Download DNA and Protein Synthesis – Grade 10

DNA and Protein Synthesis – Grade 10
Ohio Standards
Connection:
Life Sciences
Benchmark C
Explain the genetic
mechanisms and molecular
basis of inheritance.
Indicator 5
Illustrate the relationship of
the structure and function
of DNA to protein
synthesis and the
characteristics of an
organism.
Lesson Summary:
In this lesson, students will understand the role of DNA in
protein synthesis. The relationship between protein
synthesis and the characteristics of an organism will be
analyzed through an activity that allows students to model
the process.
Estimated Time Duration: 75 minutes
Commentary:
This lesson provides students with the opportunity to use
kinesthetic activity to deepen their understanding of how
DNA is related to protein synthesis which builds and carries
out the functions of living organisms.
This lesson was field tested by teachers across the state of
Ohio. One teacher commented:
• “It is simple, but effective. I particularly like the tips
that are included.”
Pre-Assessment:
• Group students in teams of two.
• Distribute three by five cards with the following steps of
transcription and translation posted on them:
• DNA is unwound;
• mRNA is made;
• mRNA matures;
• mRNA attaches at ribosome;
• tRNA matches codon;
• Peptide bonds are formed;
• Stop codon is read;
• mRNA and protein are released.
• Scramble the cards when distributing them to students.
• Instruct the students to put these steps in the correct order.
A timer can be used for this activity.
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DNA and Protein Synthesis – Grade 10
Scoring Guidelines:
The correct sequence is as follows:
• DNA is unwound;
• mRNA is made;
• mRNA matures;
• mRNA attaches at ribosome;
• tRNA matches codon;
• Peptide bonds are formed;
• Stop codon is read;
• mRNA and protein are released.
Observe students and make notes of their conversation to determine their level of
understanding. Use this information to adjust instructional procedures where necessary.
Post Assessment:
• Provide each student with the following DNA sequence:
TAC GCT TTC CGA TGG CTA TGA (parent strand).
• Instruct the students to record the complementary DNA that would form during
replication (complementary strand).
• Next, direct the students to record the resulting mRNA sequence that would be formed.
• Then, explain to the students that a mutation will occur in the parent strand of DNA
sequence. Instruct the students to change the 18th letter in the sequence from “A” to “G.”
• Then, ask the students the following questions:
1. What initiates and terminates mRNA coding?
2. If one base in the DNA is changed, describe what may happen to the protein that is
formed.
3. When DNA changes, what does it do to the protein that is made?
4. Describe how this change may or may not affect the characteristics of the organism.
Scoring Guidelines:
1. The amino acid sequence “AUG” is the start codon. The mRNA begins coding at that
point. Three specific amino acids (TAA, TAG and TGA) inform the mRNA to stop
reading the code and the amino acid chain is released.
2. If one base is changed, the amino acid that is coded for may be changed, changing the
protein that is formed. This may or may not be an issue because many combinations of
bases in a codon can code for the same amino acid. If this is the case, no change is made
to the corresponding amino acid and the protein remains the same. If the base change
alters the amino acid it is coding for, then the protein may be altered and the resulting
protein may be changed which may initiate a change in the structure and the function of
an organism. If the charges on the amino acid do not change, the tertiary structure of the
protein does not change.
3. When DNA changes, the protein that is made during transcription and translation may be
changed because of a change in the amino acid sequence. The rationale is the same as in
the previous question.
4. Changes in the sequence of amino acids may change the shape or size of a protein and
therefore may result in a change of the function or shape of the organism.
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DNA and Protein Synthesis – Grade 10
Instructional Procedures:
Student Engagement
1. Ask students the following questions for a journal entry:
a. How does your DNA relate to your physical characteristics such as eye color or the
ability to roll your tongue?
2. Prepare the following materials:
a. Make a banner with the following DNA sequence:
AAAAA TAC GAT AGC TTT CCG ATG GCT ATT GGGGG.
b. Make one card with the letter “T” to be used to cover up the “G” in the base triplet
AGT in the banner.
c. Make eight cards (approximately four by six) with one codon per card written in
large letters. AUG, CUA, UCG, AAA, GGC, UAC, CGA, and UAA.
d. Make at least eight, 4x6 cards with the following tRNA anti-codons and amino acid
names written in large letters. Put one tRNA anticodon / amino acid pair to a card.
