Summer Research Program for Science Teachers

Traci Collier

HS for Information Technology, Queens

August 2003 

DNA Activities

v     Forty-minute blocks for sixth and seventh grades.

What is DNA?

Standards: S2a-e, S4a, S4b, S4d, and S5f.

Skills: Analysis, critical thinking, and deductive reasoning

Vocabulary: DNA (deoxyribonucleic acid), nucleus, cell, chromosome, gene, nitrogen base, gene, double helix, adenine, guanine, thymine, and cytosine.

Curriculum Integration: Physical Science, Communication Arts, and Biology.

Motivation: Do you remember or recall the O.J. Simpson trial and usage of DNA evidence?

Materials: Handouts, scissors, glue, paper, and DNA nucleotides.

Lesson Development (including key questions):

Mini-Lesson

DNA is the chemical that makes up chromosomes.  DNA stands for deoxyribonucleic acid.  Heredity is determined through DNA.

Ø      DNA’s structure is that of a double helix shaped liked a spiral staircase.

Ø      Sugars and phosphates form the sides of the staircase.

Ø      The steps are formed by four kinds of nitrogen bases: adenine, guanine, thymine, and cytosine.

Ø      Inside the nucleus is where chromosomes are located. On a portion of the chromosome is where your genes are located.

Ø      A gene is the portion of a chromosome that controls a particular trait.  Genes contain information needed for cells to function.  They are arranged along the length of the chromosome.

Ø      An individual receives 23 chromosomes from each parent.

Ø      Each cell’s DNA is the same throughout your body.  (i.e. hair cells have the same DNA as a liver cell) except in RBCs because they lack nuclei.

Ø      The DNA code, which is formed by the nitrogen bases, is highly specific.

Ø      A-T C-G never A-C or G-T

Medial: Define gene in the context of DNA. List the four nitrogen bases.

LD Continued:

Hands-on activity:

What is the structure of DNA? Students will at this point build their own DNA structure.

Summation:

Ø      DNA stands for deoxyribonucleic acid.

Ø      It is the chemical that makes up your chromosomes

Ø      It has a double helix shape.

Ø      There are sugars and phosphates located in DNA.

Ø      The nitrogen base pairs are Adenine, Thymine, Guanine, and Cytosine

Homework

Construct 3-D model of DNA due two weeks from today’s lab.

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Ninety-minute Blocks: Laboratory

Who are Ralph’s parents? A lab on DNA fingerprinting and Paternity

Standards: S1a-d, S2a-d, S4a-d, S5a-f, S6a-c, S7a-d, and S8d

E2a, E3a-c, e and E4a

Skills: Analysis, Critical thinking, Deduction, and COOP learning.

Vocabulary: DNA fingerprint, cell, nucleus, chromosome, gene, and paternity.

Materials:  Ralph’s DNA fingerprint, scissors, glue, paper, pens, and pencils.

Motivation: Begin a discussion on DNA fingerprinting as evidence O.J Simpson trial and CSI TV show.

Curriculum Integration: Biology, Communication Arts, and Forensics

Background information:

·        DNA fingerprinting is based on analyzing an individual’s DNA, deoxyribonucleic acid, a molecule that is found in almost every cell of one’s body.  DNA of all humans is similar, but it varies enough from one person to the next to give each person a unique DNA signature.

·        A gene is the portion of a chromosome that controls a particular trait.  Genes contain information needed for cells to function.  They are arranged along the length of the chromosome.

·        An individual receives 23 chromosomes from each parent.

·        Each cell’s DNA is the same throughout your body.  (i.e. hair cells have the same DNA as a liver cell) except in RBCs because they lack nuclei.

·        DNA has to be cut into fragments in order to be studied.

·        DNA has to be cut specifically by molecular scissors called restriction enzymes.

·        Restriction enzymes recognize specific six base pair sequences and cut the DNA strand wherever they come across the specific sequence.

Teacher’s Notes

1.      Students need 60 minutes for to complete this lab.

2.      In this lab, students are asked to be creative and draw some fictitious DNA fingerprints, then write a story about them.  Therefore, be sure that students understand the information given.

3.      Here are some possible drawings.

4.      Following is an evaluation rubric  which you can use to grade this lab.

Name________________________     Date______________________

Answers to Postlab Questions

1.      No. A child inherits DNA from his or her mother and father.  Therefore, some of the child’s DNA will be like the father’s and some will be like the mother’s.

2.      To prepare someone’s DNA fingerprint, cells are removed from that individual.  The DNA extracted from those cells, then cut into small pieces with restriction enzymes.  Because everyone’s DNA is different, everyone’s DNA is cut  into different sizes and numbers of pieces.  By analyzing the DNA pieces, an investigator can distinguish one individual from another.

3. DNA is in the nucleus of every cell except for RBCs.

Begin Hands-on Activity

Read lab procedure with students.

Medial: What cells do not possess a nucleus?  What are restriction enzymes? What is a DNA fingerprint?

Lesson Development continued:

Summation:

ü      DNA is found in every cell except RBCs.

