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

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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

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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

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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

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TAHAP – TAHAP

REPLIKASI DNA

1.Denaturasi (Pemisahan) untaian DNA

template

2. Inisiasi

3. Pemanjangan untaian DNA

4. Ligasi fragmen DNA

5. Terminasi

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I

III III

I

DNA

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Replication of Strands

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Replication Fork

Point of Origin