Fun Approach to Teaching DNA Structure

Teaching AP Biology students has many challenges, one of them being that by the time my typical student reaches me they are 3 years removed form freshman biology. As much as they may tell you that they already know something, or “We learned this freshman year”, that does not always translate to “we REMEMBER this from freshman year”. Finding new and fun ways to reintroduce concepts to these students is a challenge that I enjoy.

I have the luxury of having a class set of the 3-D Molecular Designs “DNA Discovery Kit” models. This allows me to have each lab group (4-5 students) use their own kit in this activity.

First, I give the groups each a kit and tell them…well, very little.

I say:

Each group gets one “puzzle” and your challenge is to be the first group to successfully put it together. You must use every piece, and it must be free standing on the provided stand.

Then they begin. Now, I don’t even tell them that it is a model of DNA. Most of them figure that out (especially since it says “DNA model” on the box the model comes in) but knowing that it is DNA does not always translate to being able to quickly assemble the model. Students quickly figure out that they do not know the structure of DNA as well as they thought they did since the “already learned this freshman year”.

Many groups start by just fidgeting with pieces to see how they fit, nitrogen bases get paired up pretty quickly and then we hit some snags and the real learning starts to happen as they begin to problem solve. At this point, many groups will attempt various strategies to get the pieces on the stand. this helps them start to figure out how the components of the nucleotides fit together.

The most successful groups will put together full layers first (two full complimentary nucleotides) and then assemble them on the model. At this point they start to make comments about how each side seems to be pointed in a different direction! The groups that figure it out will then start to push through and their models come together quickly.

I will make sure the first group knows that they “won the race” and sometimes have a prize. Then I will begin to give a few suggestions or tips to the struggling groups to get them rolling.

New thing I did this year:

After everyone is done, I had them all look at their model with a piece of paper and pencil and BY THEMSELVES write down 8 characteristics of DNA that their model shows. This gets challenging once they get to 6 or 7. Next, they work in their groups to create a master list of 10 characteristics. Third, I have them infer a purpose for each characteristic. Finally, I will have the group choose what they feel is the most important characteristic and then share that with the class. This is a good opportunity to have a more guided discussion with the class about the characteristics of DNA and the reasons or purposes for these characteristics.

In my experience, this is an activity that the students seem to enjoy AND students do tend to reference the model in subsequent class periods as they work further through our molecular genetics unit and evidence from student assessments supports that this at least has not discouraged student understanding.

This year, after the activity I had a student very excitedly ask if they could put ALL them models together into one BIG strand. YES, of course we can do that! It …sort of worked. (Pictured at the top)

2020 Ecosystems of Kansas Summer Institute

Several universities across this great state are working together on a massive interdisciplinary project (MAPS – Microbiomes of Aquatic, Plant and Soil Systems). As part of this project, they are holding annual Summer Institutes for teachers interested in the ecosystems of Kansas. This summer is the third edition, being held 8-12 June 2020 at the University of Kansas Field Station. Participants are given travel allowances and a stipend, and anyone with a commute >1 hour driving time from Lawrence will be provided with lodging.

If you are interested in applying, click here.

If you have any questions, contact one of the project leaders, Dr. Peggy Schultz (

KABT Members Drew Ising, Michael Ralph, Marylee Ramsay, Andrew Davis and Bill Welch were participants or organizers for the first summer institute and can also help.

Midwest Regional 3D Symposium K12 Poster Session

An example of what a student poster session

Exciting New Opportunity for K12 Students – The Midwest Regional 3D Symposium has a call out for K12 students and their instructors to submit abstracts for projects that they have completed using 3D technologies! This is the 3rd year for the symposium and first time they’ve had this opportunity for a student poster session. The symposium is being held at Children’s Mercy Park the home of Sporting KC on Friday, June 7. The deadline for abstract submission is this Friday, May 10 at 11:59 pm CST.

You or your students need to be committed to having posters hung between 8-10:00 am and your students would need to be present for presenting their work to judges between 11:50 am and 1:30 pm. There are prizes to be won!

See the following pdf documents for more information on the symposium and the poster session and submission guidelines.

Material Science and Ecological Impact Using 3D Printing Materials

I haven’t exactly been subtle about how sweet 3D print can be…

The various options I’ve seen and imagined have usually focused on the engineering aspects of making. In biology classrooms, I can do a better job of building maker experiences with rich biological connections. Some community conversations have led me to sharing this idea for a project that marries 3D printing and biology is an interesting way.

h/t Drew, Jessica, and Shannon. Also, Topeka Public Schools STEM teachers for a great conversation while I was considering this article – your work impacted this post.


This project could hit lots of standards, but these are the few I had in mind when I wrote this:

Our driving question is important, and is going to mean different things to different people:

“What plastic should we use when 3D printing?”

I would ask the students to begin operationalizing what that question means to them. There are probably going to be two themes in the answers:

  1. What printing materials create the best print products – probably defined by strength.
  2. What printing materials have the fewest negative impacts – probably defined by plastic waste consequences.

