Lesson DNA:
The Human Body Recipe

Quick Look

Grade Level: 6 (5-7)

Time Required: 15 minutes

Lesson Dependency: None

Quick Look

Grade Level:
6 (5 – 7)
Time Required:
15 minutes
Discuss this lesson

TE Newsletter

Graphic shows images of DNA helix, gene, chromosomes and cell, with headline: DNA – the molecule of life.
The instructions for creating all the cells in our bodies are found in our DNA.
copyright
Copyright © Human Genome Program, US Department of Energy, Genome Management Information System, Oak Ridge National Laboratory http://genomics.energy.gov

Summary

As a class, students work through an example showing how DNA provides the "recipe" for making human body proteins. They see how the pattern of nucleotide bases (adenine, thymine, guanine, cytosine) forms the double helix ladder shape of DNA, and serves as the code for the steps required to make genes. Students extend their knowledge by conducting the associated activities to learn ways that engineers and scientists are applying their understanding of DNA in our world.

Engineering Connection

Once it was discovered that DNA contains the instructions for making cells and proteins, the way was open for many diverse engineering applications. Genetic engineers find ways to modify the DNA of organisms to create a desired trait or protein, such as making a crop resistant to a certain herbicide or making bacteria that create human insulin. Forensic engineers use DNA evidence to help determine people's innocence or guilt of crimes. Agricultural engineers create genetically-modified crops to enable the cultivation of food in areas poorly suited for farming.

Learning Objectives

After this lesson, students should be able to:

  • Describe DNA (deoxyribonucleic acid).
  • Describe ways in which engineers are involved with genetics and the human body.

Introduction/Motivation

If you want to bake a batch of chocolate chip cookies, what would you need? You probably need some chocolate chips, flour, sugar, butter and eggs. And maybe some nuts or rolled oats if you like. But, how do you know how to make it? By using a recipe! A recipe contains the instructions for how to put all the ingredients together to make the cookies.

Now let's say instead of making chocolate chip cookies, you wanted to make a person! What would you need? (Write on the board an "ingredient list" generated by the students; it might contain: a father [sperm], a mother [egg], uterus, food, proteins, bones, muscles, organs, air, water, elements, minerals, etc.) (After the list is created, ask the students the following question.) And, where is the recipe that tells us how to combine all the ingredients to make a human? (Take suggestions from the students.) That's right, our DNA contains the recipe for making the cells and proteins in our bodies.

Drawing of a twisted ladder-like structure with color-coded and paired adenine, thymine, guanine and cytosine cross structures, positioned like rungs.
Figure 1. DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.
copyright
Copyright © US National Library of Medicine, National Institutes of Health http://ghr.nlm.nih.gov/handbook/illustrations/dnastructure

DNA stands for deoxyribonucleic acid. DNA is a pair of molecules usually found in each cell's nucleus that contains codes (the recipe) for the proteins that make our body tissues (show students Figure 1 or a similar DNA representation).

DNA is made of two long molecules that are hydrogen-bonded between the base pairs. (The hydrogen bond is an intermolecular force induced by the pulling away of hydrogen's electron by one base [giving hydrogen a positive charge] and the negative charge of the other base nearby). The base pairs—adenine (A) bonding with thymine (T), and cytosine (C) bonding with guanine (G)—form a code down the length of the DNA.

The order of the nucleotide bases forms a code that specifies which proteins our cells make, and consequently tells our cells what to do. Imagine untwisting the DNA (see Figure 1) and spreading it out flat so that we can see the order of the nucleotide bases. Let's write down the order of the nucleotide bases as an example. (Write the following on the board.)

Example DNA coding showing A, C, T, G base pair bonds between two DNA strands.

Notice how the nucleotide bases are matched to form base pairs. These pairs are the actual recipe for making proteins. (To teach the students more about making proteins, or protein synthesis, see the example in the Lesson Background section.)

Now that you understand that DNA contains instructions, let's talk about genes. A gene is a segment of DNA that gets translated into a protein. Genes are more commonly thought of as units for heredity, such as the gene for brown eyes or the genes responsible for being tall or having high blood pressure. DNA, and consequently genes, is passed from a father to his offspring through his sperm, and from a mother to her offspring through her egg. Children have a 50-50 mix of DNA from their parents. Humans have about 25,000 genes. Any two people, though they look different and may come from opposite ends of the world, are 99.9% similar in their genes. Our genetic make up is 98% the same as chimpanzees, 92% the same as mice, and 18% the same as weeds. Clearly, tiny differences in our genes can cause huge physical differences!

Our growing understanding of genetics has led to many diverse engineering applications, including ways to improve crops, catch criminals, detect diseases and determine paternity and ancestry. For many different applications, engineers design DNA collection and analysis tools, equipment and processes. Biomedical engineers specializing in genetics find ways to modify the DNA of organisms to create a desired trait or protein (such as making bacteria that create human insulin).

Just as children inherit their hair or eye color from their parents, they can also inherit genetic diseases. DNA medical analysis has provided the ability to pinpoint the cause of human genetic disease and detect individuals who are predisposed to inherited diseases (such as genetic liver disease). Modern medicine cannot prevent inherited diseases, but can often improve a person's health and life expectancy through engineered treatments.

DNA breakthroughs have led to engineered techniques and tools to rapidly detect and identify outbreaks of infectious diseases, such as severe acute respiratory syndrome (SARS virus). Biomedical engineers help public health practitioners track down the source of infectious disease outbreaks, whether from natural or human sources, which saves many lives. Refer to the DNA Profiling & CODIS: Who Robbed the Bank? activity to have students use DNA profiles to have crack mystery cases! Then have students expand their knowledge with the DNA Build activity by building DNA models to investigate codes relating to certain physical characteristics such as eye and hair color.

