Food for Thought:

            Prior Knowledge Investigation

 

 

 

                                                             Jenny Campbell

                                                                Fall 2005

 

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell – Prior Knowledge Investigation

 

Questions for Prior Knowledge Investigation:

 

1) What is DNA?

 

 

 

 

 

 

 

 

2) What does DNA do?

 

 

 

 

 

 

 

 

 

 

 

3) What makes up DNA?

 

 

 

 

 

 

 

 

 

 

4) Where can you find DNA?

 

 

 

 

 

 

 

 

5)  Can you sketch what DNA may look like? (use attached sheet)

Jenny Campbell

Prior Knowledge Investigation – Lesson Plan

 

Food for Thought

 

Purpose:

The purpose of this lesson is for students to the characteristics of DNA following the 5-E learning model.  By participating in discrepant events students will explore the characteristics of DNA and where DNA is found. Students will also explore the various aspects of DNA and the structure by participating in “Science fair Candy/Pasta DNA” assessment. 

 

Standards:

Virginia Standards of Learning:

 

LS.1     The student will plan and conduct investigations in which

d)   models are constructed to illustrate and explain phenomena;

g)   variables are controlled to test hypotheses, and trials are repeated;

i)    interpretations from a set of data are evaluated and defended; and

j)    an understanding of the nature of science is developed and reinforced.

 

LS.13   The student will investigate and understand that organisms reproduce and transmit genetic information to new generations. Key concepts include

a)      the role of DNA

 

National Science Education Standards:

Content Standard C:

a)      Reproduction and heredity

 

Materials and Resources:

Discrepant Event:

1)      2- 5 oz plastic cups

2)      blender

3)      plastic spoon for measuring and mixing

4)      #2 cone coffee filter

5)      20 ml of distilled water

6)      clear-colored shampoo, such as Suave Daily Clarifying Shampoo

7)      3- bananas

8)      table salt, either iodized or non-iodized

9)      1- plastic transfer pipette or medicine dropper

10)  1- glass stirring rod

11)  1- sealed test tube containing 95% ethanol (grain alcohol) or 91% isopropyl (rubbing) alcohol

12)  1- container with ice for cold alcohol tubes

 

 

Science Fair –DNA Model Assessment:

13)  Dry bowtie and ziti pasta

14)  Floral wire

15)  Styrofoam

16)  Yarn of 3-4 different colors

17)   Chenille of 4 different colors

18)  Construction paper

19)  Pom-Poms

20)  Straws

21)  Modeling Clay

22)  Marshmallows of 4 different colors

23)  Scissors

Throughout the Lesson:

24)  Activity Sheets and Instruction Sheets

 

Safety:

1)      Students should be careful if they handle the isopropyl (rubbing) alcohol, not to get any in their eyes or mouth or to splash on anyone else.

2)      There could be the potential for broken glass, students should be careful when handling test tubes and glass stirring rods when participating in the discrepant event and be careful with scissors.

3)      The teacher should also note if there are any students allergic to bananas.

4)      Students should not use the medicine dropper to squirt liquid near or on anyone.

 

Procedure:

Timeframe: This lesson plan is designed for two 40 to 45-minute classes.

 

Day One:

Engage:

1)      The teacher will engage the students and have them explore DNA characteristics and where it can be found by demonstrating or allowing the students to participate in “Food for Thought” discrepant event.   See attached instructions for “Banana DNA” experiment, due to time availability the teacher will have prepared the lab until step 4, at which point the students can take over. (15 min)

Explore:

2)      The teacher will engage the students by asking a series of open-ended questions about DNA.  Examples may include: “When you hear the word DNA what do you think of?”  (5 min)

Explain:

3)      The teacher and students will engage in a discussion about the various characteristics of DNA, i.e. where it can be found, what it is composed of, and what it looks like.  The teacher will also incorporate the history of DNA into the discussion, focusing upon James Watson, Francis Crick and Rosalind Franklin. (20 min)

