replication:
DESCRIPTION
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 PresentationTRANSCRIPT
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?
The bases bond by H-bonding
STEPS: 4. After 2 new
ladders are formed, each
ladder twists to form 2 new double helices.
What is this?What are these parts?
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?