ü      Each person has his or her own unique DNA fingerprint.

ü      Restriction enzymes are molecular scissors used to cut DNA.

Homework

Write a short story based upon the concept of the lab using scientific vocabulary.

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How to investigate incriminating evidence through DNA Gel Electrophoresis

Standards: S1a-d, S2a-d, S4a-d, S5a-f, S6a-c, S7a-d, and S8d

E2a, E3a-c, e and E4a

Skills: Analysis, Critical thinking, Deduction, and COOP learning.

Vocabulary: DNA, fragments, restriction enzymes, base pair, and eppendorf tubes.

Materials: DNA samples, DNA size standard, restriction enzymes (EcoRI, and SmaI), distilled water, Styrofoam test tube rack, P10-P100m, eppendorf tubes, DC power supply, aluminum pie plate, light box, methylene blue, markers, and lab books.

Motivation: Begin a discussion on DNA fingerprinting as evidence O.J Simpson trial and CSI TV show.

Curriculum Integration: Biology, Communication Arts, Forensics, and Physical Science.

Background information:

·        DNA fingerprinting is based on analyzing an individual’s DNA, deoxyribonucleic acid, a molecule that is found in almost every cell of one’s body.  DNA of all humans is similar, but it varies enough from one person to the next to give each person a unique DNA signature.

·        DNA has to be cut into fragments in order to be studied.

·        DNA has to be cut specifically by molecular scissors called restriction enzymes.

·        Restriction enzymes recognize specific six base pair sequences and cut the DNA strand wherever they come across the specific sequence.

·        Fragments are loaded onto gel.  They are then exposed to an electrical field that cause the fragments to travel through the gel.

·        The rate and distance at which fragments can travel through the gel depends on their size.

·        The fragments form invisible bands throughout gel.  These bands are then transferred to a nylon membrane.

·        Radioactive DNA probes are added to the membrane.  Then X-ray film is placed over the probes on the membranes.

·        X-ray is developed, the probes have exposed it in places where DNA is located.  This film is a DNA print.

Teacher Notes:

(a)    Students require 2 to 3 hours to complete this lab.

(b)   Teacher preparation time for this lab is 3 to 4 hours.

(c)    Buy Edvotek Kit #109 which includes 6 kinds of DNA that have been cut with restriction en enzymes, 1 tube of practice gel loading solution, 4 micro-pipettes, 2 grams of agarose, 1 bottle of electrophoresis buffer, and 2 bottles of methylene blue-staining reagent.  Follow the instructions in the kit for preparing gels.  Store kit in refrigerator.

(d)   If you want students to pour their gels, they will need one class period to do so.  Poured gels can be refrigerated in electrophoresis buffer solution overnight.

(e)    Remove DNA samples and label them appropriately: Suspect 1 is Gloria and Suspect 2 is Suzanne. Suzanne committed the crime.  Maintain DNA samples on ice.

Answers to Post-lab Questions:

1.      Suzanne’s.  When cut with Sma I, her DNA bands matched those at the crime scene.

2.      They were the same.

3.      They were different.

4.      Because cutting their DNA with Eco RI did not show any difference, a second enzyme was used.

5.      Stain bands of DNA so they could be seen in the gel.

Begin Hands-on Activity:

Procedure:

1.      Place agarose gel in its gel bed into the electrophoresis gel chamber.

2.      Add enough electrophoresis buffer to the gel chamber to cover the gel.

3.      With a clean pipette, place 5ml. of Gloria’s DNA cut with Eco RI into well 1 in the agarose gel.

4.      With a clean pipette, place 5ml. of Gloria’s DNA cut with Sma I into well 2 in the agarose gel.

5.      With a clean pipette, place 5ml. of Suzanne’s DNA cut with Eco RI into well 3 in the agarose gel.

6.      With a clean pipette, place 5ml. of Suzanne’s DNA cut with Sma I into well 4 in the agarose gel.

7.      With a clean pipette, place 5ml. of crime scene DNA cut with Eco RI into well 5 in the agarose gel.

8.      With a clean pipette, place 5ml. of crime scene DNA cut with Eco RI into well 6 in the agarose gel.

9.      Place the top on the gel chamber and connect it to the power supply.  Plug in the power supply and adjust it to 100 to 150m volts.  Run gel for 30 minutes, or until the samples has almost completely crossed the gel.

10.  Turn off the power supply and slide the gel from the gel bed onto an aluminum pie plate.

11.  Cover the gel with methylene blue dye.  Leave gel in dye for 10 minutes or until blue bands of DNA appears on the gel.

12.  Pour the methylene blue into a stock bottle, then rinse the gel in water several times.

13.  Place the gel on the light box and compare the crime scene DNA with the other three samples. YOU ARE LOOKING FOR A MATCH.

Medial:  How is a DNA fingerprint made?

Summation:

q       DNA is unique.

q       DNA is technique that can be used for medicinal as well as criminal investigations.

Homework

To complete lab report answer postlab questions.  Double-spaced with 12 point font only due the end of week before classes.

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