S1: DNA Synthesis Flashcards
How is DNA replication described as?
Semi-conservative
What is the replication origins?
Specific sites where DNA replication is initiated
What recognises the replication origins?
Initiation complexes
Why does DNA at the origin unwind to form a replication bubble?
Allow access to the replication machinery
What phase of the cell cycle does DNA synthesis occur in?
(S) phase
It involves complete unwinding of the parental DNA
How long is the bacterial cell cycle and phases does it include?
20-30 minutes
M phase- S Phase
How long is the mammalian cell cycle and phases does this include?
16-24 hours
M Phase - G1- S - G2
Why is the mammalian cell cycle longer than the bacterial cycle?
Human have more chromosomes
Compare the number of replication origins in bacteria and mammalian cells
Bacteria DNA only has a single replication origin
Eukaryotic cells DNA replication initiates at multiple replication origins
What is DNA polymerase?
This is the enzyme that synthesises DNA and cells have multiple DNA polymerases
Name the types of polymerases and function in eukaryotic cells
Alpha – replication Beta – replication Gamma – mitochondrion Delta – replication (causes elongation) Epsilon – replication (causes elongation)
List the key properties of DNA polymerases
- Acts in 5’ to 3’ directions
- Utilises AT and CG base pairing to synthesise new DNA strands
- It requires a DNA template = a DNA or RNA primer, the four dNTP and Mg2+ ions
- Proof reading function
What does dNTP stand for?
Deoxyribosenucleoside triphosphate
Why does DNA polymerase require a DNA template?
DNA polymerase requires an -OH on the 3’ carbon to start adding nucleotide (building blocks can only be added to the 3’ end).
What are the building blocks for DNA?
dNTPs