1. DNA Replication Notes
Unit 5

2. RECALL: DNA is made up of two complementary strands.
Chargaff’s Rules deem that A=T and G=C
The nitrogen bases are held together by hydrogen bonds
The backbone is made of sugars and phosphates

3. What is Replication?
Replication- process that occurs in order to copy entire chromosomes in preparation for cell division and put genetic material into daughter cells equally

4. When does it occur?
In Eukaryotic cells DNA replication occurs during Interphase

5. DNA Replication occurs at replication forks.
The DNA is “unzipped” by an enzyme called helicase.
Helicase breaks the hydrogen bonds that hold the bases together “like scissors”.
helicase
primase
DNA polymerase

6. Better view of unzipping

7. It also proofreads its work, to avoid mistakes in replication.
Next, Primase gets the strand ready, so that DNA polymerase can do its job…
DNA polymerase adds nucleotides to the strand, creating a double-stranded DNA molecule that is a copy of the original.
helicase
primase
DNA polymerase
It also proofreads its work, to avoid mistakes in replication. A

8. DNA Polymerase adding free nucleotides

9. What do we have now?

10. This is why replication is semiconservative.
This means that each new strand of DNA created is half parental or “old” DNA and half new DNA.

11. Big picture…1 nucleus replicated its genetic material, then the nucleus and cytoplasm divided and 2 genetically identical daughter cells resulted
Parent Cell
Genetically Identical Daughter Cells

13. Label the diagram
Word Bank: Nucleotide Primase Helicase DNA Polymerase

14. The bases are held together by hydrogen bonds.
Nitrogenous Bases
Adenine pairs with Thymine (A with T)
Cytosine pairs with Guanine (C with G)
The deoxyribose sugar and the phosphate group combine to make up the sugar-phosphate backbone
The bases are held together by hydrogen bonds.