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Two 45-minute class periods
NOTE: Students should be acquainted with protein synthesis,
in particular the translation process (incorporation of amino
acids into polypeptides) prior to participation in this unit.
The genetic code carries the instructions
for production of amino acid chains (proteins or polypeptide chains).
On occasion, a gene is altered— this may result from an error
in copying during replication or could result from damage to a
gene. Such a change, known as a mutation, could result in changes
in the recipe for a protein or group of proteins. While alteration
of a chromosome can result in dramatic, observable changes, in
this unit, point mutations (mutations affecting a single
gene) and the implications of the affect single genes can have
on development of characteristics are considered.
Through the activities in this lesson, students will become familiar
with the basic types of point mutation and the impacts each might
have on the amino acid sequence of a protein and hence upon the
characteristics of individuals exhibiting these mutations. After
examining the web sites and video clips and participating in class
discussion of mutations, students will “translate” mRNA
codons to determine the amino acid sequence in a polypeptide chain
of an origami whale. After translating the “wild type”
sequence, students will translate four sequences each exhibiting
a mutation, translate each sequence, and relate the changes in
the sequences to alterations in the protein structure (paper folds)
in the origami whales.
:
Biology
Students will be able to:
• Discuss the relationships among DNA, mRNA, mutations, and
protein synthesis
• Define and be able to identify: point mutation, Missense
mutation, nonsense mutation, silent mutation, frame-shift mutations
(insertion and deletion)
• “Translate” amino acid sequences
• Infer the general affect particular point mutations might
have on synthesis of a polypeptide chain
• Model (through use of an origami whale) and discuss possible
implications of mutations with regard to point mutations
National Science Education Standards
http://bob.nap.edu/html/nses/html
Content Standard C:
The Cell
Biological evolution
Louisiana Science Framework:
State Standards for Curriculum Development http://www.doe.state.la.us/doe/assessment/standards/SCIENCE.pdf
LS-H-B1: Explaining the relationship among chromosomes,
DNA, genes, RNA, and proteins
LS-H-C2: Recognizing the evidence for evolution
LS-H-C3: Discussing the patterns, mechanisms, and rate
of evolution
Video clips:
1. Learning and Teaching Evolution Evolving Ideas: Videos
for Students
Segment 5-Did Humans Evolve?
(Learning and Teaching Evolution, a compilation of 7 video clips
for students and case study videos for teachers is a part of the
PBS Evolution project. A VHS cassette of these clips (taken from
the 8 hour series) is available for purchase from WGBH Boston at
1-800-949-8670 for $19.95. Streamlined versions of the videos are
available at the website: http://www.pbs.org/evolution)
2. Evolution: A Journey into Where
We’re From and Where We’re Headed
Great Transformations
The segment to be viewed opens with a view of flies being observed
via a microscope and with the phrase, “By the 1940s, scientists
working with fruit flies…” (This is approximately 37½
minutes into the video.) It ends about 6 minutes later with “If
one of these genes turned on in the wrong place, striking changes
in the body could take place. The visual is a multicolored fly
whose body parts are colored coordinated to the gene coding for
that trait.
Web Sites:
Mutation and Protein Synthesis:
Biology ClassONline
http://www.mccsc.edu/~jracy/A3231.html
This includes biology course class notes. The material is written
on a level appropriate for most high school students.
Evolution:
Evolution Project
http://www.pbs.org/evolution
This site is packed with interactive features that allow users
to test the evolutionary principals in action. It includes inquiry-based,
teacher-assigned lessons for students, streamlined versions of
the Videos for Students: Evolving Ideas, and direct web access
to hundreds of other multimedia evolution resources.
Evolution –Teacher’s Guide Web
Resources: Unit 5-Chromosome Clues
http://www.pbs.org/evolution
This activity uses photos of real chromosomes to compare chromosomes
from three species and to introduce the concept of chromosome
inversion.
mRNA Codons and Amino Acid Sequences
http://www.ship.edu/~bmushe/codons.html
Chart listing the amino acids coded by each mRNA codon.
Whales (optional):
Introduction to Cetacea
http://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html
This site discusses general characteristics of whales and dolphins
and evolution of the cetaceans.
For each student:
• Focus for Video Interaction 1 (Changes in the Genetic Code)
HTML PDF
• Focus for Video Interaction 2 (Whale of a Change)
HTML PDF
• Changes in Gene Sequence worksheet (Culminating Activity)
HTML PDF
For each student or small group of students:
• One copy of the origami whale worksheet
HTML PDF
• One copy of the whale origami instructions (with picture
instructions)
HTML PDF
1. Prior to teaching the unit, bookmark the Web sites used
(as reference).
2. Prepare copies of the Focus for Video Interaction and
Changes in a Gene Sequence worksheets and the origami whale instructions.
3. CUE video segments.
Students should be acquainted with DNA, RNA and protein synthesis,
including the translation process (incorporation of amino acids
into polypeptides) prior to participation in this unit. Biology
texts generally include a chart which students can use in “reading”
the codons and determining amino acid placement in a polypeptide
(protein) chain.
1. a. Provide a FOCUS FOR MEDIA INTERACTION by instructing
students to listen closely for new terms and their meanings.
START video clip 1.
b. PAUSE: after the narrator says, “you will arrive
at the common ancestor we share with today’s apes.”
Ask the students to differentiate in their own words the difference
between related to and descended from.
c. RESUME the video.
d. PAUSE when the narrator says, “we can establish
how closely related they are related one to another.” Discuss
with students the following question: What do we learn by comparing
the DNA sequences of organisms. Instruct the students to
• listen for any comparisons made between humans and other
animals and for any identification of common ancestors and humans
in the next section of the program
• study what is meant by making note of spelling changes.
e. RESUME the video and play until the end of segment 5.