4)      Students will be given an activity sheet to be filled out along with the discussion.  The sheet will be composed of open-ended questions and will also serve as a guideline for students to write down information gained during discussion. (To be done along with discussion)

Day Two:

Elaborate:

5)      Students will elaborate upon what they have learned by constructing their own model of DNA from candy or pasta provided.  The students will choose which ingredient will serve as each part of the DNA.  The students will have a time limit of 25 minutes to complete their “Candy or Pasta DNA.”   The model should include all aspects of DNA covered in previous classes. Students can work on this in pairs or groups that the teacher has chosen or students may chose their own groups. (25-30 min)

6)      After constructing their model of DNA, the students will be given a list of groups and will be asked to judge the other models of DNA, “Science Fair Style”.  The only stipulation is that the students’ cannot vote for their own model.   The winner will be awarded a prize of the teacher’s choice, perhaps homework pass or ribbon.  (10-15 min)

 

Evaluate:

Performance Criteria

Evidence

Points

Students should be able to identify and demonstrate the structure of DNA.

Completion of DNA activity sheet, participation and completion of DNA model.

 

Students should be able to identify the various parts of DNA.

Completion of DNA activity sheet participation and completion of DNA model.

 

Students should be able to identify where DNA can be found and what may/may not have DNA.

 

Completion of DNA activity sheet and participation in class discussion/activity.

 

 

5 = completes activity and explanation without mistakes

3 = completes activity but offers incomplete explanation.

0 = does not complete activity or explanation

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell – Prior Knowledge Activity Sheet

Food for Thought

 

Purpose:  Complete the lab activity below with your partner then answer the two questions below with the information you gathered from completing the lab.

 

What you’ll need:

1 – Plastic cup with mystery mixture

1 – Plastic cup (empty)

1 – Coffee filter

1 – Medicine dropper

1 – Sealed test tube of rubbing alcohol

1 – Glass stirring rod

 

What you need to do:

1)      Place the coffee filter inside the empty plastic cup. Fold the coffee filter's edge around the cup so that the filter does not touch the bottom of the cup.

 

2)      Filter the mixture by pouring it into the coffee filter and letting the mixture drain for several minutes until the bottom of the cup is covered with the drained mixture.

 

3)      Obtain a test tube of cold rubbing alcohol from Mrs. Campbell.

 

4)      Fill the medicine dropper with the mystery mixture that has filtered to the bottom of the cup and add it to the test tube of rubbing alcohol.

 

5)      Let the solution sit for 2 to 3 minutes without disturbing it. It is important not to shake the test tube. You can watch a white stringy substance (it will look mucus-like) precipitate out into the alcohol layer.

 

6)      After letting the mixture sit for 2 to 3 minutes, use the glass rod to try to pull some of white, stringy material out from the bottom of the test tube.

 

After completing the lab, answer the questions below:

 

1) What do you think is the white stringy material that was in your test tube?

 

 

 

2) Where do you think it came from?

 

Now carefully rinse out your test tubes and your cups then set both of them back at your lab station, and then please take your seat. J

Jenny Campbell – Prior Knowledge Activity Sheet

 

More Food for Thought

 

Purpose:  Fill in the blanks and questions with information you gather during class.

 

 

What do you think the letters DNA stand for?

 

 

 

 

 

 

Where can you find DNA?

 

DNA is stored in ­_________ that have a _________.

 

 

 

What does DNA do? What is it?

 

DNA is a __________ that contains information for an organism’s _________ and __________. 

 

When a cell divides the DNA is ________ and passed on to new cells.

 

 

Discovering DNA

 

Since the mid-______ scientist have known that the nucleus of the cell contains some sort of large molecules.  But it was not until around ______ that scientist learned what DNA was made of.

 

 

A little history:

 

Scientist ___________  ___________ discovered that DNA was two chains in a spiral form in the year ______.

 

By _____ two other scientists James Watson and ____________  ____________ made a model of DNA.

