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REPLIKASI DNA
Dr. Oeke Yunita, S.Si., M.Si., Apt. 1
Synthesis Phase (S phase)
• S phase during interphase of the cell cycle
• Nucleus of eukaryotes
2
Mitosis -prophase -metaphase -anaphase -telophase
G1 G2
S phase
interphase
DNA replication takes place in the S phase.
Handout Biologi Sel, Dr. Oeke Yunita
DNA Replication
• Begins at Origins of Replication
• Two strands open forming Replication Forks (Y-shaped region)
• New strands grow at the forks
3
Replication Fork
Parental DNA Molecule
3’
5’
3’
5’ Handout Biologi Sel, Dr. Oeke Yunita
Template: double stranded DNA
Substrate: dNTP
Primer: short RNA fragment with a
free 3´-OH end
Enzyme: DNA-dependent DNA
polymerase (DDDP),
other enzymes,
protein factor
DNA replication system
4 Handout Biologi Sel, Dr. Oeke Yunita
Origin of Replication Enzymes (Initiator Proteins) recognize the start site on template DNA and initially open up the DNA (single strands)
Helicases untwist the double helix at the replication forks
Primase begins DNA replication by laying an an RNA primer (10 nt long) for DNA polymerase to start at
Single-strand binding proteins bind to and stabilize the single-stranded DNA until it can be used as a template
DNA polymerase polymerizes new DNA in a 5’ to 3’ direction, proofreads the newly laden DNA, excises error ridden DNA and replaces that DNA with the correct sequence. Speed/fidelity: mutates 1 X 10-10
Topoisomerase corrects “overwinding” ahead of replication forks by breaking, swiveling, and rejoining DNA strands
Terminal replication proteins stall replication fork progress for polymeriation to catch-up
DNA ligase anneals nucleotides together, creating a DNA strand
Players involved in DNA Replication
5 Handout Biologi Sel, Dr. Oeke Yunita
TAHAP – TAHAP
REPLIKASI DNA
1.Denaturasi (Pemisahan) untaian DNA
template
2. Inisiasi
3. Pemanjangan untaian DNA
4. Ligasi fragmen DNA
5. Terminasi
6 Handout Biologi Sel, Dr. Oeke Yunita
I
III III
I
DNA
9 Handout Biologi Sel, Dr. Oeke Yunita
Replication of Strands
Handout Biologi Sel, Dr. Oeke Yunita 10
Replication Fork
Point of Origin
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