1. Unit 4 Part 1
DNA Replication

2. Review of DNA structure
Nucleotides: (3 Parts)
Phosphate group
5 Carbon sugar
Sugars and phosphate are held together by a covalent bond.
Nitrogen base
There are 4 nitrogen bases – Hydrogen bonds
Adenine Guanine
Thymine Cytosine
Name: Deoxyribonucleic Acid
Shape: Double Helix
Function:
Basis for all living things
Makes proteins which make traits eye color, nose shape, heart function.
Structure: Made up of repeating units called nucleotides.

3. Nitrogen Bases
Nitrogen bases pairing together is what makes the double helix shape.
The 4 nitrogen bases are grouped together
Pyrimidines
Cytosine
Thymine
Purines
Adenine
Guanine
Only a purine can pair with a pyrimidine
Adenine – Thymine
Guanine – Cytosine

4. Complementary Bases
In order to make the double strand the N-bases pair up with an existing strand:
What would the complementary strand be for the following DNA sequence:
AAA TCG GTA CCA TGA CAG GCC TGC AAT
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5. DNA Replication
1. The Double Helix unwinds and unzips by breaking the Hydrogen bonds between the nitrogen bases.
An enzyme called DNA Helicase does this.
2. The 2 strands separate and form a replication fork .
Place where the new nucleo.tides will be added.

6. DNA Replication cont’d.
3. New nucleotides are added to the unwound strands (template or parent strands) following the base pairing rules.
DNA Polymerase does this.
4. As DNA polymerase moves along the strands, 2 new double helixes are formed.
5. Enzymes continue adding nucleotides until it reaches a signal for it to detach.

7. DNA Replication Review
Occurs during the S phase of interphase.
Process by which 2 identical strands of DNA are created.
First the double helix unwinds and unzips-DNA Helicase.
New nucleotides are added to the existing strands.
DNA replication is complete.
Once the DNA (chromatin) condenses into chromosomes they would be replicated chromosomes.

8. DNA Replication Video
DNA Replication Video