1. HS Science Concept Presentation DNA Replication
Roberta Siu
July 22, 2010

3. Presentation Outline Placement of this Concept
Who are your students & What do they know
Curriculum Expectations
Concept Overview
Class Activities
Lesson Sequence
Student Difficulties/Roadblocks
Societal Implications & Practical Applications
Resources

4. Grade 12 Biology Overview
DNA replication

5. Who are your students? Prerequisite Science SNC1D Grade 9, Academic
Biology
SBI3U
Grade 11, University
Biology
SBI4U
Grade 12, University
Note: Grade 11 Chemistry is not required.

6. What do your students know?
Grade 10 Science
Unit: Tissues, Organs, and Systems of Living Things
Grade 11 Biology
Unit: Genetic Processes

7. From On Science 10, McGraw-Hill Ryerson 2009

8. From Biology 11,
McGraw-Hill Ryerson 2010

9. DNA Replication: Placement in the Unit
Big Ideas
Molecular Genetics
STSE issues related to Genetics
Biotechnology
Protein Synthesis
DNA Replication

10. DNA Replication: Curriculum Expectations
D1.1 Analyse, on the basis of research, some of the social, ethical, and legal implications of biotechnology.
D2.1 Use appropriate terminology related to molecular genetics, including, but not limited to: polymerase I, II, and III, DNA ligase, helicase, Okazaki fragment, mRNA, rRNA, tRNA, codon, anticodon, translation, transcription, and ribosome subunits.
D2.3 Conduct an investigation to extract DNA from a specimen of plant or animal protein.
D3.1 Explain the current model of DNA replication, and describe the different repair mechanisms that can correct mistakes in DNA sequencing.
D3.7 Describe, on the basis of research, some of the historical scientific contributions that have advanced our understanding of molecular genetics (e.g. discoveries made by Frederick Griffith, Watson and Crick, Hershey and Chase).

11. DNA Replication: Overview of Concept

12. DNA Replication: Overview of Concept

13. Class Activities Some things to consider:
1) What do you like and not like about this activity?
2) What type of students is this activity designed for?
3) How can this activity be used to help students overcome learning difficulties?

14. Lesson Sequence Day 1: DNA Structure
Diagnostic: Find out what students know about DNA.
Chalk & Talk + visuals
Simulation of antiparallel nature of DNA strands using students
Building DNA model
-using modeling kits or
-using edible items (e.g. candies)
-do on-line simulation (Gizmo: “Building DNA”)

15. Lesson Sequence Day 2: History of DNA
Jig-saw activity: students will learn the scientific contributions by key scientists that led to our understanding of DNA structure and function in this student-led group sharing and learning format.

16. Lesson Sequence Day 3: DNA Extraction Lab
Students will conduct lab in groups of 2 or 3.
Teachers can assess students for safe and appropriate use of lab equipment and scientific investigation skills.
Alternatively, if materials or time is limited, you may have students complete virtual lab:

17. Lesson Sequence Day 4: DNA Replication
Inquiry demo: Two strings twisted together to simulate a DNA molecule, ask students what needs to occur in order to begin replicating this DNA.
Chalk & Talk + visuals
Show animation of process.
Have students summarize key events in the DNA replication process in flowchart format.

18. Lesson Sequence Day 5: Review and Reinforce Concepts
*Look for student difficulties or misconceptions.*
Veritech tiles review activity
Paper DNA replication simulation activity
Exit Card:
Tell me “one thing you have mastered
and one thing you are still unclear about.”

19. Student Difficulties/Roadblocks
Roadblock #1: Confusion around the directionality of DNA strands.
i.e. antiparallel orientation where one strand runs in the 5’to 3’ direction, while the other runs in the 3’ to 5’ direction.
Strategies: Use visuals and simulations.

20. Student Difficulties/Roadblocks
Roadblock #2: Differences between replication of the leading strand vs the lagging strand. (“Both DNA strands have a 5’ and a 3’ end, why are they replicated differently?”)
Strategies:
-emphasize that DNA polymerase III can only synthesize new complementary DNA strand from the 5’ to 3’ direction
-instead of showing them the true model of how it works, ask students to think like scientists and try to explain how both DNA strands can be synthesized
-ask students to draw a series of diagrams representing snapshots of the process.

21. Student Difficulties/Roadblocks
Roadblock #3: A lot of new terms!
(“Do I have to memorize everything?”)
Strategies:
-create vocabulary list
-for enzymes, look at the root of the word before the “ase” ending and that often will give you a hint as to the function of the enzyme.
For example: When you see helicase, you should think of helix, so this enzyme must be responsible for unwinding the helix before DNA can be replicated.
-use graphic organizers to break large concept into small chunks

22. Practical Applications & Societal Implications
DNA fingerprinting
(forensics)
maternity/paternity testing
DNA Replication
PCR ?
genetically modified food (agriculture)
PCR(polymerase chain reaction) is a technique that has allowed us to make many copies of a desired DNA sequence from just a small DNA sample.
cloning
insulin production
(medicine)