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Cells
DNA REPLICATION
Aims:
 Describe the semi-conservative model of DNA replication
 Summarize and model the steps of DNA replication
 Explain how the structure of DNA enables it to replicate efficiently
Agenda:
 T&T
 Diagram Debrief
 Animation
 Notes
 Modeling Activity
 Test Wizard
Engage: Tell students that we have now explored in depth most of the eukaryotic cell, from mitochondria
and chloroplasts to the cell membrane, ribosomes and lysosomes. But what part of the cell ultimately
controls all of these other organelles and components? Elicit the nucleus, which contains DNA, the
instructions. Tell students that each of their cells contains 6 billion base pairs of DNA and that new cells in
their body are constantly made. Where does this DNA come from? After students turn, talk and share,
elicit that the DNA comes from other DNA through DNA replication to ensure that all cells have their own
copy of genetic information to run the cell. Since a cell can copy all 6 billion base pairs in a few hours,
with only few mistakes (one base per several billion) DNA replication must be pretty efficient.
Explain
 Diagram debrief
 Structure of DNA
Explore
 Give pairs baggie with materials
 Have students build DNA molecule that is four base pairs long
 Have students race to copy molecule
 Have students share techniques, discuss ways to improve the process
 Students choose which model works best. Elicit semi-conservative and explain why.
Explain
 Now that we know the overall strategy, let’s look at the details of the process
 Students observe DNA animations independently:
 http://www.lewport.com/10712041113402793/lib/10712041113402793/animations/DNA%20Replication%20%20long%20.html,
 http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf
 Students compare to the model they created and summarize step in notes
 Debrief notes under doc cam
Extension: Application questions
Evaluate: MC questions question
Homework: Annotation on protein synthesis
Cells
DNA REPLICATION
Do Now
1. Give the diagram a caption and annotate it.
2. If the molecule above were RNA, how would its structure differ?
Replication Race
1. White = phosphate, small white = H bond, black = sugar, blue = A, green = T, yellow = C, orange = G.
2. Build a DNA molecule containing 4 base pairs.
3. Compare your molecule to another group. How is it different? Why is this important?
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4. When signaled, replicate your molecule as fast as you can. Raise your hand when done.
5. What made your technique effective/ineffective?
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3. Based on this activity, which diagram below illustrates the most EFFICIENT model for DNA replication?
Explain your choice.
DNA REPLICATION
Cells
Explaining DNA replication
1. Watch DNA replication using the Animation links on the blog.
2. As you watch, summarize the steps to DNA replication IN YOUR NOTES.
3. In your notes, explain one THEME that DNA replication illustrates
Extension
1. Circle the model(s) that correctly show DNA replication. Explain your choice.
2. Imagine you are an enzyme copying a strand of DNA. Determine the complementary sequence
for the following DNA strand:
ACCTAGCGGGATCATT
3. If a DNA molecule consists of 30% A, what is the percentage of other bases in the DNA molecule?
4. Put the steps of DNA replication in order:
___ Enzyme adds complementary nucleotides to original DNA strands
___ Enzyme unwinds DNA helix
___ Two identical DNA molecules form, each containing one parent and one daughter strand
___ Enzyme unzips DNA by breaking hydrogen bonds
5. Your body constantly makes new cells to replace old or damaged cells. Where does the DNA in
these new cells come from? Explain fully.
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Cells
Exit Slip
DNA REPLICATION
Cells
DNA REPLICATION
INDEA REVIEW
A student conducted an experiment in which she put identical pieces of plant tissue in solutions of
different molarity (concentration) for 24 hours and then measured the change in mass in the plant
tissue. Her results are shown below:
Discuss the results shown in this graph using your knowledge of cellular processes.
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Cells
DNA REPLICATION
AP Exit Slip
Scientists seeking to determine which molecule is responsible for the transmission of characteristics from
one generation to the next knew that the molecule must be able to copy itself quickly and precisely.
Explain how DNA meets these criteria using your knowledge of DNA structure. The following words may be
helpful:
DNA
Replication
Enzymes
Complementary
Nucleotides
Hydrogen bonds
Unwind
Unzip
Old strand
Proofread
New strand
Identical
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Cells
DNA REPLICATION