# DNA Replication

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This lesson is designed to take place in a 100 level Biology classroom but could be easily adapted for high school level students.

As a TA at University, I noticed that students were struggling with DNA replication. They weren't quite grasping how often errors occur and that even with DNA Polymerase correcting them errors could still be missed.

So I decided on changing up the lab experiment to reflect the issue they were struggling with. So I created a 3D model of DNA using tinkercad!

I wanted them to experience what it was like to go through the process of DNA. Each student was partnered up with another student. Each member was given time to look at the printed strand of DNA (10-30 seconds). One student looked at one half of the strand, and the second student looked at the other half.

The students were then taught how to make DNA using tinkercad. Each student went through and built their own strand of DNA based on the notes that they had taken during class.

Once they finished this up, they would switch halves of DNA with their partners, and from their own notes would have to go through and try to fix any errors in the DNA that they found.

Once that step was completed the pairs would combine their halves of DNA with their partner, and go through checking for errors.

After this, they saw how easy it would be for errors to slip right past.

For this tutorial I will show you how to make a strand of DNA, so that you can do this activity in your class.

### Supplies:

• Computers
• Stopwatch
• Pencils and paper

### Teacher Notes

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## Step 1: Creating the Base

Place a cylinder on the grid, stretch it, so that it is 50 wide, 50 long and 4 high.

## Step 2: Creating the Name Plaque

Place a wedge on the grid, shrink it, so that it is 20 long, 11 wide, 10 tall. Raise it, so that it is 4 off the ground and place it onto the platform. Next, highlight the whole area and click group.

## Step 3: Placing Text on the Plaque

Place text on the grid, and type in DNA. Make the text 15 long, 11 wide, and 3 tall.

Once the text is properly aligned, highlight the entire thing and group it.

Next, highlight it again and hit color, tick the box that says multicolored.

## Step 4: Building the Rungs.

1. Place a sphere onto the grid, make it 3x3x3. Duplicate it, so that you have four spheres.
2. Take two balls, and place them off to the side, so that they are an entire grid space away from each other. Align them best as possible. Now highlight them, click the align button in the upper right corner, once they are aligned group them.
3. Next, take a cylinder, lay it on its side. Make it 2 wide, and 2 high, with a length of 3. Color it red (Red will stand for Thymine) Now duplicate it, and turn it green (green will stand for Adenine). Now place the cylinders, so that the circular part touches and group it. Click on the grouped object, and select color. Click the box that says multicolored.
4. To complete the first set, place the conjoined cylinder in between the set of spheres. Expand the cylinders as needed, so that it fits in between the set of aligned spheres. Highlight and group it together.
5. Repeat these steps, but make the cylinders blue and yellow. Yellow will stand for Guanine, and blue will stand for Cytosine.

Next, decide how many ‘bars’ tall you want your DNA to be, and replicate the set of bars accordingly.

## Step 5: Stacking the DNA

Place a cylinder on the grid standing upwards. Make the circular part 2.5 by 2.5 with a height of four. Place the cylinder on one of the spheres, and raise it, so that it sticks out of the ball. Duplicate the cylinder and repeat for the opposite sphere, now group the object.

## Step 6: Completing Your DNA

Place the next set of bars on top of it raising it slightly. Angle it between 5 and 7 degrees. Repeat until DNA is at the desired height.

Repeat this until DNA is an acceptable length.

Towards the top I did a deconstruction to show what the DNA would look in different stages. So

## Step 7: Activity

Give each student the instructions on how to build DNA.

Take your model of DNA and place it in a second room. Split your class into two groups, and partner them up with a member of the opposite group Allow Group # 1 to look at the DNA for a time range of 10-30 seconds, during this time students should take notes as to the structure of the DNA. Allow them to go back to the classroom, and start on their DNA. Allow Group #2 the same amount of time to look at their half of DNA and then have them start building. Once the building of DNA is complete. Allow students to look at their teammate's DNA, and fix any errors in their partner's DNA using their own notes. (This will allow for errors to be fixed and made by each person in their attempt to fix the DNA.) Now have the students combine their DNA with each other, and by comparing which bases should be with each other have them note how many errors they made. Have them take a percent error, and have them place it on the board, so that students can compare percent error.

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