Washington State University
Washington State University Colleges of Veterinary Medicine and Education
Department of Veterinary Microbiology and Pathology
Pullman, WA 99164-7040
Dr. Inge S. Eriks, Director
Tel: (509) 335-6071
Fax: (509) 335-8529
Summer Workshop 1997
Microbes in Our Schools: Integrating Microbiology into an Elementary Curriculum
Instructors: Inge Eriks, DVM, PhD (e-mail: firstname.lastname@example.org)
Rena Mincks, First grade Teacher (e-mail: email@example.com)
Julie Clark, Sixth Grade Teacher (e-mail: firstname.lastname@example.org)
In the summer of 1997, we taught a summer workshop designed to introduce elementary school teachers to fundamentals of microbiology and how they could incorporate microbiology into their existing curricula. As a part of this workshop, we developed a website that has an overview of the workshop curriculum as well as numerous links that could be of use to teachers for many different age groups. The website from the workshop is at:
What follows are some of the experiments/activities that we did last
summer that I feel were particularly worthwhile for the teachers.
Please keep in mind that these activities were aimed at elementary school
children, and that the teachers themselves had minimal scientific background
in many cases. We therefore prefaced many of the experiments and
activities with a lecture/discussion format to introduce the teachers to
the topics to be discussed.
I. Introduction to microbiology: What are bugs?
A. Introductory Discussion/Lecture: I have successfully
introduced this material in a discussion/question-answer format for groups
of students from kindergarten through fifth grade
1. What are Viruses:
How big are they?
What kind of microscope is needed?
Are viruses alive?
What constitutes life?
What are some common viral diseases? (AIDS, common cold, flu, rabies)
2. What are bacteria?
How big are they?
-You can compare sizes to viruses by using ratios
-Talking about bacterial and viral sizes also brings up the mathematical concept of very small numbers, which teachers can present to classes. Teachers can also talk about concepts related to powers of ten.
What are some common bacterial diseases? (Strep throat, pneumonia, ulcers, pimples)
What are some common beneficial uses of bacteria? (Yoghurt, cheese,
certain medicines, decomposition, digestion etc. Also, much of molecular
biological technique, which has helped to vastly decrease the need for
animal experimentation, relies on bacteria)
3. Yeasts/Fungi: Size-compare to viruses and bacteria Examples: mushrooms and mold
Composed of more than one cell
Some common diseases: Ringworm, Athletes foot, thrush
Some common beneficial uses of yeasts/fungi: We eat them! (i.e. mushrooms); yeast for bread baking; fermentation, including many foods such as soy sauce and beer; certain medicines, and again, molecular biology.
Based on the size of bacteria vs. the size of a pencil tip (or any other
object of your choosing), have students figure out how many bacteria would
fit onto the tip of their pencil? How many viruses?
"The Biology Place" on the WWW has some very nice interactive sites including one related to sizes and scales. You do need to pay for this site, but teachers can get a free trial membership to see how they like it. The address for this site is: http://www.biology.com/
Another useful reference that is extremely helpful for introducing large numbers is the book "How Much is a Million" by David Schwartz.
You can bring in numerous different mathematical concepts by talking about bacterial replication. First, explain to the kids that bacteria multiply by dividing themselves, so that one bacteria becomes two. Now you can have the kids start to figure out what would come next - i.e. two bacteria would divide into four, four into eight etc. Pretty soon they'll be dealing with some very big numbers. With young kids (kindergarten age), you can draw out what's happening and get the kids to count along. With first and second graders, you can make it into an addition problem. With slightly older kids, you can talk about multiplication by two. Finally, you can use this example to introduce kids to the concept of powers (i.e. NO rounds of replication is 20 = 1; ONE round of replication is 21 = 2 and so on). This is a great way to put math into a practical context that kids can understand - they'll respond by getting quite excited about it!
a. Children can design viruses, using everyday materials that they bring in from home. These include pipe cleaners, toilet paper and paper towel rolls, plastic bottles and containers of various sizes, beads, etc. etc.
