures involved in DNA replication
DNA dependent DNA polymerase
DNA dependant RNA polermerase
ribsome
steps of the DNA replication
DNA is transcribed into mRNA
mRNA is translated into proteins
what enzyme is used for the replication of the DNA
DNA dependant DNA polyermase
what enzyme is used during transcription
RNA dependant DNA polymerase
what structure is used during translation
ribosome
what host factors does the virus use to replicate
always ribosome and RNA dependant DNA polymerase
sometimes DNA dependent DNA polymerase
describe synthesis of viral proteins (gene expression) in DNA viruses
-not all genes are expressed at the same time, they’re sequentially expressed
what are the three types of genes (gene expression)
immediate/early genes
early genes
late genes
when are the immediate-early genes transcribed
as soon as the virus is within the cell
what kind of proteins do the immediate genes transcribe
alpha mRNA
what does alpha mRNA translate to
alpha proteins
viral linear dsDNA replication examples
T4 phage, gamma phage, herpes virus, poxvirus
how do dsDNA viruses replicate (4)
concatemers formed after replication (T4 phage)
close ends by covalent bonds (pox virus)
circularising DNA before replication (herpesvirus)
using a viral protein for priming for replication
what is a concatemer
long DNA molecule consisting of two or more DNA genomes linked together
how are genomes of a concatemer linked
successive homologous recombination events
how are concatemers resolved
host endonuclease nicks it into individual genomes and packed into the virion
how are concatemers resolved
host endonuclease nicks it into individual genomes and packed into the virion
how are ends closed using covalent bonding
host helicase nicks closed-end
3’ prime ends form a hair loop and acts as a primer for RNA primer-independent replication
polymerase begins replication using itself as a template
2 genome concatermor is formed
explain the process of circulising DNA replication
cohesive or blunt ends of DNA form a circle
helicase creates a nick, 3’ end is the primer
RNA primer independent replication of one strand occurs using the inner strand as a template
once one strand is replicate the outer strand is displaced and complementary synthesis begins (fragments)
explain the process of using a viral protein as a primer
RNA and DNA independant replication
viral protein interacts and forms complex with polymerase
complex binds to 3’ end of one strand and begins synthesis
other strand is displaced and DNA binding protein (DBP) attaches and forms a circle
polymerase starts synthesis on the displaced strand which removes the DBP
what kind of virus uses a viral protein primer method of replication
adenovirus
how does linear ssDNA replicate in viruses
the palindromic end of DNA form a hair pin
3’ prime end serves as a primer
replisome pushes through and flattens the 5’ end
nuclease nicks the DNA of the bottom strand
The 3’ prime end again acts as a primer and the top strand is used as a template forming a dsDNA intermediate
The upper strand folds into genomic DNA and the bottom begins the cycle again
example a virus that has linear ssDNA
parvovirus
how many types of DNA replication are there and what are they
linear ssDNA
linear ds DNA
circular dsDNA
circular ssDNA
how many types of linear dsDNA replication is there
4
how many types of linear ssDNA are there
1
example of circular dsDNA replication
SV40
what enzyme is the viral T antigen in circular dsDNA replication
helicase
stages of circular dsDNA replication
initiation
elongation
decatenation
what happens during initiation
recognition by T antigen (helicase)
unwinding begins
what happens during elongation
multiprotein replication complex begins to add bases in a bi-directional fashion
what happens during decatenation
Topoisomerases decatenates the two genomes
example of virus that uses circular ssDNA replication
oX174 phage