 

 

 

 

 

But what does DNA look like? What is it made of?

 

If you were to see DNA up close you would see that it looks like a ___________ ____________.   This is called a double helix.

 

The sides of the ladder are made of __________ and phosphate. 

 

The rungs are ladder are made of molecules called nitrogenous bases.  There are ______ kinds of nitrogenous bases that are found in DNA.

 

The bases in DNA are:

_________________ or (A)

 

_________________ or (G)

 

_________________ or (C)

 

_________________ or (T)

 

 

These bases are paired together to form each rung of the ladder. 

 

 

Adenine always pairs with _______________. 

 

Guanine always pairs with _______________.

 

 

 

Draw a picture of DNA below: 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell – Prior Knowledge

 

Food for Thought lesson plan – lab instructions

 

Prepared by the Office of Biotechnology, Iowa State University

 

Extracted Banana DNA lab instructions:

 

In this laboratory experiment students will extract DNA from bananas that have been blended with water. A portion of the banana mixture is then treated with shampoo and salt, mixed for 5-10 minutes, and then strained through a coffee filter. The filtrate is added to cold alcohol and the DNA from the banana solution precipitates (becomes visible).

 

Materials:

  • 2- 5 oz plastic cups
  • blender
  • plastic spoon for measuring and mixing
  • #2 cone coffee filter
  • 20 ml of distilled water
  • clear-colored shampoo, such as Suave Daily Clarifying Shampoo
  • 3- bananas
  • table salt, either iodized or non-iodized
  • 1- plastic transfer pipette or medicine dropper
  • 1- sealed test tube containing 95% ethanol (grain alcohol) or 91% isopropyl (rubbing) alcohol
  • 1- container with ice for cold alcohol tubes

Procedure:

1)      In a blender, mix a ratio of one banana per one cup (250ml) of distilled water. Blend for 15-20 seconds, until the solution is a mixture.

2)      In one of the 5 oz cups, make a solution consisting of 1 teaspoon of shampoo and two pinches of table salt. Add 20 ml (4 teaspoons) of distilled water or until the cup is 1/3 full. Dissolve the salt and shampoo by stirring slowly with the plastic spoon to avoid foaming.

3)      To the solution you made in step 2, add three heaping teaspoons of the banana mixture from step 1. Mix the solution with the spoon for 5-10 minutes.
(The detergent dissolves the lipids that hold the cell membranes together, which releases the DNA into the solution. The detergent causes lipids and proteins to precipitate out of the solution, leaving the DNA. The salt enables the DNA strands to come together.)

4)      While one member of your group mixes the banana solution, another member will place a #2 cone coffee filter inside the second 5 oz plastic cup. Fold the coffee filter's edge around the cup so that the filter does not touch the bottom of the cup.

5)      Filter the mixture by pouring it into the filter and letting the solution drain for several minutes until there is approximately 5 ml (covers the bottom of the cup) of filtrate to test.

6)      Obtain a test tube of cold alcohol. For best results, the alcohol should be as cold as possible.

7)      Fill the medicine dropper with banana solution and add it to the alcohol.
(DNA is not soluble in alcohol. When alcohol is added to the mixture, the components of the mixture, except for DNA, stay in solution while the DNA precipitates out into the alcohol layer.)

8)      Let the solution sit for 2 to 3 minutes without disturbing it. It is important not to shake the test tube. You can watch the white DNA precipitate out into the alcohol layer. When good results are obtained, there will be enough DNA to spool on to a glass rod.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell – Prior Knowledge

 

Food for thought discussion guide day two:

 

Ask:  Where is DNA stored?

 

Ask:  What does DNA look like?

 

Ask: What are the sides of the ladder made of?

 

 

Ask: What are the rungs made of?