Probably one of the easiest (and most fun!) viruses to design is the bacteriophage T4 virus. However, many other types of viruses can be built. There are many places to find pictures of virus structures. For younger students, teachers may wish to have pictures available, but older students (and really, even the younger ones can do this) can look for good pictures on the Web. One of the best places I've seen to access all sorts of different types of pictures (EM, diagram etc) is the following website:
This site has a resource on it entitled "Big Picture Book of Viruses"
that is really incredible.
By designing the virus, students learn about the parts of a virus: the envelope, the capsid, and the viral nucleic acid. You can have students design different types of viruses in small groups, then have each group explain their viral structure to the rest of the class. Initially, the structures may not be very detailed, but as students gain more understanding of viral structural details, they may add different types of transmembrane proteins; outer membrane proteins; they can also color code their nucleic acid inside the virus to correspond to the part of the virus it is responsible for encoding. To reinforce an understanding of what a virus consists of, older groups of students can take their final construction and explain it to classes of younger students.
b. Another hands-on activity that we did essentially involved putting
on a play to show how viral infection of a cell occurs. Everybody
except for one person held hands to form a large circle. This comprised
the "cell". The one leftover person was the "virus", and wore a cloak
to signify the viral "coat". As the virus entered the cell, it left
behind the cloak, to show viral uncoating. Following entry into the
cell, the virus then took over the cellular machinery. It started
using the cell to replicate itself. We signified this by having the
"virus" take people from the "cell" into the center, where they now became
new viruses. As more and more viruses were "produced", the cell became
more and more crowded, until eventually it "burst" open, demonstrating
cell lysis. This role-play really helped the teachers understand
at least some of the aspects of viral replication. If you wanted
to make it more sophisticated, you could alter the scenario to demonstrate
whatever type of viral replication you wish. With older students,
you could have them make up the scenario for the play based on their readings
on viral replication.
3. Other Resources
We talked quite a bit about the advantages and disadvantages of using microscopes to look at bacteria, yeasts, protozoa etc. Some major disadvantages, particularly for young children are the costs involved in purchasing the scopes; the difficulty of getting around to help everyone; and in particular the frustration of trying to focus - which is extremely hard for younger kids. There are some alternatives - the best is probably the "Flex-Cam" which I believe is from Carolina Biologicals. It's extremely expensive, though. If teachers want to explore some other alternatives, there are some excellent Web sites available. These include:
The website for the Microscopy Society of America: http://www.msa.microscopy.com/
They also have several specific sites that might be of particular use to teachers:
Another site, which has directions for making a homemade microscope, is:
II. Health and Safety
We felt this was a very valuable topic, because health and safety must
be taught at all age levels, and because people have numerous misconceptions
about both health and safety, as they relate to microbiology.
In relation to health, we began by having a group discussion focusing on current topics in the news. This could easily be done in a class setting by asking students to bring in newspaper or magazine clippings related to human health. Topics could include a discussion on HIV and AIDS; Ebola virus and its potential spread; as well as many other diseases. However, because people tend to focus on the negative aspects of microbes, we also wanted to emphasize positive topics related to microbiology. These included the new uses of bacteria to decompose substances such as oil and other environmental hazards. We also talked about our own normal body flora and how important this is in disease prevention. We discussed how microbes from whales are being identified that can detoxify certain harmful pollutants, as well as how bacteria from hot springs are being used to identify thermotolerant enzymes.
Interestingly, as a result of these discussions, teachers enthusiastically brought in articles and clippings from newspapers and magazines every day of the workshop!
We also had a discussion about foods and food safety. Again, here we wanted to separate out the good and bad aspects of microbiology. To tie food safety to literature, we read some passages from Lewis Sinclair's "The Jungle". (Similarly, you could tie health issues to literature, with books such as "The Hot Zone"). We then discussed current issues involving food safety. These included the recent upsurge of E. coli O157:H7 and Salmonella DT104 outbreaks. We also discussed beneficial aspects of microbes in foods, including their use in cheese and yoghurt production, sourdough production etc. This led to a discussion on food preservation techniques, including pickling, canning, pasteurization, irradiation etc. We had a lecturer from the Department of Food Sciences come in to talk about the history of food preservation as well as current issues, including food irradiation, cooking, food handling at home etc.