AUG / Start; CUA / leucine; UCG / serine, AAA / lysine, GGC / glycine; UAC /
tyrosine, CGA / arganine, and UAA / Stop. Additional cards with appropriate tRNA
anti-codon/amino acid combinations should also be made so that all students will
have a card with either an mRNA codon or a tRNA anti-codon/amino acid.
3. Instruct students to work with a partner. Pass out one copy of Attachment A, Amino Acid
Codon Table, or a table of your choosing, to each pair of students. At least eight students
will be needed for this activity. Indicate to students that in this activity the class will be
building a protein. Briefly discuss how an organism needs and uses proteins (muscle, cell
structure, collagen in skin, hormones, etc.). Explain that the amino acids used to build
those proteins come from food or may already be present in the organism.
4. Show the DNA strand banner with the following base sequence:
AAAAA TAC GAT AGC TTT CCG ATG GCT ATT GGGGG.
Instructional Tip:
• The repeating A’s and the repeating G’s are used here to indicate stretches of DNA
between genes and therefore not transcribed into mRNA. In addition, the activity is
simplified from a natural system in that there are no introns to remove from the
transcribed mRNA before the mRNA is matured and used at the ribosome for translation
into a protein. The resulting mRNA sequence then reads:
AUG CUA UCG AAA GGC UAC CGA UAA.
5. Instruct the student pairs to record the complementary DNA sequence that would form
during replication.
Answer: TTTTT ATG CTA TCG AAA GGC TAC CGA TAA CCCCC.
6. Instruct the student pairs to record what the mRNA base sequence would be if the DNA
strand on the banner was being used as a mRNA template between the repeating A’s on
the left and the repeating G’s on the right.
7. Randomly pass out the necessary eight codon and eight tRNA anti-codon cards to the
students. From the remaining students, pick one student to be the rRNA. Distribute the
anti-codon cards to all remaining students. Each student should have a card.
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DNA and Protein Synthesis – Grade 10
8. Have the students with the mRNA codon cards arrange themselves in the appropriate
order and hold hands (or hold ends of a short rope) to show a bond as determined by the
DNA sequence on the banner. The line formed is then the full mRNA strand.
9. Have the student that is the mRNA start codon (AUG) find and go to the student that is
the rRNA. Then have the rRNA student direct the appropriate tRNA to align with the
mRNA codon. Have each tRNA/amino acid student arrange themselves according to the
mRNA sequence to form the developing protein until a stop codon is reached. Have the
rRNA student then release the mRNA from the amino acid chain, and translation is
finished.
10. Tell the class that a ray (X-ray, UV ray, radiation, chemical exposure, etc.) just hit the
DNA on the banner, resulting in the changing of one base in the sequence. The G in the
ATG triplet was altered to a T (the triplet now is ATT). Cover the G on the card with a T
to indicate the change.
11. Ask the class to determine what effect the change might have on the protein that is made.
Direct the students to redo the above activity from forming the mRNA through building
the protein with the new DNA sequence.
Instructional Tip:
• Real-life examples apply here. Why does the dentist cover individuals with a lead apron?
Why does the X-ray technician stand behind a lead wall? Why should individuals use
sun screen? Why should individuals avoid tanning beds? All of these are protections
from radiation so that DNA is not mutated.
• The result should be a protein that is the same sequence of amino acids as the first but is
composed of four amino acids instead of six because the cosmic ray changed the UAC
codon (tyrosine) to a stop codon and therefore terminated the protein earlier than the
original sequence. Additionally, you may choose to first re-do this activity changing the
third base pair in the codon which does not change the amino acid showing students that
the codon can change without changing the protein.
