COMPARING DNA TO DETERMINE EVOLUTIONARY
RELATIONSHIPS
Your group will be making strands of primate DNA and then comparing
those strands to determine how closely related the primates are. DNA makes
up the genetic code from which all organisms are built. This code is written
with a four letter alphabet of chemicals called bases, these are: (A)adenine,
(G)guanine, (T)thymine, and (C)cytosine. The order of these letters in the
genetic code determine what type of organism is made.
PROCEDURES
Each group member must first construct their assigned strand of DNA. You will be using
colored beads to represent the different bases:
green = adenine (A)
red = guanine (G)
blue = thymine (T)
orange = cytosine (C)
Build your DNA strand by connecting colored beads in the proper sequence according to
specifications listed for each group member. When you have completed your strand,
place it on a piece of paper and label “Position 1” and “Position 20” of your strand as
well as what type of primate your DNA is from.
Group member 1
Build a strand of DNA that has the following sequence and label it “human DNA”:
Position 1
Position 20
A-G-G-C-A-T-A-A-A-C-C-A-A-C-C-G-A-T-T-A
Group member 2
Build a strand of DNA that has the following sequence and label it “chimpanzee DNA”:
Position 1
Position 20
A-G-G-C-C-C-C-T-T-C-C-A-A-C-C-G-A-T-T-A
Group member 3
Build a strand of DNA that has the following sequence and label it “gorilla DNA”
Position 1
Position 20
A-G-G-C-C-C-C-T-T-C-C-A-A-C-C-A-G-G-C-C
Group member 4
Build a strand of DNA that has the following sequence and label it “common ancestor
DNA”:
Position 1
Position 20
A-G-G-C-C-G-G-C-T-C-C-A-A-C-C-A-G-G-C-C

Copy the following tables in your journal.
DATA FOR HUMAN DNA
Human DNA compared to:
Number of matches
Unmatched bases
Chimpanzee DNA
Gorilla DNA


Compare the human DNA to the chimpanzee DNA by matching the strands base by
base. Count the number of bases that are not the same and record this number in your
data table
Repeat the previous step with the human DNA and the gorilla DNA.
DATA FOR COMMON ANCESTOR DNA
Common ancestor DNA
Number of matches
Unmatched bases
compared to:
Human DNA
Chimpanzee DNA
Gorilla DNA

Compare the common ancestor DNA to all three samples of DNA (gorilla, human,
and chimpanzee), one sample at a time. Record the data in your table.
ANALYSIS
Using the data you collected answer the following questions in complete
sentences.
1. How do the gorilla DNA and the chimpanzee DNA compare with the human DNA?
2. What do these data suggest about the relationship between humans, gorillas, and
chimpanzees?
3. Which of the hypotheses for evolutionary relationships do your data best support?
Explain why!
4. Based on the hypothesis that your data best supported, which of the following
statements is most accurate? Explain your answer in a short paragraph.
A. Humans and apes have a common ancestor
B. Humans have evolved from apes.