 

 

 

Instructions for Model:

 

  • Needs to have sugar, phosphate and the 4 nitrogenous bases.
  • You and your partner will have _______ minutes to finish it.
  • It doesn’t have to have the curve b/c it is hard to put the curve in there with materials, so you can make it straight up and down if you would like, as long as it has the parts, but if you want to put the twist in there that’s fine.
  • If you want to make it stand up, make your model first, the see me about getting a piece of Styrofoam to use.
  • You and your partner can use any of the parts I have given to you, if you can’t use any of the parts come talk to me. 
  • You will get marshmallows in your kit you do not want to eat them -- they are not food-quality.
  • You also do not want to poke anybody or throw anything across the room or at someone. 
  • Once you finish your project clean up your area and then we’ll be ready for the judging!!
  • Once you get your partner, go to your station and start your model. 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell – Prior Knowledge Activity Sheet

 

 

My Group Number: ________

 

 

 

Most Creative DNA Model is:

 

 

Group Number: ________

 

 

 

 

 

 

 

Most Accurate Looking DNA Model:

 

Group Number: ________

 

 

 

 

 

 

 

DNA Model that Used the Most Materials:

 

Group Number: ________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jenny Campbell

Prior Knowledge Investigation – Assessment

 

            I chose to do my prior knowledge investigation on the structure and function of DNA.  I chose to focus the investigation on DNA for several reasons:  One, DNA is going to be an integral part of their scientific careers as well as their lives.  Another reason I chose DNA was we had already covered cells and cell components and I was intrigued to see if they recalled any of the cell component information.  Also, I have a great interest in genetics and wanted to see for my own interest what the students previously knew.  Finally, I was interested to see if TV and movies influenced their view of DNA. 

            I began my investigation by interviewing three students.  These students were all of average ability and chosen at random.  I asked the three students the same 4 questions and asked them to diagram a picture of what they thought DNA looked like.  The four questions were:

1)      What is DNA?

2)      What does DNA do?

3)       What makes up DNA?

4)      Where can you find DNA?

5)      Sketch what you think DNA may look like.

 

            I received varied answers from the students.  I was expecting students to have partial knowledge of DNA; I was expecting them to have at least heard of it before.  I expected answers like “DNA is your blood or hair” and “DNA makes up you”.  I was not expecting them to know the structure of DNA.  The results received from the interview confirmed my expectations.  Student 1 answered the question about what DNA is by stating, “It’s your hair, it’s yourself”.  Student 2 said “Something in your blood” while student 3 had a different answer “I don’t know.  It tells you who you are.”  Student 1 had a very interesting answer to the question what does DNA do, the student stated: “They can take DNA to figure out what’s wrong with you, like if you’re sick.”  Student 2 did not know, while student 3 said it gives your hair and blood.  Student 1 and 2 answered that they did not know what makes up DNA, while Student 3 said “cells.”  To the final question, the students did not answer that DNA would be in cells, but students 2 and 3 said you could find DNA in your body while student 1 said it could be found everywhere, or “in science labs.”   Finally I had the students draw a representation of what they believed DNA would look like, their drawings are below:

 

Student 1 Drawing of DNA

 

 

                                               

Student 2 Drawing of DNA

                                                                                                                       Student 3 Drawing of DNA            

                Based on the answers I received during my interviews, I designed my lesson plan to showcase that DNA was in all organisms, where it is located within the body and cell and DNA’s structure.  The lesson covered a few Virginia Standards of Learning including: LS.1 The student will plan and conduct investigations in which d) models are constructed to illustrate and explain phenomena; g) variables are controlled to test hypotheses, and trials are repeated; i) interpretations from a set of data are evaluated and defended; and j) an understanding of the nature of science is developed and reinforced.  As well as LS.13: The student will investigate and understand that organisms reproduce and transmit genetic information to new generations. Key concepts include a) the role of DNA.  Other standards covered were also the National Science Education Standards, Content Standard C: reproduction and heredity.