Lesson Background and Concepts for Teachers

The Study of Genetics

Gregor Mendel (1822-84) was the first scientist to study genetics through the study of peas. He used pea plants because they were easy to cross-pollinate and fast to see changes in the plants. He studied certain characteristics of pea plants, such as height. He noticed that by cross-pollinating short and tall plants, he could get a certain number of tall plants and a certain number of small plants, depending on the generation. In comparing his study of peas to humans, he found that each pea received its traits from its parent plants. Mendel came up with principles that still hold true today.

The Science of Genetics

Cells are in all living things, and contained within each cell is a nucleus. Within the nucleus is genetic information, in the form of chromosomes, which make up DNA strands. Forty-six chromosomes make up the average human cell. Twenty-three chromosomes have 23 pairs. Red blood cells, sperm and eggs are the only cells in the human body that do not have 46. In human reproduction, a sperm joins an ovum to create a zygote, which has chromosomes made of genes that decide what the baby will look like.

Diagram illustrates steps from chromosomes to proteins.
copyright
Copyright © 1997 Human Genome Program, US Department of Energy, Human Genome Program Report http://genomics.energy.gov

Protein is an important component in the body; it is the building block for everything in the body. Protein is made from the "recipe" contained in the gene. A gene is made from DNA. DNA is arranged in a special pattern that has the recipe contained within in it to make the genes. Each DNA strand is unique to the individual from where it resides. The recipe is known as DNA code. Some people picture a DNA strand as a ladder, with each rung of the ladder made from a pair of DNA letters representing the nucleotide bases. The letters are A, T, G and C, with A only binding to T, and G only binding to C. The binding of these letters forms base pair bonds in a double helix shape.

Protein Synthesis

Protein synthesis is how a piece of DNA provides a code for how to make proteins. In the cell's nucleus, a protein called RNA (ribonucleic acid) polymerase attaches to the DNA strand, stretches it out and separates a section of it:

Example DNA strand 1 coding: T, A, C, A, C, G, G, A, G, A, T, C.

Now, the RNA polymerase travels down this strand and uses these bases as a template for creating mRNA (messenger RNA). It is called messenger RNA because it carries the message coded by these bases to the ribosomes outside the cell nucleus.

Added below the previous example DNA strand 1 coding, an example mRNA coding for that strand: A, U, G, U, G, C, C, U, C, U, A, G.

Note that the mRNA is a copy of DNA strand 2 except that uracil (U), another nucleotide base, replaces thymine (T) in mRNA. As the mRNA is made, the RNA polymerase reattaches DNA strand 1 and DNA strand 2.

The mRNA travels outside the cell's nucleus into the cell's cytoplasm and then attaches to ribosomes, which are proteins that can be thought of as cells' protein factories. The ribosome reads the mRNA in sets of three bases, called codons. The codons specify which amino acids, the building blocks of proteins, are made. In our example, a ribosome would travel down the DNA in several steps, making a protein specified by the amino acids called for by each codon:

Step 1: Ribosome reads codon AUG, which means Start Translation (start making protein).

A ribosome is placed above the first three bases (a codon) of our example mRNA coding, A, U, G.

Step 2: Ribosome reads codon UGC, which means make the amino acid cysteine.

A ribosome is placed above the second three bases (a codon) of our example mRNA coding, U, G, C, with a tail indicating it has made the amino acid cysteine.

Step 3: Ribosome reads codon CUC, which means make the amino acid leucine.

A ribosome is placed above the third three bases (a codon) of our example mRNA coding, C, U, C, with a tail indicating it has made amino acids cystein and leucine.

Step 4: Ribosome reads codon UAG, which means End Translation.

A ribosome is placed above the fourth three bases (a codon) of our example mRNA coding, U, A, G. Nearby a protein of cysteine and leucine floats free in the cell.

(See a complete list of codons and the amino acids they specify in the Wikipedia RNA codon table at http://en.wikipedia.org/wiki/Codon.)

The protein made in our example does not really exist; it just illustrates how DNA contains the codes necessary for protein synthesis and how protein synthesis is carried out. An example of a real protein coded for by DNA is the hormone insulin, which controls the concentration of glucose in our blood. Insulin is made of 51 amino acids.

To summarize, DNA contains nucleotide base codes that are transcribed by RNA polymerase to make mRNA, which takes the code from the nucleus of the cell to the ribosomes in the cytoplasm. The ribosomes translate the codons in the mRNA to make amino acid chains that become proteins. These proteins regulate how our body functions and how we develop.

Lesson Closure

Tell me what you know about DNA. (Expected answers: DNA is found in the nucleus of our cells. It is like a recipe. It is shaped like a double-helix ladder. The backbone is made of deoxyribose, a sugar phosphate, and the ladder rungs are the nucleotide bases. The nucleotide bases are the codes for the proteins that our cells make. A gene is a segment of DNA that gets translated into a protein.)

What are the ways that scientists and engineers are using our understanding of DNA? (Possible answers: To detect inherited diseases in people; to identify infectious diseases and track down their sources; for diagnosis, treatment and [possibly] prevention of human diseases such as cancer, cystic fibrosis and heart disease; to modify organisms for a desired trait or protein; to improve crops; to catch criminals; to examine DNA as part of crime, paternity and ancestry investigations.)

Vocabulary/Definitions

biomedical engineering: The application of engineering techniques to the understanding of biological systems and the development of therapeutic technologies and devices. Kidney dialysis, pacemakers, synthetic skin, artificial joints, and prostheses are some products of biomedical engineering. Also called bioengineering.

