1. DNA Replication
Biology
Mrs. Harper
2/13/18

2. February 13, 2018
Download notes
Begin working on Do Now

3. Do Now 12/1/15 Who was the first person to get a photograph of DNA?
Which scientist(s) discovered the double helix structure?
Besides DNA, what did some scientists believe to be the heredity molecule?
What did Gregor Mendel discover?
Which three scientists made their discovery in 1944?
What are the three parts of a nucleotide?
What does DNA stand for?

4. DNA Replication

5. DNA Replication What is the purpose of DNA replication?
To copy genetic material
Occurs during S phase of interphase

6. Complementary Base Pairing (makes replication possible)
Adenine pairs with Thymine
Guanine pairs with Cytosine
Bases form weak hydrogen bonds T A G C
copyright cmassengale

7. Semi-Conservative Replication
One side of DNA is the template (old strand) and one side is the complementary (new strand), this is called semi-conservative replication

8. Antiparallel Strands
Strands move in opposite directions (5’ to 3’ or 3’ to 5’)
Sugars are connected to phosphates through COVALENT BONDS.
copyright cmassengale

9. Single ring PYRIMIDINES 1.Thymine (T) 2.Cytosine (C)
Nitrogenous Bases (Purines only pair with pyrimidines because otherwise the helix would be too wide)
Double ring PURINES
1.Adenine (A)
2.Guanine (G)
Single ring PYRIMIDINES
1.Thymine (T)
2.Cytosine (C)
A or G
T or C
copyright cmassengale

10. DNA P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A
copyright cmassengale

11. DNA Replication Origins of replication
1. Replication Forks: site where new DNA strands start growing
Replication
Fork
Parental DNA Molecule 3’ 5’

12. DNA Replication Strand Separation:
1. Helicase: enzyme which catalyzes the unwinding and separation (breaking the hydrogen bonds) of the parental double helix.
2. Single-Strand Binding Proteins: proteins that help keep the separated strands apart.

13. DNA Replication Synthesis of the new DNA Strands:
1. DNA Polymerase: with a RNA primer in place, DNA Polymerase (enzyme) catalyze the synthesis of a new DNA strand in the 5’ to 3’ direction.
RNA
Primer
DNA Polymerase
Nucleotide 5’ 3’

14. DNA Replication
2. Leading Strand: synthesized as a single polymer in the 5’ to 3’ direction.
RNA
Primer
DNA Polymerase
Nucleotides 3’ 5’

15. DNA Replication
3. Lagging Strand: also synthesized in the 5’ to 3’ direction, but discontinuously against overall direction of replication.
RNA Primer
Leading Strand
DNA Polymerase 5’ 3’
Lagging Strand 5’ 3’

16. DNA Replication
4. Okazaki Fragments: series of short segments on the lagging strand.
Lagging Strand
RNA
Primer
DNA
Polymerase 3’ 5’
Okazaki Fragment

17. DNA Replication
5. DNA ligase: a linking enzyme that catalyzes the formation of a covalent bond from the 3’ to 5’ end of joining stands.
Example: joining two Okazaki fragments together.
Lagging Strand
Okazaki Fragment 2
DNA ligase
Okazaki Fragment 1 5’ 3’

19. Question: DNA 5’-GCGTATG-3’
What would be the complementary DNA strand for the following DNA sequence?
DNA 5’-GCGTATG-3’

20. Answer:
DNA 5’-GCGTATG-3’ (Old)
3’-CGCATAC-5’ (New)

21. Correct Answer Problem #1
5’ ACTGA 3’ Old Strand
3’ TGACT 5’ New Strand
Problem #2
5’ CTAAG 3’
Find its complementary new strand

22. Correct Answer Problem #2
5’ CTAAG 3’ Old Strand
3’ GATTC 3’ New Strand
Problem # 3:
5’ GCATA 3’
Find its complementary strand

23. Correct Answer Problem #3
5’ GCATA 3’ Old Strand
3’ CGTAT 5’ New Strand

24. Nucleotide

25. Assignment Complete the worksheet independently on CODE RED.
Unfinished classwork is homework
In a couple minutes, we will begin our activity creating a DNA model.

26. Creating DNA Models
We will create DNA models using the supplies provided in the bag.
The twizzlers will represents our sugar-phosphate backbone.
The toothpicks will be the hydrogen bonds holding the bases together.
Red/orange gummies = Adenine (A)
Blue gummies = Thymine (T)
Green gummies = Guanine (G)
Yellow gummies = Cytosine (C)
Build your model. Once finished, raise your hand so I can check to make sure you have the correct sequence to receive credit.
You may then eat your model or throw it away at the END of class.

27. DNA Model Hydrogen bonds (toothpicks)
Sugar-Phosphate Backbone (twizzlers)
**Make sure you pair each base with its proper pair! Remember the pairing rules!
Nitrogen bases
(gummy bears)