Sickle Cell Anemia Investigation: Day 4

Today began with a video by John Perry’s series “Stated Clearly” titled “What is a gene?”

Next, students wrote down the learning objective. A protein’s shape determines its function, and the shape occurs due to the sequence of amino acids coded by DNA. I explained that a truck has a specific shape that helps it to do its function of hauling things and a ferrari has a different shape that helps it to do its function of going fast. Proteins too have specific shapes to help them do their own function.

It is a difficult abstraction for students to take to look at a protein model and think that these microscopic things actually have a function.

Though these models of look interesting to a student to assume that one has a function is very difficult. The one on the left BCR-ABL Fusion Protein stimulates cellular division and the right Aquaporin allows water to pass through membranes. This form function can be a stonewall for a 14 year old due to the level of abstraction involved.

In order to help students realize how these proteins function can work I use minitoobers. (*this is not my own original idea.) I tell students that they have to fold their protein using beta pleated sheets a.k.a. zigzags or alpha helicies a.k.a. loops into a shape that can pick up a molecule and transfer it from one partner to the next. I give them 3 minutes to fold their toober into a shape that can make the transfer and then let them show the rest of the class their solution.

Oven mitten design
The trade off!
The Eagle has landed…

Students fold their proteins into many different shapes to perform the function of moving a protein.

A hockey stick solution

I can then show them It turns out these protein things can have many shapes! You can show the kids these proteins too from the Protein Data Bank.

Now we turn our attention to how the sequence of DNA effects the shape of a protein. I am using kits that we purchased from 3dmolecular designs. But, colored push pins will work too. ( I think Drew Ising did a post about this in the past).

I start this by having the students place a positive amino acid (blue) on one end of their mini-toobers and a negative amino acid on the other end.
Next, students evenly space just four hydrophobic amino acids (labeled yellow here) across the mini toober.
Finally, they place four hydrophilic amino acids across the mini toober.

At this point I pause the class and open a concord consortium interactive player on my smartboard.

I ask student to predict how the positive and negative amino acids will behave and how the hydrophobic and hydrophilic amino acids will behave. They can all get it.
Beautiful! Opposites attract! I love this! Thank you to whoever created this.

Now it is the students chance to fold the protein into a shape where the positive and negative amino acids on the ends of their toober attract to one another and the hydrophobic amino acids fold in.

This looks about right?!

At this point I grab one of the students folded protein and I substitute one positive amino acid for a negative amino acid. They can see that it will unravel their protein. Now I try to hit home the reason that a mutation in DNA can cause an impact in an organism.

I had a few Hemoglobin molecules printed off for my classroom. I found the STL files on Thingverse. So, now the kids can see the shape of the protein is different. When only one amino acid is changed.

It turns out that DNA causes a visible change in proteins.