             I began my two-day lesson with a discrepant event that involved extracting DNA from a banana.  However, I did most of the prep work and did not allow the students to see that the material that we were using was a mixture of banana and shampoo.  I gave the students instructions for the actual extraction that would allow them to see the results, which was a white mucus-like substance in a test tube of rubbing alcohol.  On the instruction sheet also were two open-ended questions, “what do you think that white substance is?” and “where did it come from?”  Once the lab was completed we then discussed what the students believed the substance to be.  During the first period, students gave a variety of guesses including: soap, shampoo, bacteria and DNA.   The students guessed soap and shampoo due to the consistency of their mystery mixture, bacteria because they were getting ready to study that and DNA because one of the students recognized a model I had sitting out.  However, third period were not as varied in their answers, mostly they guessed soap or shampoo, no one said bacteria or DNA (although, in all fairness I had put away the model).  In both classes, the students were taken aback that they had just been witness to DNA and were even more surprised that is was DNA from a banana, especially since all of their guesses as to where it came from was human-related. 

            I followed up the lab with a discussion on the basics of DNA, including function, location and structure.  The second day of the investigation was started by a review of the previous day’s discussion, the students seemed eager to give out some answers, all of them correct.  The review was followed by a model building activity.  The students were given a variety of materials including: chenille pipe cleaners, marshmallows, yarn, straws, floral wire and Styrofoam.  The only restrictions were that the model needed to include, sugar and phosphate backbone and the four nitrogenous bases paired correctly.  If the students chose to, they could twist it (it was not a requirement, due to the difficulty of twisting their given materials, but most students chose to) and it did not have to stand up.  The students then participated in a “science fair” afterwards, mainly a motivation set by me in order to get the students to finish the project within the 30 minutes I had given them, because unfortunately we would not be able to spend anymore days on DNA.  The students then chose their favorite in the categories: “most creative”, “most accurate” and “used the most materials.”  Only one group of 18 did not finish the model in time.   The models and teams were then assessed by me based on the specified criteria above and amount of team participation, they were given 10 points for if they fulfilled all requirements, 9 points if their model was missing parts but had good participation and 7 points if they were not cooperative with their partners.  All those students interviewed received 10 points.  I feel that based on the interviews then the discussion and activities the students have a better understanding of DNA, where it is found, it’s function and of course it’s structure.  The students constructed very good models of DNA and were very active in discussion and review. 

 

Below are pictures of the models completed by the students, including the students that participated in the interviews.

 

Student 1 and partner (straws are holding the structure in place)
 

Students 2, 3 and partner

 
 
 

 


                                                                                  

 

 

 

            I found this to be a very interesting project to complete.  The students seemed to pull away a bit more knowledge than they previously had before, I found this was evident in their models as well as speaking with the students one-on-one and reviewing discussions from the previous day.  I can see why it is important to gain a student’s prior knowledge before beginning a new lesson, it can determine where your students stand as well as hopefully clearing misconceptions so they do not carry them further in the school career.  Reading Baker and Piburn, it was interesting and almost alarming to see what misconceptions were strewn about in the life sciences.  One of my students stated that DNA was made of cells, she had knowledge of cells previously and that they made up all things living, but may not have considered DNA being smaller than the cell.  I can see her reasoning: living things have cells; DNA makes up characteristics of living things, so DNA must have cells. According to Baker and Piburn, most high school students know nothing or not much about cells, so at least the student is aware that living organisms are composed of cells.   I was little surprised at the students lack of knowledge (or misconceptions) on the subject of DNA, for the simple reason there is an abundance of television shows and movies where DNA is the focus; since this is considered to be part of where students gather misconceptions, the real world and the classroom (Baker 1997). 

            All in all, I found the students did have some misconceptions about DNA that were addressed in my lesson.  I can see why this is so important to the field of education; students should not be walking through school, much less through life, without the correct information to allow them to lead them through life. 

 

 

 

 

Works Cited

 

Baker, D.R. and Piburn, M.D. Constructing Science in Middle and Secondary School

            Classrooms. Allyn and Bacon, 1997.