DNA: Deoxyribonucleic acid contains the genetic instructions that control the biological development of our cells and the proteins the cells make. DNA codes the sequence of the amino acids in proteins using the genetic code, a triplet code of nucleotide bases.

engineer: A person who applies his/her understanding of science and math to creating things for the benefit of humanity and our world.

gene: Segments of DNA that get translated into proteins.

nucleotide base: The part of RNA and DNA involved in pairing; it includes cytosine, guanine, adenine, thymine (DNA) and uracil (RNA), abbreviated as C, G, A, T and U. They are usually simply called bases in genetics. Also called base pairs.

protein synthesis: The process by which proteins are made. DNA nucleotide base codes are transcribed by RNA polymerase to make mRNA, which takes the code from the nucleus of the cell to the ribosomes in the cytoplasm. The ribosomes translate the codons in the mRNA to make amino acid chains that become proteins.

ribosome: A tiny, round particle composed of RNA and protein that is found in the cytoplasm of living cells and serves as the site of assembly for polypeptides encoded by messenger RNA.

Assessment

Pre-Lesson Assessment

Discussion Question: Ask students to write a "recipe" for what it takes to make a human. Compare lists. Lead into a discussion of DNA and how it contains the "recipe" for our body.

Post-Introduction Assessment

Question/Answer: Ask students questions and have them raise their hands to respond. Write their answers on the board.

  • Where is the information stored for how to make our cells? (Answer: In our DNA, which stands for deoxyribonucleic acid.)
  • What is a gene? (Answer: A gene is a segment of DNA that gets translated into a protein.)
  • What are the ways scientists and engineers are using our understanding of DNA to benefit society? (Possible answers: To detect inherited diseases in people; to identify infectious diseases and track down their sources; for diagnosis, treatment and [possibly] prevention of human diseases such as cancer, cystic fibrosis and heart disease; to modify organisms for a desired trait or protein; to improve crops; to catch criminals; to examine DNA as part of crime, paternity and ancestry investigations.)

Lesson Summary Assessment

Engineering Impacts: We have learned that biomedical engineers develop the tools and processes to make possible DNA analysis to modify and improve crops, catch criminals, detect diseases and determine paternity and ancestry. Biomedical engineers have even found ways to modify the DNA of organisms to create a desired trait or protein (such as making bacteria that create human insulin). Have students think about the potential abstract impacts of DNA engineering on society and the environment. Then assign students to choose one possible impact area (such as environmental, ethical, economical, societal [people]) and write a persuasive argument paragraph describing the possible impacts (positive and negative) on that area due to the engineering of DNA.

Lesson Extension Activities

Research & Report: Have students research the "human genome project" to find out what it is and why it is significant. Report back to the class on five important results from this research project. Start your research at Oak Ridge National Laboratory's About the Human Genome Project website: http://www.ornl.gov/sci/techresources/Human_Genome/project/about.shtml

Have students research genetically-modified foods, reporting to the class on whether they pose a health and/or environmental risk. In the laboratory, foods are genetically modified, selecting for desired characteristics. For example, in 1992 the FlavrSavr® tomato was created by modifying its DNA so that the tomato resists rotting. What about the modified fruits at the grocery store, advertised that they do not have seeds? What are the benefits? What are the controversies? Start your research at Oak Ridge National Laboratory's Genetically Modified Foods and Organisms website: http://www.ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml

Have students learn more about protein sysnthesis. Ask them to describe how a protein gets made, starting from its nucleobase code in the DNA. (Answer: The nucleotide base codes are transcribed by RNA polymerase to make mRNA, which takes the code from the nucleus of the cell to the ribosomes in the cytoplasm. The ribosomes translate the codons in the mRNA to make amino acid chains that become proteins.)

Additional Multimedia Support

Use interactive multimedia activities to explore some of the applications of DNA technology at Koshland Science Museum's Putting DNA to Work website: https://koshland-science-museum.org/exhibitdna/inf02.jsp?PF=1#.T_tOjFJ6DqM

Excellent DNA graphics and images suitable for PowerPoint presentations or color overhead transparences are available at the US Department of Energy's Human Genome Program's image gallery website: http://genomics.energy.gov/gallery/

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References

Blumberg, Robert B. (ed.) MendelWeb. Edition 97.1 (February 22, 1997). MendelWeb.

Gene. Last updated February 24, 2009. Wikipedia, The Free Encyclopedia. Accessed February 24, 2009. http://en.wikipedia.org/wiki/Genes

Genetic code. Last updated February 21, 2009. Wikipedia, The Free Encyclopedia. Wikimedia Foundation, Inc. Accessed February 24, 2009. (Includes a complete list of codons and the amino acids they specify in the RNA codon table) http://en.wikipedia.org/wiki/Codons

Genome Programs of the US Department of Energy. US Department of Energy. (Good resource for information and images)

Protein biosynthesis. Last updated January 16, 2009. Wikipedia, The Free Encyclopedia. Accessed February 24, 2009. http://en.wikipedia.org/wiki/Protein_biosynthesis

Copyright

© 2007 by Regents of the University of Colorado

Contributors

Frank Burkholder; Jessica Todd; Malinda Schaefer Zarske; Denise W. Carlson

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the DOE and NSF, and you should not assume endorsement by the federal government.

Last modified: September 6, 2024

Hands-on Activity DNA Profiling & CODIS:
Who Robbed the Bank?

Quick Look

Grade Level: 7 (6-7)

Time Required: 30 minutes

Expendable Cost/Group: US $0.00

Group Size: 2

Activity Dependency: None

Quick Look

Grade Level:
7 (6 – 7)
Time Required:
30 minutes
Group Size:
2
Discuss this activity

TE Newsletter

A drawing titled "Evidence & DNA" shows twisting double helix DNA strand and labeled evidence vial.
Students examine DNA to determine who robbed the bank
copyright
Copyright © President's DNA Initiative, US Department of Justice http://www.dna.gov/training/evidence/

Summary

Students use DNA profiling to determine who robbed a bank. After they learn how the FBI's Combined DNA Index System (CODIS) is used to match crime scene DNA with tissue sample DNA, students use CODIS principles and sample DNA fragments to determine which of three suspects matches evidence obtain at a crime location. They communicate their results as if they were biomedical engineers reporting to a police crime scene investigation.