I will proceed assuming the first question is the initial focus. If that’s the case, I wouldn’t force any consideration of the second question… it will give us a fun payoff later.

Phase 1: Best Print Products

Students can be given time to create a procedure for stress testing parts printed with different plastics.

What’s important throughout this whole testing process is that you ensure students save every print they make. Broken parts, failed prints, unused replicates… everything they print, they keep!

Phase 2: Matter Cycling

After students complete their analysis of strength, they can return to their driving question. Do they have an answer? If they say ‘strongest is best’, then we can let the conversation move on… to clean-up. What do we do with all this PLA and ABS plastic?

If a particular plastic is best, then we can ask them to think about scale. What happens when everyone starts using it? A big draw for PLA is that it’s not petroleum-based (which is good). The issue still remains of disposal. PLA is compostable, and ABS is recyclable… right?

Students can then read this article from – “What They Don’t Tell You About 3D Printing PLA”. Despite the title, it lays out a good description of what PLA production and disposal looks like. What does it mean for PLA to only be compostable in “industrial settings”? This article from 3D Printing Industry “Is Recycling PLA Really Better Than Composting” describes the various disposal methods of PLA.

This leads into an opportunity for students to learn about matter cycling and home composting. Ideally, they’d create their own compost piles. They can measure moisture and temperature… lots of great science in a compost project.

Phase 3: Solve a Problem

Now that students have some experience with composting and 3D printing plastic, it’s time for them to solve a problem they themselves have made (all their leftover prints)! The students can design their own methods for adding their PLA printed parts to their compost piles. Here are some resources to help:

  • Students can compare the impact of the PLA/PCL blending methods on their originally considered model properties with this peer-reviewed paper

Students could implement a method for adding their plastic to the compost piles, and then collect data for the next month or so. Class could shift focus to other topics while students continue monitoring their projects. The extended time frame could provide the students an opportunity to present the results of a major project around the end of a semester.

These are just some rough ideas I had when I came across the first article. There are basically three steps, and you could approach each in lots of different ways:

  1. Print.
  2. Compost.
  3. Design.

What do you think? Anyone want to try it? I’d love to help/consult with someone who wants to give it a shot.

In My Classroom: POOP LAB! (AKA Fecal Floats/intestinal parasite lab)

A lab favorite in my classroom is the Poop Lab. I teach a Veterinary Medicine course for high school juniors and seniors (life science credit). Parasitology is one of the class foci (is it because I LOVE the gross factor? Probably). If you cover parasites, zoology or even zoonotic diseases, this lab is a must do! YOU DO NOT NEED A CENTRIFUGE to do this lab. Alternative instructions are written on the student lab.

Goal of the lab:  
Perform a fecal float analysis with sample from a  family pet.  Determine if that pet has possible intestinal parasites.

Rationale: Determining if the students’ own pet has a parasite is extremely  engaging (or the neighbor’s pet).  Plus, it’s a darn good microscopy 
exercise on identifying what is significant or not (hair or air bubble).

Homework the night before: I send students home with a disposable fecal collection chamber (1). If you don’t have those, a Ziploc or other small disposable container will suffice (the thicker the better stink barrier it will be). I also give them the option of grabbing a set of exam gloves in case they are horrified by the thought of poo grazing their hand. Students are instructed to collect 2-5 cc of FRESH ANIMAL poo from their pet at home (or ask a neighbor for use of their yard/litter box/etc.). No human poo accepted. ANY pet will work. Iguana, dog, chicken, horse, cat, goat, hamster, chinchilla, etc.

Such a memorable lab…

I’ve usually emailed home to give the parents a heads up that bringing an ANIMAL poop sample to school is legit (no worries about stuffing it someone else’s locker as a prank). FRESH IS BEST so collection morning of the lab preferred, but most animals don’t poop on command. If they have an evening pooping animal, it’s OK to collect the night before, but should be refrigerated overnight (um, this is again where a parental heads up comes in handy – probably won’t want container of poop in the family fridge). If poop is banned from the kitchen, a lunch box with freezy pack. If they use ice to keep it cool, make sure the water doesn’t leak into the poo container. That is a lunch box sludge that is best avoided.

Lab Day: If this is not your students’ first time using a microscope, this lab can be completed in a 45 minute session, including cleanup. This is possible because I prefer to maximize the use of disposable items. After the first student spills a test tube of sugared poo slurry and you see how difficult it is to clean up the sticky mess, you’ll thank me for that little tidbit of wisdom. Try asking your local Sonic, etc. for a donation of a box of smoothie straws (AKA disposable scoopulas) to mentally scar students’ future enjoyment of smoothies following this lab.

Here’s the one-page handout of instructions that I give each student:

Who wouldn’t be all smiles after retrieving the poo slurry from the centrifuge?

I built tips into the instructions, so give it a good read before trying with students. You will need a comparison chart [(2) or extension activity described below BEFORE this lab] so that if students find something that looks like a parasitic egg (4), they can try to identify which parasite might be infesting Fluffy’s intestines.
You will need to order or mix up a sugar solution ahead of time (3). Wards has a “Fecal Slide Analysis Activity” which boils down to this same lab. I wouldn’t spend the money on it (although I did the first year), unless you like the handy dandy teacher manual (which does have some interesting fun facts – but that’s all I like about it).