1. Hand-washing. I have used this activity very successfully in teaching children of many different age levels about the principles of proper hand washing. In fact, we use this experiment in our veterinary curriculum. This was one of the ONLY activities that utilized agar plates during the entire, week-long workshop. However, it is a powerful learning tool for teaching the importance of PROPER TECHNIQUE for hand washing.
There are several companies available for teachers to buy agar. However, if teachers can work with local hospitals or laboratories they can save money. Often labs will discard plates that are outdated, even though they're still perfectly ok to use. Labs may be willing to donate these items to the schools.
It is important to emphasize proper safety when dealing with agar plates. I never allow the students to open the plates after they've grown things up on them. With younger students, I generally tape the plates, to be sure they don't open them. After examining the plates, there are several ways to dispose of them. Obviously the best is to tape them up securely, double bag them, and take them somewhere for autoclaving. Local hospitals or clinics may be willing to help out with this. Alternatively, you can use 75% ethanol - flood the surface of each plate with it, then cover and tape plates shut, and let them sit a minimum of 24 hrs.
You can run this as a hypothesis-directed experiment - it's very effective in demonstrating what is meant by this concept. Encourage the kids to keep a science "notebook" in which they record the experiment from start to finish. For young kids, it may be entirely pictorial; you can get more sophisticated depending on the age group of the kids.
1] Hypothesis: Formulating a hypothesis is simply asking a question, and thinking about what the answer might be. In this case the question might be: Does hand washing reduce the number of bacteria on my hands? However, this may not be the only question you're asking. You may also ask: What effect does the type of soap, or the length of hand washing have on the number of bacteria on my hand? A discussion on the types of questions being asked will help to focus kids on WHY they're doing the experiment in the first place.
An important aspect of formulating hypotheses is that we DON'T KNOW the answers. Thus, if an experiment turns out DIFFERENT from what we might have expected, it DOES NOT mean we were wrong! It simply means that we've learned something new that we didn't know before. It's extremely important that kids understand this distinction, because if they think they were wrong, they'll be quite disappointed in their results; if they realize that they've DISCOVERED something they didn't know before, it will make them all the more excited about the results!
2] Materials and methods: Have the kids come up with a list of what materials they think they might need, and how they would run the experiment. You can discuss the advantages and disadvantages of different methods as a group.
Here is the method I've used in the past:
Students should not have recently washed their hands. In fact,
coming in from recess etc. is a good time to do this. Each student
gets one blood agar plate (you can use TSA or other plates, but I think
blood agar works best). The plate is divided in half by drawing a
line on the outside of the plate (on the bottom). Additionally the student
must label the plate with their name and date. The student then takes one
finger and gently rubs it down one side of the plate.
Students then wash their hands. This can be done in a variety of ways- we used different types of soap (bactericidal and "regular") as well as having different people wash their hands for different lengths of time. Another variable is the amount of time spent drying the hands - this turns out to be extremely important.
After washing and drying their hands, students rubbed the SAME finger down the other side of the plate.
Plates are turned upside down, to prevent condensation, and incubated overnight. Obviously, an actual incubator works best. However, most teachers won't have access to this. Some alternatives are: 1] An incubator for hatching chicks works quite well and is very inexpensive. Many teachers have access to these. 2] I have actually incubated plates in my oven overnight. You have to be careful - I heat the oven up at the lowest setting possible, and then turn it off - it will maintain its warmth for long enough to grow up bacteria. After taking out the plates, I then turn the oven on to @3500F for about 10 min. Obviously this is NOT something you would do in the school lunchroom ovens!! 3] You can have the kids MAKE an incubator using some type of inflammable box, a lightbulb or heat lamp, and a thermometer. If you want to get fancy about it, you can hook the lamp up to the thermometer, so that it goes off when the temperature gets to the proper setting. 4] If you don't have access to any type of incubator, you can keep the plates in a warm room overnight, or preferably 2 days. Bacteria will grow at room temp, it's just not really optimal, and it may take longer.
3] Results: When the students get their plates back, they are asked to look at and compare several different parameters. With younger children, drawing pictures of what they see is very helpful. You can ask older children to either draw pictures, write down their observations, or preferably do both.
a] Have the kids look at the total numbers of bacterial colonies on both sides of the plate. They don't necessarily have to count them; they can rank them - you can even have them decide together on a ranking system ahead of time. They should then compare the total numbers of bacteria on both sides of the plate, and decide which one has more.
