Page 1
SBI 3U
Panayiotou
Inquiry Activity Comparing Chromosomes
Major Lab
Question What can the analysis of human and chimpanzee chromosomes tell us about their potential
evolutionary relationship?
Crime scene specialists use bullet markings to identify which gun was used in a crime. Bullets fired from a
specific gun all have the same bullet markings. The specialists fire guns they suspect were used in a crime
and compare the bullet markings to those on the bullets found at the crime scene.
TCH: bullet marks in image file]
The number of chromosomes and the banding patterns on each chromosome are unique to a species, just
as bullet markings are to a gun. The figure below shows the banding pattern on human chromosome 1..
[CATCH: image of chromosome 1 banding pattern in image bank]
Caption: Chromosomes that contain the genetic code are found in the nucleus. The image above shows
how a particular chromosome has light and dark banding patterns. The light regions are coding DNA.
The dark bands on the chromosome are thought to be non-coding DNA while the light bands contain DNA
that codes for amino acids, the building blocks of proteins. Recall that the place where a chromosome
narrows is called the centromere. This is where the spindle fibres attach to pull the chromosomes to
opposite sides of the cell during mitosis. Comparing the banding patterns on similar chromosomes from
different species can give us insight into the organisms' evolutionary relationships.
SBI 3U
Panayiotou
Page 2
Question
How does comparing chromosomes from primates help establish evolutionary relationships?
Materials & Equipment



BLM of chimpanzee and human chromosomes
scissors
tape or glue
Hypothesis
1. Create a hypothesis about how the number of human chromosomes compares to the number of
chimpanzee chromosomes. (1)
2. Create a hypothesis about human banding patterns compared to chimpanzee banding patterns as well
as the lengths of each chromosome. (1)
Procedure
1. Match the chimpanzee chromosomes to similar human chromosomes as much as possible.
3. Once you are confident with all your matches, take a picture or sketch the chimpanzee chromosomes
next to their matching human chromosomes.
Observations
1. Photo evidence or sketch of matching pairs of chromosomes. (2)
2. Compare in detail human and chimpanzee chromosomes in terms of (3)
a) the number of chromosomes,
b) similarities and differences in banding patterns, and
c) the sizes of chromosomes.
Analyzing and Interpreting
3. How do your answers to (2) compare to your hypotheses? (1)
4. Do you think the difference in number of chromosomes between these two species represent a
significant difference? Explain. (2)
5. Examine the human chromosome 4 and its matched chimpanzee chromosome. (2)
a) How are the two chromosomes different? Be specific.
b) Are there any other chromosomes that exhibit this difference? Identify two specific examples.
SBI 3U
Panayiotou
Page 3
6. Do you think the different arrangement of DNA in chromosome 4 makes a difference in proteins that the
two organisms make? Explain. (2)
7. a) What is the difference in chromosome 7 between the two species? (1)
b) Does this affect the overall quantity of coding DNA to make a difference in the animals? Explain. (2)
8. Examine the chromosomes below of human, chimpanzee, gorillas and orang-utans. Write a brief
paragraph outlining the differences and similarities. Which differences do you think are most significant to
the uniqueness of each organism? Explain why. (3)
[CATCH: image of 4 comparisons from image file]
CAPTION; Human (H)chimpanzee ©, gorilla (G), and orang-utan (O) chromosomes are compared above.
9. Examine the evolutionary relationships shown below. Orangutans, chimpanzees, and gorillas all have 48
(24 pairs) of chromosomes while humans have 46 (23 pairs). There are two hypotheses to explain how this
has happened.
(a) Fusion Hypothesis: The common ancestor for chimps and humans had two smaller chromosomes that
fused together to form one large chromosome.
(b) Fission Hypothesis: The common ancestor had one large chromosome that split into two smaller
chromosomes.
A cladogram shows the evolutionary relationships between species. Looking at the image below, which
hypothesis above likely happened? Explain. (2)
SBI 3U
Panayiotou
Page 4
[CATCH: image of cladogram]
10. To determine which hypothesis was more likely, scientists looked at the telomere patterns. Telomeres
are repetitive sequences of nucleotides at both ends of a chromosome. For example, they could have the
sequence “TACCGATCC” repeated several times. Using this information, what evidence should you see on
chromosome 2 if fusion occurred? Explain your answer. (2)
Forming Conclusions
12. Summarize how evolutionary relationships can be established using the DNA analysis techniques used
in this lab. (1)
TOTAL VALUE: 25 MARKS