Engineering Connection

Biomedical engineers who understand the science of genetics create tools, equipment and processes to accurately collect and examine DNA evidence for crime and paternity cases. These engineers also work with attorneys and in court systems to explain how DNA profiling works.

Learning Objectives

After this activity, students should be able to:

  • Describe the organization of DNA into repeating nucleotide base pair sequences
  • Explain how DNA profiling is used to link people to crime and paternity cases.
  • Describe the role of biomedical engineering in DNA profiling.

Materials List

Each group needs:

Worksheets and Attachments

Visit [www.teachengineering.org/curriculum/print/cub_biomed_lesson09] to print or download.

Pre-Req Knowledge

Familiarity with DNA and its constituent nucleotide base pairs.

Introduction/Motivation

A robbery takes place at a bank. As the thief escapes the building, a security guard grabs one of the bank robber's gloves. The bank robber leaves the scene in a phone service van. The phone company identifies three employees who may have been in the vicinity of the bank at the time of the robbery. All employees deny robbing the bank. Can you think of some way, besides witness testimony, that the bank robber could be identified from among the three individuals?

Two images: (left) a plastic-gloved hand holds a small vial containing a swabbed DNA sample. (right) A graphic shows the swirls and ridges of two fingerprints next to two strands of DNA sequences (black and white striped columns).
DNA evidence is more reliable than fingerprints at identifying people.
copyright
Copyright © (left) US Geological Survey, US Department of the Interior, http://www.nwhc.usgs.gov/disease_information/avian_influenza/gallery/pages/0025.jsp, (right) President's DNA Initiative, US Department of Justice http://www.dna.gov/training/evidence/

DNA can identify people — even better than fingerprints. DNA is found in all of our cells: hair, teeth, bones, blood and skin. Though all humans share 99.9% of their genes, our DNA differs from everyone else's by three million nucleotide base pairs.

Our DNA is organized in 23 chromosomes in the nucleus in each of our cells. Regions in each chromosome contain what are called "junk DNA," which does not contain genes. But often, this junk DNA contains repeating nucleotide base pair sequences that can be used for matching purposes. (Show students Figure 1 or the same image in the attached CODIS Visual Aid.) In this example, you can see chromosome locations where the FBI looks for repeating sequences of DNA. They're called CODIS sites, which stands for the FBI's Combined DNA Index System.

On a diagram showing many numbered columns with black, white and gray stripes, 13 CODIS sites are noted with their alphanumeric identifier in yellow highlight.
Figure 1. The 23 human chromosomes and 13 chromosomal locations at which the FBI looks for repeating DNA sequences. For this activity, note the TPOX region on chromosome 2. (X and Y count as one chromosome pair. The AMELs are not CODIS sites.)
copyright
Copyright © Biochemical Science Division, Chemical Science & Technology Laboratory, National Institute of Standards and Technology http://www.cstl.nist.gov/div831/strbase/images/codis.jpg http://www.cstl.nist.gov/div831/strbase/fbicore.htm

In our case, the police found a hair in the bank robber's glove. Remember that we have 23 pairs of chromosomes, each pair containing one chromosome from our father, the other from our mother. A DNA analysis shows that the hair in the robber's glove contains the following nucleotide base pair sequences in the TPOX region (show students Figure 2 or the same image in the attached CODIS Visual Aid).

A table lists base-pair sequences in chromosome from father (GC, AT, AT, TA, GC, AT, AT, TA) and chromosome from mother (GC, AT, AT, TA, GC, AT, AT, TA, GC, AT, AT, TA).
Figure 2. TPOX region of chromosome 2 of hair found in bank robber's glove.
copyright
Copyright © TL Program, College of Engineering, University of Colorado at Boulder.

Note that the GAAT sequence is repeated twice in the father's side and three times in the mother's side (the sides of each chromosome are often not the same length). Equivalently, we could say that the CTTA sequence is repeated. Why is that? (G always pairs with C, and A always pairs with T).

So now let's compare the TPOX regions of the DNA found in the bank robber's glove with the TPOX regions of the DNA of two suspects. Note that we are just looking at the one side of the DNA with the GAAT repeating sequence. This simplifies the comparison. (Show students Figure 3 or the same image in the attached CODIS Visual Aid.)

A table lists nucleotide base pair sequences in chromosomes from father and mother of three people, with the GAAT sequences in each highlighted in color.
Figure 3. Comparison of the TPOX region of Chromosome 2 of the unknown bank robber and two suspects.
copyright
Copyright © ITL Program, College of Engineering, University of Colorado at Boulder.

Suspect 1 matches the GAATGAAT sequence of the hair found in the glove on one chromosome, but the other chromosome does not match. Both chromosomes must match to show that the hair in the glove came from a specific suspect. Thus, from just one CODIS site we already know that the hair in the bank robber's glove cannot belong to suspect 1.

Suspect 2 matches the GAATGAAT sequence on one chromosome and the GAATGAATGAAT sequence on the other chromosome, so you can say that suspect 2 matches at the TPOX location. To confirm that the hair belongs to suspect 2, the other 12 chromosome locations (see Figure 1) must also match. If all 13 CODIS locations match, then the hair in the bank robber's glove belongs to suspect 2.

The random probability that one of your CODIS sites matches with someone else's is about one in 10 (1/10). Therefore, the probability of two CODIS sites matching is 1/10*1/10 = 1/100 (one in 100). The chance of three CODIS sites matching randomly is 1/10*1/10*1/10 = (1/10)3 = 1/1000 (one in 1,000). The random chance that all 13 CODIS sites match is (1/10)13 = one in 10,000,000,000,000. The chance of being struck by lightning in your lifetime is, roughly, one in 1,000,000. So you are 10 million times more likely to be struck by lightning than you are to have the same 13 CODIS sequences as another person. This is what makes DNA profiling so certain.