As a side note, this is a great time to bring in the idea of bacterial replication (see math section above). I always ask the kids "Why couldn't we see anything on the plate yesterday, and now there are these big colonies?" You can then try to get the kids to come up with a comparison of other situations where we might not see only one of something, but if you put enough of them together, they become easy to see. My favorite is to compare the individual bacteria to a grain of sand on a beach. From an airplane, you can't see one grain, but you can certainly see the whole beach!
b] Students should also examine different colony morphologies. I always ask them what properties they can use to distinguish different colony types - color and size are obvious ones, but shape is also important. Also, they can see whether the colony looks shiny, dry, fuzzy etc. If you're using blood agar, you should also point out hemolysis to the kids. I explain to them that some bacteria are able to break down the red blood cells found in the agar and use them for energy - they essentially "eat" the red blood cells. With all ages, it's a good idea to have them draw out the different colony morphologies. It really makes them look harder at each different type.
c] Once students have looked at the different morphologies, they should compare the number of different colony types on both sides of the plate.
4] Conclusions: At this point, I ask the kids to come up with some kind of a conclusion - why do they think they got the results that they did? With older kids, its best to have them write down their individual conclusions before discussing it as a group, because they tend to be heavily influenced by each other. What frequently happens is that there are actually more TOTAL colonies AFTER hand washing than there were before. However, the COLONY TYPES after washing tend to be greatly reduced. Often, there may be only one or two colony types after hand washing. It's very interesting to have the kids brainstorm why they think this happened. There will tend to be more bacteria after hand washing, because the normal flora has been dislodged by the physical activity of washing. Because the hands are likely to still be damp, those bacteria come off the hands quite easily and onto the agar plate. This points out the importance not only of WASHING your hands, but of thoroughly DRYING them as well.
It's also a good idea to discuss with the kids the concept of normal flora. We are all covered with bacteria - they are a normal part of our skin and mucous membranes. You can ask the kids to come up with reasons why the normal flora is important. One important reason is that they fill a niche on the body that helps prevent the potentially harmful bacteria from getting in. They may also produce substances that kill other bacteria - again keeping out the potentially harmful ones.
Other Resources. The American Society for Microbiology recently had a big campaign to promote hand washing ("Operation Clean Hands"), and you can get information, as well as stickers etc. from them. For more information, the website about Operation Clean Hands is:
2. Simulating an epidemic (AIDS or other type of epidemic)
This is a great activity to drive home the relative ease with which an epidemic can get started. For middle school kids (or high school even) who are learning about sexually transmitted diseases, and HIV in particular, this activity also gets across quite nicely the importance AND the incredible benefits of preventative measures. I will present the activity as it relates to transmission of HIV, but you could certainly modify it to many other diseases as well.
To really get the kids' interests up, it may be best not to say too much about what they are doing and why they're doing it ahead of time. Give each student a card. On the card will be specific directions, which will be different for each student. The cards tell them to shake hands with one or more people - you can either specify the people, or you can have them write down each individual that they shook hands with. Each "handshake" will represent an encounter (with HIV it will be a sexual encounter). Some students will be told to shake hands with only one other person. To simulate the use of condoms, you can have some students put on rubber gloves before they begin shaking hands. If you really want to get detailed, you could even have one of the gloves have a small hole in it!! To simulate abstinence, some of the students won't shake hands with anyone else. One student will have a card that has a red dot on it. They will be the initial "source" of the disease. They should obviously shake hands with a number of different people.
After everyone is done, find out how many students shook hands with the initially infected person. Have those students either raise their hands or come to the front of the class. Then ask who shook hands with THOSE students, particularly AFTER they shook hands with the infected source. Keep going until you have identified all the people who were potentially exposed. Keep in mind that if students wore gloves (condoms) they would not be considered exposed UNLESS the glove had a hole in it. It will be quite impressive to most students to see the number of potential exposures that can result from just one infected person. Once you have discussed the results with the students, they may want to know what would happen if some of the variables were changed. You can then repeat the activity using different sets of cards to simulate different types of conditions.
