DNA BUILD
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.
Today you are going to reinforce your knowledge that DNA is the genetic material for all living things by modeling
it using toothpicks and mini-marshmallows that represent the four biochemicals (adenine, thiamine, guanine, and
cytosine) that pair with each other in a specific pattern, making a double helix. You will investigate specific DNA
sequences that code for certain physical characteristics such as eye and hair color. Teams will then trade DNA "strands"
and de-code the genetic sequences to determine the physical characteristics (phenotype) displayed by the strands
(genotype) from other groups. You will use this knowledge to decipher information about DNA.
Like biomedical engineers, you will break down DNA gene sequences into individual traits to describe the people
to which the DNA belongs.
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
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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
1 DNA identity card
blank sheet of paper, for coding notes and sketching
pencil
Helpful Vocabulary
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.
DNA:
The genetic material for all living things; located in the cell nucleus. Short for deoxyribonucleic
acid.
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
The parts of RNA and DNA involved in pairing; they include cytosine, guanine, adenine,
bases:
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.
Figure 1a-b-c. Students construct a gumdrop DNA strand.
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Figure 2. Students show off their completed gumdrop DNA double helix model.
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Procedure
Part 1:
It is easiest to construct the DNA strand by following these steps:
 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).
 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.
 Once all five "genes" from one column are built, repeat the process to build the corresponding base sequences
from the second column of letters.
 Connect the base pairs by placing a toothpick between each of the three gumdrops — this creates five "ladders"
for each gene (see Figure 1b).
 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).
 Finally, gently twist the entire strand to shape the double helix (see Figure 2)!
 Once you have completed your strand trade it with another group and then try to figure out the identity of their
person based on the strand of DNA.
Part 2:
Now imagine you are a 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 you used earlier (in Part 1).
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. You are to
obtain a strand of DNA from the teacher, then 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? Once you have determined
the identity of the person draw a beginning sketch of what your person looks like.
Analysis Questions:
1. What is DNA?
2. What is a gene?
3. Is there a way to have different characteristics with the same DNA sequence?
4. What is DNA fingerprinting?
5. Do all humans have the same DNA? Explain.
6. What type of engineer would work with DNA and genes?
7. How are engineers involved in DNA and gene sequencing?