Engineers can be involved in many aspects of crime scene investigation. They might use their knowledge of CAD (computer-aided drawing) to create a reconstruction of the crime scene. First they might develop a model of the room, and then determine the path of bullets and analyze the blood splatter patterns to determine the position of victims and their killers at the time of the crime. Biomedical engineers create the tools, equipment and processes to accurately collect and examine DNA evidence for crime and paternity cases. Biomedical engineers also help investigators with the analysis of the gene sequencing for DNA profiling.

Procedure

Background

In this activity, probability is used to determine which suspect is the most likely match. We are told that the likelihood of a random match between a CODIS site for one person and someone else is 1/10. Why is that? Each of the regions that we are considering here contains an allele, or, a version of a gene. Which allele you have at a particular site is determined by your parents' genetic data and meiosis, as well as any errors in replication. However, these alleles are not unique in a population; you can have the same allele as someone else. Statisticians study populations to get an idea about the distribution of alleles (how many people have each kind of allele). In this way, statisticians can estimate a probability that any two people have the same allele. If the likelihood of a CODIS site match between two random people was much greater or much less than the 1/10 used in this activity, the number of matches we would need in order to be reasonably certain of the suspect's guilt would also change.

Before the Activity

With the Students

  1. Divide the class into pairs of students, and pass out a worksheet to each team.
  2. Assist students as they complete their worksheets.
  3. Have teams conclude by writing on their worksheets which suspect their DNA profiling implicates in the robbery.
  4. Have the teams with the correct answer describe how they arrived at their conclusion. (Answer: Suspect 2 seems likely based on a match with four CODIS sites).
  5. Have students calculate the likelihood that suspect 2, even though he matches four CODIS sites, is not the owner of the hair in the bank robber's glove. (Answer: (1/10)4 = 1 in 10,000, not good enough – need more CODIS site data)
  6. Have students act as biomedical engineers and analyze the results of the DNA profiling for the police investigators as described in the post-assessment activity.

Vocabulary/Definitions

base pair: Two nucleotide bases that form a "rung of the DNA ladder." A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the "letters" that spell out the genetic code. In DNA, the code letters are A, T, G and C, which stand for the chemicals adenine, thymine, guanine and cytosine, respectively. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine.

biomedical engineer: A person who blends traditional engineering techniques with the biological sciences and medicine to improve the quality of human health and life. Biomedical engineers design artificial body parts, medical devices, diagnostic tools, and medical treatment methods.

chromosome: One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes plus two sex chromosomes. Each parent contributes one chromosome to each pair, so children receive half of their chromosomes from their mothers and half from their fathers.

CODIS: Acronym for the FBI's DNA identification system: Combined DNA Index System. See: http://www.fbi.gov/hq/lab/html/codis1.htm

CODIS sites: The 13 regions of the chromosomes at which the FBI CODIS looks for repeating DNA sequences for matching purposes.

DNA: Deoxyribonucleic acid contains the genetic instructions that control the biological development of our cells and the proteins the cells make. DNA codes the sequence of the amino acids in proteins using the genetic code, a triplet code of nucleotide bases.

DNA fingerprinting: A method for identifying individuals by the particular structure of their DNA. Because the structure of each person's DNA is different, just like our fingerprints, we can be identified from our DNA. This technique became known to the public as "DNA fingerprinting" because of its powerful ability to discriminate between unrelated individuals.

DNA profile: The result of determining the relative positions of DNA sequences at several locations on the molecule. Each person (except identical twins) has a unique DNA profile when used in the context of the CODIS database, which evaluates 13 specific DNA locations.

engineer: A person who applies his/her understanding of science and math to creating things for the benefit of humanity and our world.

gene: Segments of DNA that get translated into proteins.

junk DNA: Stretches of DNA that do not code for genes; "most of the genome consists of junk DNA." Junk DNA contains repeating base pair sequences that can be used for matching purposes.

nucleotide bases: The parts of RNA and DNA involved in pairing; they include cytosine, guanine, adenine, thymine (DNA) and uracil (RNA), abbreviated as C, G, A, T and U. They are usually simply called bases in genetics. Also called base pairs.

Assessment

Pre-Activity Assessment

Discussion/Brainstorming: As a class, ask students if they can think of some way that a bank robber could be identified if no one saw who he or she was. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Brainstorming is how engineers come up with creative ideas. Have them raise their hands to respond. Record their ideas on the board.

Activity Embedded Assessment

Worksheet: Have students complete the activity worksheet; review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Engineering Analysis: Have students act as biomedical engineers and analyze the results of the DNA profiling for the police investigators. Have each team state which suspect their DNA profiling implicates in the crime. How certain are their results? Next, have the students write a brief one-page report on their results that they might deliver to the police investigators. In this report, they should explain the outcomes of the DNA profiling, how they arrived at their results, and how they determined the certainty of their results.

Safety Issues

  • Make sure students use care with scissors.

Troubleshooting Tips

If students have difficulty, work through the first CODIS site on the worksheet with them.

Sometimes it helps to cut out the robbery evidence CODIS data columns from the worksheet and hold them right next to the suspect data columns, making it easier to compare for matches of repeating base pair sequences.

Activity Extensions

With the popularity of the CSI television shows, students may have some understanding of forensic evidence. Along these lines, have students investigate the creative tools, equipment and processes used to accurately collect and examine DNA evidence for crime, paternity and ancestry investigations.

What is your ancestry? Are we all related? With the advances in understanding DNA, and the availability of engineered collection and analysis tools, more and more people are aware of genetic genealogy. Have students investigate the National Geographic Society's Genographic Project — an anthropological study to map historical human migration patterns by collecting and analyzing DNA samples from hundreds of thousands of volunteers across five continents. See https://genographic.nationalgeographic.com/genographic/index.html

Activity Scaling

  • For lower grades, use fewer CODIS sites and suspects.
  • For upper grades, use more CODIS sites and suspects.