12. Direct the students to record their answer in their notes at each step.
13. To close this lesson, ask students to reflect through a journal entry or a class discussion
on what happens when the sequence of amino acid sequence is changed. What happens
to the shape or size of a protein? How does this change affect function or characteristics
of the organism? Other changes may result in complications such as sickle cell anemia
and cancer. Tie this information into the engagement question. How does your DNA
relate to your physical characteristics such as eye color or the ability to roll your tongue?
Differentiated Instructional Support:
Instruction is differentiated according to learner needs to help all learners either meet the
intent of the specified indicator(s) or, if the indicator is already met, to advance beyond the
specified indicator(s).
•
•
Have students work independently, in pairs or heterogeneous groups to complete the
protein activity.
Challenge students to explore a genetic or medical condition of interest and share with
the class.
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DNA and Protein Synthesis – Grade 10
Extensions:
• Have students research other genetic diseases such as hemophilia, PKU or cystic fibrosis.
• Repeat this activity using an insertion or deletion in the sequence.
• Have students design an animation or dramatize the steps to protein synthesis.
Homework Options and Home Connections:
Invite students to examine the heritage of their pets or livestock, tracing physical
characteristics and traits.
Material and Resources:
The inclusion of a specific resource in any lesson formulated by the Ohio Department of
Education should not be interpreted as an endorsement of that particular resource, or any of
its contents, by the Ohio Department of Education. The Ohio Department of Education does
not endorse any particular resource. The Web addresses listed are for a given site’s main
page, therefore, it may be necessary to search within that site to find the specific information
required for a given lesson. Please note that information published on the Internet changes
over time, therefore the links provided may no longer contain the specific information related
to a given lesson. Teachers are advised to preview all sites before using them with students.
For the teacher:
Copies of Amino Acid Table which can be obtained in the textbook,
copies DNA sequences, index cards, banner.
For the students:
Copies of Amino Acid Table, copies of DNA sequences.
Library Integration Tips:
• Have students use the school library to use Infohio’s Access Science, NET Wellness and
school library books to get information about genetic mechanisms and genetic diseases.
Vocabulary:
• DNA
• RNA
• tRNA
• mRNA
• rRNA
• codon
• amino acid
• protein
• nucleotide
• transcription
• translation
Technology Connections:
• Have students use on-line amino acid tables and charts http://www.cbs.dtu.dk
• Have students look at a gene bank Web site that shows specific mutations.
http://www.ncbi.nlm.gov
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DNA and Protein Synthesis – Grade 10
Research Connections:
Marzano, R., Pickering, D., Pollock, J. (2001).Classroom Instruction that Works: Researchbased Strategies for Increasing Student Achievement, Alexandria, Va.: Association for
Supervision and Curriculum Development.
Nonlinguistic representations help students think about and recall knowledge. This
includes the following:
• Creating graphic representations (organizers);
• Making physical models;
• Generating mental pictures;
• Drawing pictures and pictographs;
• Engaging in kinesthetic activity.
Attachments:
Attachment A, Amino Acid/Codon Table
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DNA and Protein Synthesis – Grade 10
Attachment A
Amino Acid/Codon Table
20 Amino Acids with Their Corresponding DNA Codons
Amino Acid
DNA Codons
Isoleucine
ATT, ATC, ATA
Leucine
CTT, CTC, CTA, CTG, TTA, TTG
Valine
GTT, GTC, GTA, GTG
Phenylalanine
TTT, TTC
Methionine
ATG
Cysteine
TGT, TGC
Alanine
GCT, GCC, GCA, GCG
Glycine
GGT, GGC, GGA, GGG
Proline
CCT, CCC, CCA, CCG
Threonine
ACT, ACC, ACA, ACG
Serine
TCT, TCC, TCA, TCG, AGT, AGC
Tyrosine
TAT, TAC
Tryptophan
TGG
Glutamine
CAA, CAG
Asparagine
AAT, AAC
Histidine
CAT, CAC
Glutamic acid
GAA, GAG
Aspartic acid
GAT, GAC
Lysine
AAA, AAG
Arginine
CGT, CGC, CGA, CGG, AGA, AGG
Stop codons
TAA, TAG, TGA
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