Constructing a Cladogram
Evolution & Amino Acid Sequences
A cladogram is a diagram that shows the evolutionary relationships between selected animals. The
closer the two organisms are on the cladogram, the more recently they shared a common ancestor.
Cytochrome-C is an enzyme found in virtually all organisms’ mitochondria. It is needed for the
release of energy from food (cellular respiration). The amino acid sequences in this protein are compared
for several different animals, and the number of differences found can be used to infer an evolutionary
relationship between them.
In this activity, this data will be compared using the cladogram below with the cladogram you will
construct using the amino acid sequences that create the protein, Cytochrome-C.
How to read a cladogram:
The cladogram below show the relationship of selected animals based on their shared anatomical features.
For example, out of seven key traits, all of these animals have a dorsal nerve chord & notochord, but only
humans, monkeys, and kangaroos have mammary glands.
Foramen Magnum forward & Short
Paired appendages & spinal column
Dorsal Nerve chord & notochord
You will now construct another cladogram using the SAME organisms on the cladogram above. First,
use the amino acid sequence chart attached to determine the number of differences in their amino
acids sequences for this one protein, Cytochrome-C. Make a table to record your data. Head the two
columns: Species and Number of Differences. For each organism, count the number of differences in
the amino acid sequence as compared to a HUMAN. List them on your table. Next, construct your
cladogram. Note: You will write your number of differences on your constructed cladogram replacing
the place where the anatomical structures are in the cladogram above after you figure out the
correct order to place the animals. Create your table and cladogram on the back of this
2. Compare the first cladogram (Anatomical Differences) that was provided on the first sheet of this
activity to the cladogram you created. What is the relationship between the animals with regards to
how they are arranged?
3. Hypothetically, if 3rd cladogram was created comparing the amino acid sequences of these same
animals of another protein (not Cytochrome-C) and the animals were placed in the same order on this
3rd cladogram, as they are in the Anatomical Differences and Cytochrome-C cladograms, what could
4. Chickens and turkeys are both birds and have identical Cytochrome-C amino acid sequences. Explain
how these two species could have identical sequences and yet be different species.
5. Neurospora (bread mold) and Saccharomycetes (baker’s yeast) are both fungi. Chickens and turkeys
are both birds. The differences in amino acid sequences for Cytochrome-C between these fungi,
however, are greater than that between these birds. What can you say about the inferred
evolutionary relationships between the two birds compared to the relationship between the two fungi?
Explain your reasoning. Use the term molecular clock in you answer.
6. What are the 6 evidences of evolution? How is biochemistry different than the other 5 evidences?