At the conclusion ask the students the importance of spelling
changes. Have the students discuss Focus of Video Interaction
problems 1 and 2.
2. Discuss the concept of mutations. Introduce the concept
of point mutations and have students complete the Class Notes
section of the first worksheet. If available biology texts include
a discussion on point mutations, assign students to read the section.
A point mutation is a change in the genetic material that affects
only one gene. Point mutations are frequently classified as:
• Silent mutations in which the change in the codon
does not result in a change in the amino acid coded for and, therefore
no change occurs in the protein chain. For example, CUU, CUC,
CUA and CUG all code for leucine; therefore, a change in the third
position of the codon would not affect the amino acid in a chain.
• Nonsense mutations are those in which the affected
codon no longer codes for an amino acid but for a “stop”
or “termination “ codon. (For example, if UGC is altered
to UGA) This will result in incomplete production of the polypeptide
chain.
• Missense mutations are those in which the change
results in a change in an amino acid added to the sequence. This
change could result in a minor change in the protein or in a protein
with dramatically different characteristics. (For example, the
difference in the structure of “normal” hemoglobin and
that of hemoglobin resulting in sickle-cell anemia is a difference
of one amino acid in each of two matching strands of the molecule
composed of approximately 2800 amino acids.)
In addition, changes in genetic sequences can result from changes
classified as frame-shift mutations.
• Frame-shift mutations are those in which nucleotides
are inserted or deleted (as a result of an error in copying or
damage to the chromosome). This modifies the previous grouping
of nucleotides in the codons and causes a new sequence of codons
to be read. (For example. If the” original” code read
AUG GGA AGA CCG… and the first nucleotide in the second codon
were deleted, the new code would be AUG GAA GAC CG… which
would produce a different protein chain.
Chromosome inversions could also be introduced at this time through
use of the evolution Teacher’s Guide Web Resource
activity, Chromosome Clues.
3. a. Provide a FOCUS FOR MEDIA INTERACTION
by asking students to consider the shape and composition of DNA
and to listen to identify how researchers would trigger developmental
change.
b. START the second video clip.
c. PAUSE after the words “Scientists were just beginning
to grasp the fact that DNA itself was made up of up Segments.”
Prompt the students to report on the important terms and allow
time for students to share comments and ask questions. Provide
wait time before answering to allow students to reflect on one
another’s questions and offer their own answers.
d. RESUME play and run until the end of the clip with “If
one of these genes turned on in the wrong place, striking changes
in the body could take place. The visual is a multicolored -fly
whose body parts are colored coordinated to the gene coding for
that trait. After viewing the video, have students discuss the
meaning of the statement, “If one of the genes turned on
in the wrong place, striking changes to the body could take place”,
and relate the quote to point mutations.
4. Distribute the CHANGES IN A GENE SEQUENCE. Tell students
that researches have noted differences in the codon sequences
for a particular origami whale protein. Have them use textbook
copies of the mRNA/amino acid tables to determine the sequence
of amino acids coded for by each of the chains illustrated. If
the table is not available in class texts, one is available at
Web site,
http://www.ship.edu/~bmushe/codons.html.
5. Have students label each of the mutated sequences by
the type of mutation it illustrates. It is not necessary to review
each amino acid in each of the chains unless you wish to do so
but do have students infer possible effects of the mutations on
protein production.
Type 2 illustrates a silent mutation, type 3 a nonsense mutation,
type 4 is a frame-shift resulting from a deletion and type 5 is
an example of a frame-shift due to an insertion.
6. Guide students through the experimental design portion
of the lab activity.
Problem: While these may vary, a possible problem might
be, “What affect do various point mutations have on origami
whale development?”
Hypothesis and justification: Have students develop and
justify their hypotheses and discuss these with the class.
Independent Variable: the mutation
Dependent Variable: changes in the amino acid sequence
Control Group: the “wild type” sequence
Collect data (make, compare, and discuss the whale variations)
Assign each student lab group one or more of the whale gene sequence
variations. Following instructions on the “Whale” sheet,
they should make compare, and discuss the origami whale variation(s)
assigned)
Draw conclusions based on the data collected. Answers may
vary but will make for interesting class discussions and may serve
to identify student misconceptions and to introduce concepts of
adaptation and natural selection (This may be a good time to discuss
adaptation and to stress that adaptation occurs within populations
not individuals).
Mathematics: Research and calculate mutation rates in bacteria
and relate these to the rates at which drug resistance develops
in these organisms.
Art and Science: Relate the techniques of paper folding
to protein synthesis. Discuss mutations and evolution in terms
of the history of origami art forms.
• Focus for Video Interaction 1 (Changes in the Genetic Code)
HTML PDF
• Focus for Video Interaction 2 (Whale of a Change)
HTML PDF
• Changes in Gene Sequence worksheet
HTML PDF
• Whale origami variations sheets
HTML PDF
• Whale origami instruction sheet (with diagram instructions)
HTML PDF
• Invite a medical researcher to discuss mutation rate in
pathogenic organisms and discuss their affect on medical treatment.
• Invite a wildlife biologist to discuss variations within
a species of organism and the implications of these on survival
rate of the species.
• Visit an arboretum, forest research center, or horticultural
research lab. Observe science at work utilizing mutations to create
“improved” strains of organism (for example, grafting
of seedless orange tree boughs to hardy rootstock)
