DNA Replication (AIG IRP)

DNA Replication (AIG IRP)

Lesson Overview

Brief Description of Lesson/Task/Activity: The task has two parts. Part 1 is answering questions about DNA replication to ensure that students can construct their own understanding of DNA replication, and the second part is to create a product modeling DNA replication.

This task can be used as an introduction to DNA and protein synthesis or before the subject is taught so that the students can develop their own understanding and questions about the role and process of DNA replication.

Time Frame: 5-7 days

Type of Differentiation for AIGs:

  • Enrichment
  • Extension
  • Acceleration

Adaptations for AIGs:

  • Content
  • Process
  • Product

Explanation of How Resource is Appropriate for AIGs: This task requires the student to move beyond the regular curriculum, develop an understanding of the relationship between all of the proteins involved in DNA replication, transfer their knowledge to a product to explain the concept to other students, answer higher level questions, incorporate independent study, and use creativity in the development of their model.

Needed Resources/Materials:

  • Computer with internet
  • Materials to make the model-poster board or science fair board, variety of craft supplies or variety of types of candy (Twizzlers work well for DNA strands)


Teacher Notes: The websites listed above are only a few of the sites that students can use; they are only suggestions. If students are given these, you may want to require that they find 2 more sources on their own. Please also note that many of them require Adobe Flash Player, which will no longer be supported after December 2020.

Stage 1: Engage

DNA makes us who and what we are! In order for all of cells to function and make us who we are, DNA must replicate each time new cells form or divide.

DNA can replicate in human cells up a rate of 50 nucleotides per second! This is actually slow compared to prokaryotes, which replicate at a rate of up to 100 nucleotides per second. Why do you think prokaryotes are able to replicate faster? (hint:  compare chromosome structures) Before we can understand how DNA makes us “us,” we need to understand how it replicates. The number of “parts” used in DNA replication is amazing. All of the proteins and nucleotides must be ready at a specific time. In this task, you will generate your own understanding of how all of the parts work together to make a new DNA strand.

Stage 2: Elaborate

If this is assigned as an individual out of class task- have the students answer the following questions using the above websites, other websites they find or an AP level text. If assigned to a group of 3-4 students, allow students to use a computer to answer the following questions.

Once students have answered the questions(either as individuals or as a group), use the questions as a guideline for a class discussion on the details of the process of DNA replication.

Part 1- Questions

  1. Explain the purpose of DNA replication.
  2. Summarize the general process of DNA replication
  3. Explain why DNA replication is called semi-conservative.
  4. Explain what a replication fork is and why they are critical to DNA replication.
  5. Write a brief outline of the steps involved in DNA replication.
  6. Describe the role of Okazaki fragments.
  7. Distinguish between:
    • SSBs, Helicase, RNA primase, sliding clamp, RNAse (exonuclease), ligase, DNA polymerase
    • 5’ end and 3’ end of DNA
    • Leading strand and lagging strand
  8. Hypothesize what would happen if: (Teacher note:  REALLY emphasize this step to ensure that students truly understand DNA replication and how exact yet fragile the process is. A further task you might add is for students to develop a story, a poster, a video to explain just how intricate the process of DAN replication is and how exact it is and how just one minor change ( a single bases substitution) can cause DNA replication to be done incorrectly and the results if that in terms of protein synthesis.
    • Helicase did not work correctly
    • The DNA polymerase added the incorrect nucleotide
    • Ligase appeared before the strand was completed
    • Only one replication fork opened
    • SSBs were malformed

Closure question/activity- Have students compare DNA replication to one of the following: ( or they could come up with their own example)

  • Knitting a scarf from a template
  • Sewing a dress from a template
  • Building a table from a template
  • Building a model car or airplane from a template

Part 2- Using a variety of craft items (different color yarn or pipe cleaners, buttons, beads, etc.) or types of candy (different color Twizzlers, licorice, mints, etc.), create a model of DNA replication. Include the proteins required, Okazaki fragments and label the 5’ & 3’ ends and the replication fork. Use the model to explain to classmates the steps of DNA replication.

Stage 3: Evaluate

Part 1 - Check for correct answers

Part 8 Answers:

  • If helicase did not work properly several things could happen- DNA replication may never start or if it did, the entire strand might not be copied.
  • If The DNA polymerase added the incorrect nucleotide- an incorrect amino acid may be coded for during protein synthesis IF that piece of the DNA were part of a gene that was expressed by the cell was in.
  • If Ligase appeared before the strand was completed, the fragments that were complete would be put together as they were- before they were checked for mistakes
  • If only 1 replication fork opened, the entire strand of DNA would probably never be fully replicate because it would take too long and the enzymes needed would not be made for that length of time.
  • If the SSBs were malformed-the 2 strands would reattach to each other and replication could not occur.

Part 2 - Develop a rubric using a 4-point scale and include the following:

  • Model is easy to read
  • Model has all of the needed proteins 
  • The 5’ and 3’ ends are labeled
  • Okazaki fragments are aligned in the correct direction
  • Leading and lagging strands have the correct orientation
  • Correct use of model in explaining DNA replication
  • Citing of sources on model

Teacher Notes: Other materials may be used to make the model. Allow students the opportunity to come up with their own materials or give suggestions. Some students will need more guidance on the creativity aspect of this task. If you have insect issues, it would be better to not use candy or to store the model in a refrigerator!