Biology Unit 4: Evolution
Analyzing Amino Acid Sequences Lab
Name ________________________________
MWF Teacher ____________ MWF Hour ___
Introduction.
During today’s activity, we will explore the evolutionary evidence provided by Molecular Biology. As
you learned during Unit 2 and 3, DNA is our blueprint for life. A DNA strand is long chain of
nucleotides combined together in a sequence that is unique to every living thing. DNA controls the
production of proteins. Proteins, for example, that make up your muscles, determine your eye color,
and control the clotting of your blood. Hopefully you also remember that proteins are simply chains
of amino acids linked together end to end. Ultimately, the sequence of our DNA determines the
sequence of amino acids making up the proteins in our body. So, if we compare the amino acid
sequences of different living things, we can determine how closely related these organisms might be.
Pre-Lab.
1. Explain how the amino acid sequence of an organism can show it’s relatedness to another
organism.
Procedure.
1. Find the human, rhesus monkey, kangaroo, snapping turtle, bullfrog, and tuna on the “Amino
Acid Sequence…From 20 Different Species Chart and underline them.
2. Compare the human amino acid sequence with each of these five animals by counting the
number of times an amino acid in that animal is different from the amino acid in that same
position of the human sequence. For example, the number of differences between the
human and dog amino acid sequences is 10. Note also that Page 2 is a continuation of Page
1. So, you should add the two pages together to get the total number of differences.
3. Complete the chart below.
Animal
Differences b/w
Animal & Human
Sequences
Bullfrog
Tuna
Kangaroo
Rhesus
Monkey
Snapping
Turtle
4. The diagram below is called a cladogram. It shows the relationship of selected ape species to
one another. Find the main line of the cladogram ending in human. The lines branching off
(ending in different species of primates) demonstrate how closely (or not closely) related an
organism is to humans. As an example, this cladogram shows that chimpanzees, because of
their location along the main line, are more closely related to humans than orangutans.
5. Using the data you have gathered about amino acid sequences, complete the cladogram
below. Humans have been placed at the end of the cladogram. Write each of the five
animals you analyzed above the five remaining arrows. Make sure they are in the appropriate
locations. In the hexagons below each arrow, write the number of amino acid differences
you found between the animal and a human.
Humans
Analysis & Conclusions. Answer each question completely.
1. In two or three sentences, summarize the information found in your cladogram. What general
pattern(s) does it show?
2. If you were able to compare the amino acid sequences of a duck and a chicken, you would
find that there are three amino acid differences. How does the human-monkey relationship
compare to the duck-chicken relationship?
3. On Day 1 of the Evolution Unit, you placed yourself on the Spectrum Of Beliefs. What would
your school of thought say about this DNA/Amino Acid Evidence? You may need to do some
research on the internet!