HS Science Concept Presentation

DNA Replication

Roberta SiuJuly 22, 2010

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

Grade 12 Biology Overview

DNA replication

Who are your students?

ScienceSNC1D

Grade 9, Academic

ScienceSNC2D

Grade 10, Academic

BiologySBI3U

Grade 11, University

BiologySBI4U

Grade 12, University

Prerequisite

Note: Grade 11 Chemistry is not required.

What do your students know? Grade 10 Science

Unit: Tissues, Organs, and Systems of Living Things

Grade 11 Biology

Unit: Genetic Processes

From On Science 10, McGraw-Hill Ryerson 2009

From Biology 11, McGraw-Hill Ryerson 2010

DNA Replication:Placement in the Unit

Molecular Genetics

DNA Replicatio

n

Protein Synthesis

Biotechnology

STSE issues related to Genetics

Big Ideas

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).

DNA Replication:Overview of Concept

DNA Replication:Overview of Concept

http://highered.mcgraw-hill.com/sites/0072507470/sitemap.html

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?

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”)

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.

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:

http://learn.genetics.utah.edu/content/labs/extraction/

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.

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.”

Student Difficulties/RoadblocksRoadblock #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.

Student Difficulties/RoadblocksRoadblock #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.

Student Difficulties/RoadblocksRoadblock #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

Practical Applications & Societal Implications

DNA Replication

DNA fingerprinting(forensics)

maternity/paternity testing

genetically modified food (agriculture)

insulin production(medicine)

cloningPCR(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.