How it works:  The parasite eggs (4)  are less dense than the solution.  After centrifuging (or allowing to sit  for a length of time), the eggs float to the top of the tube.  They bind to  the coverslip, allowing us to see the eggs on the scope.  The parasitic  infection can be determined based on the shape/appearance of the eggs on the slide.

IF there is anything suspect, use an identification chart (2) or a scientific based website to try to match the microscope image with known parasite pictures. See additional activity ideas below. Check out this website: I like that towards the bottom, they also identify other items which might be seen on the slides and are no cause for alarm (normal bacterial flora, hairs, air bubbles).

My students have seen green blobs that look like stacked bricks. It’s a hoot for them to try to guess what network type of parasite that might be, only to finally draw the connection between plant cells from Bio I and, “oh yeah, my dog ate grass.”

Strongyles from horse. Image from my class, fall 2018. Note that this slide sat on the scope a little too long so the sugar solution is starting to get sticky under the coverslip. Too much longer and it would have been crystalized.

Three swine whipworm eggs can be seen, approximately diagonal from upper right to lower left. Image from my class, fall 2016. This was considered a low parasitic load and we did not treat the pig sounder at that time.

Note about livestock: It is actually considered normal for a livestock animal to have some parasitic load. This keeps the immune system fighting the parasites instead of treating again and again to the point they become resistant. Instead of a fecal float (like this lab) for diagnosis, a count is performed after isolating possible eggs. A cell count slide is used (sounds like a hemocytometer to me). If 1 cc of fecal matter yields over a certain threshold for that parasite in that animal, then treatment is administered. Don’t ask me the threshold – if you come across any more info about this, please add to the comment section below. Fall 2018, my students found Strongyles (a horse nemotode) in the poo I brought in from one of my horses. I showed the picture to my veterinarian. Although we didn’t quantify, she felt it was probably a low parastitic load and would naturally be kept at bay. I rotate through a different dewormer for my horses every spring and fall. Horse strongyles can’t be passed to my happily horse poop eating hound dogs, so they continue to be clear every time my class looks at their poop.

What to do if evidence of parasite IS found in a pet:
Instruct the student not to panic. Have the student take a photo of the microscope image. It is recommended that he/she share the information with the parent to possibility be passed along to the family veterinarian. The vet while likely ask for a fecal sample or to bring the pet to the clinic for a fresh sample to be taken (via tiny spoon inserted into the anus – very fresh). Some veterinarians might do a version of an ELISA to confirm various parasites. After doing this 10 semesters in our suburban school setting, I have only had one pet fecal sample come out positive (Coccidia). That was a sample collected the morning of class from an abandoned poo pile in the student’s yard. Honestly, the HUNT for parasitic evidence is fun – you really don’t want a positive result. That means the pet *likely* has a parasite.

Coaxing 2-5 cc of horse fecal matter into the collection tube.

Extensions / additional activities pre or post lab:

References to above

If you want the “real thing,” these are two types of fecal collection chambers on the market.

(1) – Ordering info for collection chambers – the “official” fecal collection chambers aren’t needed. A disposable conical lab tube (with lid) would be fine. However, if you want the “real thing,”

(2) – Identification chart: You might be able to obtain some charts through your local veterinarian OR make your students create a chart as a pre-lab (described in extension activities). I have found that Pinterest has several charts, found through a quick Google search (make sure you’re looking at companion animals, not just goat parasites):

(3) – Ordering info for Sheather’s Fecal Float (sugar) Solution – you can mix this up yourself with sucrose and dWater. The exact specific gravity should be 1.27. The solution is described in Dr. Dryden’s article below (Magnesium Sulfate solution can be used instead of sugar, also described in the article). Alternatively, you can order the solution pre-made.

  • Dryden MW, Payne PA, Ridley R, et al. Comparison of common fecal flotation techniques for the recovery of parasite eggs and oocysts. Vet Ther2005;6(1):15-28.

4) – “Eggs” are used generally in this article. Depending on the parasite, students may actually be looking at/for the actual protozoa (Giardia trophozoite), the egg (tapeworm or hookworm oocyte) or cyst (Giardia cyst – tenacious temperature tolerant oocyte manifestation).

(5) – Possible companion animal parasites include: Alaria (intestional flke), Spirometra (taepworm), Paragonimus kellicotti (lung fluke), Platynosomum fastosum (liver fluke), Dipylidium canium (flea tapeworm), Taenia species (tapeworm), Capillaria aerophila (lungworm), Trichuris vulpis (whipworm), Uncinaria stenocephala (hookworm), Ancylostomas species (hookworm), Physaloptera species (stomach worm), Toxascaris lonina (round worm), Toxocara cati (roundworm), Toxocara canis (round worm), Baylisascaris species (racoon roundworm), Strongyloides larvae (threadworm), Giardia trohphozoite, Giardia cyst, Isospara species (Coccidia), or Toxoplasma gondii.

Additional resources: