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REPLICATION:. How do we get more DNA?. Definition:. The process of synthesizing a new strand of DNA . When does it happen? During the ‘S’ (synthesis) phase of the cell cycle. STEPS:. 1. Double Helix unwinds and unzips. The enzyme is called: . helicase . - PowerPoint PPT Presentation
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REPLICATION:
How do we get more DNA?
Definition:
The process of synthesizing a new strand of DNA .
When does it happen? During the ‘S’ (synthesis) phase of the cell cycle.
STEPS:
1. Double Helix unwinds and unzips. Theenzyme is called:
helicase.
HELICASE: an enzyme that breaks the hydrogen bonds between the base pairs.Result: DNA molecule separates into two nucleotide strands, single stranded DNA.
As the double helix unwinds we get the “replication fork”:
STEPS: 2. Pairing of
new nucleotides to old nucleotides.
DNA POLYMERASES are enzymes that move along each strand, adding free-floating nucleotides to the exposed bases according to complimentary matching.The original DNA strand acts as a “template”
The new nucleotides are added in the “replication fork”
Both sides of the replication fork are adding nucleotides at the same time.
Replication is considered “semi-conservative”
each DNAmoleculecontains 1 strandfrom the old DNAand one strand ofthe new DNA.
STEPS:
3. Linkage of the
sugar/phosphate backbone
The phosphate andsugars of each nucleotide bond to complete the sides of the ladders.
Is this semi-conservative?
STEPS: 4. After 2 new
ladders are formed, each
ladder twists to form 2 new double helices.
Replication BubblesDNA is unzipped along many points that grow larger as replication progresses in both directions
We have now gone from one copy of DNA to two!:
….exactly the same as the original!
How is each new molecule related to the original?