Other Resources: There are MANY different resources available for HIV education. One really good one that we found is entitled: The Science of HIV: A comprehensive HIV Curriculum with Student Activities and an original Video. This curriculum guide is put out by the National Science Teachers Association. It's full of information and doesn't "talk down" to the kids. The video that accompanies it is probably one of the best I've seen - very informative, interesting, scientifically accurate and very up-front. Their web address is:
They have an on-line "science store" that you can get to at this site:
3. Food Safety/Food Production
Bacteria, yeasts and fungi are a very important component of food production and food safety, and it's important for kids to understand that these organisms are beneficial as well as detrimental. In our workshop, we had some very interesting discussions on microorganisms as they relate to food in our culture as compared to other cultures. We actually had a medical anthropologist, who has worked with the Pygmies in Africa for many years, come in and talk about how they preserve food and what their overall view on food hygiene is. Many children don't even realize that things like refrigerators and freezers, that we take for granted, aren't available in many parts of the world. You can have the kids brainstorm alternative methods of food preservation. Methods such as canning, salting, drying and pickling help to vastly reduce the numbers of organisms found in food. You might even talk about irradiation - which was just approved by the USDA. You can explain that this does NOT make foods radioactive!!
You can also talk about how microorganisms are frequently involved in a good way in preserving foods. There are numerous examples, many of which lend themselves quite nicely to hands-on activities.
1. Making yoghurt in class is an activity that is lots of fun for everyone. It's also very easy, cheap, and the results are edible! The easiest way to make yoghurt is to take pasteurized milk and scald, but don't boil it. Let it cool, then add some plain yoghurt from the store (be sure that it has active, live Lactobacillus organisms in it). Put it into a container (a plastic tub or bowl with a lid works very well) and keep it in a warm, preferably moist area overnight. To make this demonstration more scientific, you can put live culture into one container of milk and not into the other and compare the differences the following day. Finally, what I've done with classes is to PROVE that there are live bacteria in the active cultures by taking an agar plate and swabbing some yoghurt onto it. The kids are always very impressed when you grow things out of the food, especially because there will usually only be a single bacterial type.
2. You can also easily make sourdough starter in class. Take some flour, add some water to it to make a relatively thin, pancake consistency. Then leave it out on a shelf for a day WITHOUT covering it. As a control, you can cover one container and not the other. After a day or so, add some more flour and water. The mixture that was left uncovered should start bubbling after a few hours. You can continue to feed it by adding flour and water. To keep it from dying, simply cover it and put it in the refrigerator. Sourdough gets better with aging, so you can take it out once a week and feed it, let it sit out (covered) at room temp overnight, then refrigerate it again. You can then actually USE the sourdough to make bread or pancakes with your kids.
3. There are many other activities that demonstrate the importance of microorganisms in food preparation. These include making cheese, root beer, yeast breads etc. These activities can be aimed at many different age levels, and can be done at different scientific levels. For example, when talking about yeasts with older kids, you can discuss fermentation, fermentation by-products, gas production, etc. You can measure many of these things - gas production can easily be measures by fermenting in a bottle with a balloon tightly attached to the top. Acidity can be measured with pH paper, looking at changes over time. The possibilities are almost endless, and once you get the kids excited about them, chances are they'll want to look at as many possibilities as they can!
III. Functions of the Cell
A bacterium is a unicellular organism and, as such, must have all the different components necessary for survival within that one cell. Thus, in many ways the bacterial cell could be likened to a community. During our workshop, we spent some time identifying the components of a community and finding analogous components within an individual cell. This can easily be done in the classroom and can help children understand the many similarities between our "macro" world and the "micro" world. You can do this at the cellular level, or alternatively, you could compare our bodies to a community. However, because we were talking about microbiology, we focused on the individual cell.