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References

Basic Biology of DNA. About Forensic DNA, President's DNA Initiative, USA.gov. Accessed February 24, 2009. (Glossary is source of some vocabulary definitions, with some adaptation) http://www.dna.gov/basics/biology/

Crime Lab FAQs. Crime Laboratory Division, Missouri State Highway Patrol. Accessed February 24, 2009. (scroll down for DNA analysis and profiling questions/answers) http://www.mshp.dps.mo.gov/MSHPWeb/PatrolDivisions/CLD/faqs.html

DNA Casework. Crime Laboratory Division, Missouri State Highway Patrol. Accessed February 24, 2009. http://www.mshp.dps.missouri.gov/MSHPWeb/PatrolDivisions/CLD/DNACasework/DNACasework.html

DNA Profiling. Crime Laboratory Division, Missouri State Highway Patrol. Accessed February 24, 2009. http://www.mshp.dps.missouri.gov/MSHPWeb/PatrolDivisions/CLD/DNAProfiling/DNAProfiling.html

How DNA Evidence Works. HowStuffWorks. Accessed February 24, 2009. http://science.howstuffworks.com/dna-evidence1.htm

Putting DNA to Work. Marian Koshland Science Museum of the National Academy of Sciences, The National Academies, Washington, DC. Accessed February 24, 2009. (Great DNA reference; topics include DNA and criminal justice; Catch a Criminal activity is inspiration for this activity) https://koshland-science-museum.org/

Copyright

© 2007 by Regents of the University of Colorado.

Contributors

Frank Burkholder; Malinda Schaefer Zarske; Denise W. Carlson

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: December 12, 2022

Hands-on Activity DNA Build

Quick Look

Grade Level: 6 (5-7)

Time Required: 45 minutes

Expendable Cost/Group: US $2.00

Group Size: 2

Activity Dependency: None

Quick Look

Grade Level:
6 (5 – 7)
Time Required:
45 minutes
Group Size:
2
Discuss this activity

TE Newsletter

Photo shows two students holding a gumdrop and toothpick creation shaped like a DNA double helix.
Students model DNA using gumdrops and toothpicks

Summary

Students reinforce their knowledge that DNA is the genetic material for all living things by modeling it using toothpicks and gumdrops that represent the four biochemicals (adenine, thiamine, guanine, and cytosine) that pair with each other in a specific pattern, making a double helix. They investigate specific DNA sequences that code for certain physical characteristics such as eye and hair color. Student teams trade DNA "strands" and de-code the genetic sequences to determine the physical characteristics (phenotype) displayed by the strands (genotype) from other groups. Students extend their knowledge to learn about DNA fingerprinting and recognizing DNA alterations that may result in genetic disorders.

Engineering Connection

Biomedical engineers study which specific DNA sequences code for certain characteristics as they investigate genetic disorders such as color blindness, Down syndrome, cystic fibrosis and hemophilia. Engineers develop technologies to recognize certain DNA mutations. Biomedical engineers study genes and DNA to develop technologies that could manipulate or replace genes that are damaged or missing. Gene therapy has many implications for the diagnosis, treatment and possibly prevention of human diseases such as cancer, cystic fibrosis and heart disease.

Learning Objectives

After this activity, students should be able to:

  • Explain that certain DNA sequences code for specific characteristics.
  • List several types of engineers and engineering technologies that rely on DNA sequences.
  • Investigate basic gene sequences to determine the genotype and phenotype of an individual.

Materials List

Each group needs:

  • toothpicks, ~25
  • multicolored gumdrops, ~30
  • paper or plastic plate, to work on so the table stays clean from loose sugar
  • 1 DNA color key (as found on the DNA Build Color Key; cut apart to create three color keys)
  • 1 DNA identity card (as found on the DNA Build Identity Key, cut apart to create 15 unique DNA identity cards)
  • blank sheet of paper, for coding notes and sketching
  • pencil

For the entire class to share:

Worksheets and Attachments

Visit [www.teachengineering.org/curriculum/print/cub_biomed_lesson09] to print or download.

Pre-Req Knowledge

An understanding that DNA is the genetic material for all living things.

Introduction/Motivation

We have all heard about DNA, but what exactly is DNA and why is it important to us? DNA stands for deoxyribonucleic acid and is made up of billions of biochemicals. DNA is the genetic material for all living things — this means that you, me, flowers, dogs, elephants and even viruses contain DNA. You can think of DNA as the "recipe" for living things — it provides the instructions for every part of the organism. In humans, 99.99% of our DNA is exactly the same as every other person's. Why is there a 0.01% difference? This small amount of DNA is what determines our physical differences such as eye color, hair color, height, etc. Even though our DNA is almost all the same, every single person (except for identical twins) has a unique DNA "recipe."

Where in our bodies is DNA located? DNA is stored in the nucleus of each cell where it is best protected from damage. Each nucleus contains 23 pairs (23 from your mom and 23 from your dad) of DNA, called chromosomes. This DNA is folded over and over into VERY small bundles — much too small for the human eye to see.

DNA is organized into shorter segments called genes. Think about a gummy candy worm as the entire strand of DNA, but each colored segment is a different gene. Genes are specific sequences of DNA that code for certain characteristics. The DNA sequence is called the genotype — this is the recipe — and the characteristics are called the phenotype — this is the cake!

DNA is made of four biochemicals called nucleotide bases (or just "bases"). Think of these as the ingredients in the recipe. They are: adenine, thymine, guanine and cytosine. To make things easier, people usually abbreviate these as A, T, G and C. These four bases pair with each other in a very specific way: A always pairs with T and G always pairs with C. One gene usually contains 10,000 to 15,000 base pairs!

