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Agenda:
Warm Up
DNA Replication Notes (TOC#__)
Edible DNA Replication Activity
Homework:
Complete Lab Questions
Complete study guide for the quiz on friday
Purpose: Explore DNA replication, what it is, where it occurs and how it takes place.
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Warm Up 4/4
If there is 30% Adenine in a DNA molecule, how much Cytosine is present?
How do you think new DNA could be made?
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Answer:
There would be 20% Cytosine
Adenine (30%) = Thymine (30%)
Guanine (20%) = Cytosine (20%)
Therefore:
60% A-T and 40% C-G
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DNA Replication
What
Why
Where
How
Steps of Replication
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DNA Replication WHAT
What:
Making a copy of the DNA
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DNA Replication - WHAT
Model: Semiconservative Model of Replication
Idea presented by Watson & Crick
The two strands of the parental molecule separate, and each acts as a template for a new complementary strand
New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA
Parental DNA
DNA Template
New DNA
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DNA Replication WHY
2. Why:
Because we need to make more DNA for new cells
DNA has to be copied before a cell divides
New cells will need identical DNA strands
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DNA Replication WHERE
3. Where:
Nucleus of eukaryotes
Because that is where the DNA is
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DNA Replication HOW
4. How:
Begins at Origins of Replication
Two strands open forming Replication Forks (Y-shaped region)
New strands grow at the forks
Replication
Fork
Parental DNA Molecule 3’ 5’
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DNA Replication HOW
As the 2 DNA strands open at the origin, Replication Bubbles form
Prokaryotes (bacteria) have a single bubble
Eukaryotic chromosomes have MANY bubbles
Bubbles
Bubbles
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11. DNA Replication - Process
Large team of enzymes coordinates replication
Enzymes
more than a dozen enzymes & other proteins participate in DNA replication

12. How: Replication: 1st step
Unwind DNA
helicase enzyme
unwinds part of DNA helix
by breaking the weak hydrogen bonds between the nitrogenous bases
single-stranded binding proteins
replication fork
helicase

13. HOW: Replication: 2nd step
Build daughter DNA strand
DNA polymerase III: adds new complementary bases
DNA
Polymerase III

14. 3rd step: Proofreading New DNA
DNA polymerase initially makes about 1 in 10,000 base pairing errors
Enzymes proofread and correct these mistakes
The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors
What do you notice about enzyme names?
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15. Activity: Edible DNA and Replication
Objectives:
Students will learn and demonstrate the structure and function of DNA, an essential
component of any cell.
Materials:
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16. Activity: Edible DNA and Replication
Part I: Building a DNA Model
1. Use a diagram of DNA (you could use the DNA Coloring sheet!) and the key below to build four different nucleotides

17. Groups of 4 2 Construction workers 1 reader 1 supply manager
Build the models
1 reader
Read the lab together (read all the questions too)
1 supply manager
Get all the supplies for the group
4 note takers/Cleaners
You are each responsible for turning in a lab and making sure your station is clean