You can begin by having the kids come up with all the different components necessary to make a city/town function smoothly. You might even want to take a field trip downtown to look at some of the different components. These would include:
Road system for connecting places/way for movement to occur
A police department for protection
A sewage system to get rid of wastes
Now you can have the kids research how an individual cell takes care of these different things. For example, the government of the cell would be the nucleus, or in the case of bacteria, the DNA because it is essentially "in charge" of what happens in the rest of the cell. Within individual cells, actin fibers could be seen as connecting the different parts of the cell together. However, as far as overall movement, you could also see flagellae etc. as being important. The cell gets its energy from the mitochondria. The houses could be the proteins, which are put together by the builders, which are the ribosomes. Goods would come into the cell via various pumps and pores in the membrane. The cell would get rid of wastes in a similar manner. The cell might have lysosomes that act as "policemen" as well as receptors on its membrane that would keep track of what's going on outside the cell.
Once the kids have come up with some ideas about the different components of the cell, you could actually turn the classroom into a giant cell. Most likely, the teacher will be the nucleus or DNA. You could make the door into a pore, which allows things to go in and out. The kids themselves could then take on the roles of the different proteins etc. - some could be policemen, some could be mitochondria and provide snacks to the other kids etc.
IV. DNA/RNA and DNA Fingerprinting
Molecular biology is becoming a more integral part of our society every day. If kids are introduced to some of the fundamental concepts of molecular biology early in their schooling, they'll have a much greater understanding and appreciation of what's going on. You can have some great discussions with kids at many different age levels about uses (and potential misuses) of molecular biology in our society. You can encourage them to bring in newspaper or magazine articles. You can discuss the pros and cons of gene therapy; cloning of animals (such as Dolly the sheep); use of DNA fingerprinting in murder cases or paternity suits - the list is endless. With older children you can get into some very interesting discussions. You might even encourage them to conduct a debate about certain issues. In our middle school, each year the advanced English block conducts a series of mock trials. You could have a trial in which DNA fingerprinting represents part of the evidence that must be brought in. The "lawyers" would then have to explain how fingerprinting works to the "jury".
Ultimately, an understanding of much of molecular biology relies on understanding what the function of DNA is. This may seem like an overwhelmingly complex subject. However, when my daughter was in third grade, her teacher asked her to devise a way of explaining some basic concepts to the class. She developed a metaphor that was really better and more understandable than anything I could have come up with. When she got done explaining her metaphor, she had the kids solve a DNA "code" worksheet. By the time they were done with this, the kids really understood the basic concepts of what DNA is and how it works. Her metaphor consisted of pictures along with the following text:
OVERVIEW: The cell is the city of Pullman. The nucleus is the reference section of the Neill Public Library. Genes (DNA) are the reference books kept in the library. The books cannot leave the library; they stay in the nucleus. Proteins (houses) are built of amino acids (bricks) in the cytoplasm (the city). Directions for building houses must be transferred from the library to the rest of the city.
Picture#1: (girl standing at the reference section of the library, pointing to a book called "How to Build a House"). Caption - "DNA is in the nucleus. It is a book called 'How to Build a House'."
Picture#2: (girl sitting at a table copying things out of a book). Caption - "DNA is transcribed to RNA. Because the book (DNA) cannot be taken out of the library, the girl copies the information into notes (mRNA)."
Picture#3: (girl walking out of the library). Caption - "mRNA leaves the nucleus and goes to the cytoplasm. The girl takes her notes and leaves the library."
Picture#4: (girl with papers standing by a partially constructed brick house - individual bricks moving to correct location). Caption - "Ribosomes translate the mRNA and assemble amino acids into a protein. Amino acids are the bricks for the house (the protein)."
Picture#5: (continuation of house under construction). Caption - "Protein in progress....."
Picture#6: (finished house). Caption - "Protein finished. Yea!"
Prior to explaining her analogy, she explained some of the basic principles of DNA to the class. She also introduced them to some of the vocabulary. At this point it was obvious that only a few kids knew what she was talking about. Next, she showed the class the analogy, and explained each picture to the kids. Finally, she had prepared a "coded message" game that consisted of the kids having to transcribe DNA into RNA (the way transcription occurs had been explained to the class), then taking each triplet and finding the one letter amino acid designation. The code game is on the following page. It took the children a while to understand how the code worked, but after showing them one or two amino acids, they quickly got the hang of it. By the end, all the kids seemed to have a good understanding of how DNA works.
CAN YOU FIND THE SECRET MESSAGE HIDDEN IN THE PROTEINS?