Drawing shows circular stairway-shape with cross rungs made from pairs of adenine and thymine, or guanine and cytosine biochemicals.
DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.
copyright
Copyright © Michael Stroeck, US National Library of Medicine. http://ghr.nlm.nih.gov/handbook/basics/dna

Why is it important to understand genes and base pair sequences? Have you ever heard of color blindness, Down syndrome, cystic fibrosis or hemophilia? Well, biomedical engineers work with others in the scientific and medical fields to help improve health care and quality of life. They study DNA to help us understand genetic disorders like these. As engineers develop technologies to recognize certain DNA mutations and where they are located, they work with geneticists to diagnose, treat and prevent these disorders.

Genetic engineers study genes and DNA to understand things like DNA replication, cloning and genetically-modified organisms such as food and crops. Genetic engineers have helped us advance our crop technologies and make synthetic (artificial) insulin for people with diabetes.

DNA can also identify people — even better than fingerprints. DNA is found in all of our cells: hair, teeth, bones, blood and saliva. We can leave our DNA behind when we drink from a cup, use a toothbrush, shed hair or cut ourselves on something sharp. Because of this, DNA is used for "DNA fingerprinting" — or describing the unique DNA recipe for a person. Even 0.01% difference is enough to distinguish one person from another when it comes to collecting evidence from a crime scene.

Using DNA in a crime investigation does have its limitations. The probability of laboratory error or contamination — errors made when collecting and running the DNA samples — must be factored into the results. It is always best to consider DNA fingerprinting along with other evidence. Biomedical engineers create the tools, equipment and processes to accurately collect and examine DNA evidence for crime and paternity cases. They are always working to make the laboratory errors fewer and the machines for identifying the gene sequences more accurate.

Today, we are going to practice determining the phenotypes (physical characteristics) of persons from their DNA. We are going to work together to make models of human DNA and swap them with each other to decode. Like biomedical engineers, let's break down DNA gene sequences into individual traits to describe the people to which the DNA belongs.

Procedure

Background

Remind students that DNA is composed of four nucleotide bases: adenine (A), thymine (T), guanine (G) and cytosine (C). These four bases pair with each other in a very specific way: A always pairs with T and G always pairs with C.

Before the Activity

  • Gather materials and make photocopies or printouts (as described next).
  • For every three groups (of two students each), print one copy of the DNA Build Color Key; cut along the dotted lines to create three color keys from each sheet.
  • Print one copy of the DNA Build Identity Key and cut out the 15 DNA identity cards (one per group).
  • Create an overhead transparency of the DNA Build Identity Key and display it on an overhead projector.

With the Students: Part 1

  1. Divide the class into groups of two students each.
  2. Hand out supplies to each pair of students: 1 plate, ~25 toothpicks ~30 gumdrops, 1 DNA identity card and 1 color key.
  3. Explain that the color key contains the three-base genotypes that code for certain phenotypes (physical characteristics).
  4. Explain that the DNA identity cards contain the names and physical characteristics of various people, different for every team. This is the person's DNA that the team will construct. Remind students to keep this person's identity a secret from the other groups (for now).
  5. For each physical characteristic on the identity cards (phenotype), refer to the color key and have groups write down in columns the sequences of letters (genotypes, using A, T, G and C) for their persons. Then, have students write the corresponding base pairs in second columns. This is where the background knowledge above will come into play. A always pairs with T and G always pairs with C. (For example, if the genotype for brown eyes is TGG, you would use the color code for the gum drops to find the conjugate pairs of ACC.) The associated YouTube video is a great visual resource to show this example. 
  6. Allow enough time (~15-20 minutes) for teams to build the strand of DNA for their persons. For DNA building tips, see Figures 1 and 2 and the next section.

Three photos show hands placing three gumdrops on a toothpick, connecting the gumdrop sets with more toothpicks, and a completed ladder shape of two long strands of 15 gumdrops each.
Figure 1a-b-c. Students construct a gumdrop DNA strand.
copyright
Copyright © 2008 Megan Schroeder, ITL Program, University of Colorado at Boulder.

  1. Once all groups have completed building, have them trade DNA strands, and by working backwards from the strand only (no peeking at the identity cards), each group should determine whose DNA they have (by referring to the possible identities shown with the overhead projector). Students really enjoy this "decoding" part!
  2. Have students check with the original creator teams of the DNA strands to see if they determined the right DNA identities. Discuss with the class: How many groups were able to name the right identity for their DNA strands? What made decoding difficult?

Photo shows two students holding a twisted ladder-like creation made of gumdrops and toothpicks.
Figure 2. Students show off their completed gumdrop DNA double helix model.
copyright
Copyright © 2008 Megan Schroeder, ITL Program, University of Colorado at Boulder.

Suggested DNA Building Steps

It is easiest to construct the DNA strand by following these steps:

  1. While referring to the identity card and color key, write down in a column the base letters (A, T, G and C; genotype) and the corresponding base pairs in a second column for the first physical characteristic (phenotype).
  2. Next, build each "gene" in the first column of three bases by placing three gumdrops (of the correct colors) on one toothpick (see Figure 1a). Refer to the color key.
  3. Once all five "genes" from one column are built, repeat the process to build the corresponding base sequences from the second column of letters.
  4. Connect the base pairs by placing a toothpick between each of the three gumdrops — this creates five "ladders" for each gene (see Figure 1b).
  5. Now connect all the genes by sticking the end of the toothpicks with the gumdrops together. Be sure to keep the genes in the correct order and orientation (see Figure 1c).
  6. Finally, gently twist the entire strand to shape the double helix (see Figure 2)!

