REPLICATION How do we get more DNA Definition

REPLICATION: How do we get more DNA?

Definition: n The process of synthesizing a new strand of DNA.

When does it happen? During the ‘S’ (synthesis) phase of the cell cycle.

STEPS: n 1. Double Helix unwinds and unzips. The enzyme is called: n helicase.

HELICASE: an enzymes 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 complementary 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 DNA Molecule contains 1 strand from the old DNA and one strand of the new DNA.

STEPS: 3. Linkage of the sugar/phosphate backbone The phosphate and sugars 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 is this?

What is this? What are these parts?

Replication Bubbles DNA 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?