DNA C T A T T A C G A T A
T A G G
RNA _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
PROTEIN ___ ___ ___ ___ ___
DNA C C C T C T C T C C G
T T G G
RNA _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
PROTEIN ___ ___ ___ ___ ___
LETTER NAME OF AMINO ACID RNA TRIPLET
A Alanine GCU or GCA
C Cysteine UCU
D Aspartic Acid GAU
E Glutamic Acid GAG
G Glycine GGG
H Histidine CAC
I Isoleucine AUA
K Lysine AAA or AAG
L Leucine CUG
M Methionine AUG
N Asparagine AAU
P Proline CCC
Q Glutamine CAA
R Argenine AGA or AGG
S Serine UCC
T Threonine ACC
V Valine GUU or GUC
W Tryptophan UGG
Y Tyrosine UAU
Finally, a great activity designed to introduce students to the idea of DNA fingerprinting is a group activity called "Who stole the cookies from the cookie jar?". This activity was taken from one done at the Smithsonian Institution National Museum of American History. They have designed numerous activities for their "Hands On Science" program. We first did this activity with kids shortly after the O.J. Simpson trial, in which DNA evidence was used. This made it particularly relevant because ALL the kids had heard about the trial.
You can begin the activity by talking a bit about what DNA fingerprinting is, and how it's used. You can then tell the kids what a great audience they've been and that you've brought along cookies for them. Next, bring out a broken, empty container. We use a jar with a piece broken out of it, and some red food coloring on the broken part to simulate blood. Tell the kids that someone stole the cookies and the class is going to investigate who did it. You can then bring out your "suspects". We generally use a bunch of stuffed animals, some of which have Band-Aids on their "hands". The kids immediately realize that the suspect was likely to have cut himself or herself, and would therefore be sporting a Band-Aid; those suspects that don't have Band-Aids on are therefore ruled out right away. Now explain that, fortunately, the suspect left some blood on the jar, and you can use this to help figure out who did it. Pretend to take the blood off the jar; then pretend to take blood samples from each suspect. Explain that you are going to extract DNA from the samples.
1. To simulate the DNA, we use large strips of posterboard, color-coded
to represent the different suspects' and the thief's DNA. They have
been precut, then laid out into the strips. When we pre-cut the strips,
we make sure that two of the strips are cut to the same pattern as
Below is an example. You would likely want to actually have 4 or more suspects:
Thief: Red posterboard Suspect 1: Blue posterboard
Suspect 2: Green posterboard Suspect 3: Black
2. Next you explain that you will use restriction enzymes. These enzymes are basically like scissors - they "cut" the DNA at defined places. To represent this, you take the poster board strips and pull the pieces apart.
3. Now you are going to separate the pieces. You want to use something that can separate pieces by size, so you will run the DNA in an agarose gel. You can explain that agarose is a complex matrix, almost like a spider web. Therefore, because it's easier for the smaller pieces to make their way through the "web", the small pieces will run down to the bottom of the gel, and the larger pieces will get "caught up" and stay more to the top. Now have the kids separate the posterboard pieces by size. They should come up with something like the following:
Thief's pattern: Suspect 1: Suspect 2: Suspect 3:
4. From the pattern, the students should decide which suspects can now be eliminated. Only two suspects will remain. Now it becomes more puzzling. How are the students going to tell which of these suspects actually committed the crime? You can ask the kids to come up with ideas. Hopefully someone will come up with the fact that each piece of DNA is made up of individual bases, and that these can vary between different animals' DNA - just like the individual whorls in a fingerprint that can distinguish each of us.
5. Now you should turn over the pieces of posterboard. On the back of each piece will be arrangements of DNA bases. Explain that, since you can directly see each base, you have a "marker" piece of DNA that binds every time it sees a certain pattern of bases. We often use the pattern "CAT" because it seems fitting given that the suspects are stuffed animals. Have a number of these markers, and have the students place them on every pieces of posterboard that has the sequence CAT. It should look like the following:
Thief Suspect 1 Suspect 2
Now the students should be able to see that Suspect 1 committed the
crime. You can then recover the stolen cookies
and give one to each kid.