With the Students: Part 2

  1. Tell the students that they are biomedical engineers working with a city's police department. They have developed a technology that allows them to isolate several gene sequences in human DNA. The technology has helped them come up with the color keys that they used earlier (in Part 1).
  2. The police have several crime cases in which they need help finding a suspect. They would like to know the phenotype (physical characteristics) of the person from the DNA samples taken from blood and hair evidence. The students' task is to break down the gene sequences in the sample and identify some physical characteristics of the person. According to their color keys, what does the person look like? Have them draw preliminary sketches or descriptions of the persons on blank sheets of paper.
  • Sample DNA 1: TGGGCTTAAGGGATA (Answer: Brown eyes, blonde hair, right-handed, medium height, round nose.)
  • Sample DNA 2: TGCGTCTTAGAACAT (Answer: Hazel eyes, red hair, left-handed, short height, pointy nose.)
  • Sample DNA 3: TGGGTGTAAGGGGTA (Answer: Brown eyes, black hair, right-handed, medium height, long nose.)
  1. Conclude by leading a class discussion about biomedical engineering and genetic disorders, as described in the Assessment section. For this post-activity assessment, have students use their color keys to look at a few more DNA samples for indications of genetic disorders.

Vocabulary/Definitions

biomedical engineer: A person who blends traditional engineering techniques with the biological sciences and medicine to improve the quality of human health and life. Biomedical engineers design artificial body parts, medical devices, diagnostic tools, and medical treatment methods.

chromosome: A group of genes; humans have 23 pairs of chromosomes (46 total) in a cell nucleus.

deoxyribonucleic acid: abbreviated DNA. The genetic material for all living things; located in the cell nucleus.

gene: A section of DNA that carries information to determine characteristics or traits.

genotype: The specific sequence of DNA in a gene.

hazel: Light golden-brown or yellowish-brown color (as the color of a hazelnut).

model: (noun) A representation of something for imitation, comparison or analysis, sometimes on a different scale. (verb) To make something to help learn about something else that cannot be directly observed or experimented upon.

nucleotide bases: The parts of RNA and DNA involved in pairing; they include cytosine, guanine, adenine, thymine (DNA) and uracil (RNA), abbreviated as C, G, A, T and U. They are usually simply called bases in genetics. Also called base pairs or bases.

phenotype: The outward, physical characteristic(s) expressed by a gene sequence.

Assessment

Pre-Activity Assessment

Discussion Questions: Ask the students and discuss as a class.

  • Why do we look like our parents? (Answer: Each of us receives genetic information from each of our parents.)
  • Where in our bodies is genetic information stored? (Answer: All genetic information is in our DNA, located in the nucleus of each cell.)

Activity Embedded Assessment

Question/Answer: While students are building their DNA strands, ask them the following questions:

  • What is DNA? (Answer: DNA is the genetic material for all living things.)
  • What is a gene? (Answer: A gene is a segment of DNA that codes for a specific trait.)
  • Is there a way to have different characteristics with the same DNA sequence? (Answer: No, DNA sequencing is unique for each characteristic.)
  • What is DNA fingerprinting? (Answer: DNA fingerprinting is describing a person using DNA evidence from a biological sample, such as blood, saliva, tissue or hair.)
  • Do all humans have the same DNA? Explain. (Answer: No, humans share about 99.99% of DNA. Only identical twins share 100% of their DNA).
  • What type of engineer would work with DNA and genes? (Answer: A biomedical engineer.)
  • How are engineers involved in DNA and gene sequencing? (Answer: Biomedical engineers study which specific DNA sequences code for certain characteristics in order to recognize genetic disorders such as color blindness, Down syndrome, cystic fibrosis and hemophilia. Engineers design technologies that recognize certain DNA mutations and work with geneticists to diagnose and prevent the disorders.)

Post-Activity Assessment

Biomedical Engineering and Genetic Disorders Discussion: Most genetic disorders are associated with an alteration of DNA. For example, color blindness can be associated with a single mutation (change) on any of 19 different chromosomes and multiple different genes. These genetic disorders can be either numerical or structural. Numerical disorders occur when a DNA chromosome is either missing or has an extra copy. For example, Down syndrome is an example in which three copies of a DNA chromosome exist, instead of two. Structural disorders occur when a portion of a DNA chromosome is missing or replicated or moved to the wrong place. Have students discuss how an engineer might be able to develop technologies that look for specific gene changes or mutations in DNA. Using the color key, which of the following DNA samples might have a genetic disorder? What is the alteration? (Note: None of the following examples result in real disorders, but they each illustrate a type of change in the gene sequence of the DNA piece.)

  • AGGAGGGCCTAAGGGGTA (Answer: Duplication of the AGG gene.)
  • TGGGCTGTTATA (Answer: Deletion of a gene.)
  • TGCGTGGTATAAGGG (Answer: Gene in the wrong place. This translocation is usually seen when one chromosome attaches to an entirely different chromosome, or portions of two different chromosomes have been exchanged.)

Troubleshooting Tips

Groups may need to trade with other groups from their given gumdrop supply, as the gumdrop colors are different on each color key.

When connecting all the genes together, be sure to keep the genes in the correct order and orientation, or else they won't be able to be decoded by another team.

Activity Extensions

Have students research a specific genetic disorder and write a one-page summary about it, including a description of which chromosome is affected and the associated mutation. Examples include Down syndrome, color blindness, hemophilia and cystic fibrosis.

Activity Scaling

  • For lower grades, it may help to build one DNA strand as a class before students build on their own. Shorten the activity by constructing only two or three of the five characteristics (for example, just hair and eye color).

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References

About R&D - Research & Development. Updated November 27, 2008. GlaxoSmithKline plc. www.gsk.com 

Bachor, Kevin. Fun Facts (about DNA). The Best Detergent for Plentiful DNA Extraction, Cirque du Soleil, Ecole Nationale de Cirque, 2006 Canada Wide Virtual Science Fair. http://www.virtualsciencefair.org/2006/bach6k2/Funfacts.htm 

Copyright

© 2007 by Regents of the University of Colorado.

Contributors

Megan Schroeder; Malinda Schaefer Zarske; Janet Yowell; Denise W. Carlson

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: August 30, 2024