Biology Commonwealth of Virginia

Objectives

• 
  summarize the main features of DNA replication;
  
• 
  write a complementary mRNA strand, given a DNA sequence;
  
• 
  summarize the process of transcription and translation.
  

Materials needed

• 
  Poster board
  
• 
  Legal-sized or larger paper
  
• 
  Markers, crayons, colored pencils
  
• 
  Yarn, string, pipe-cleaners
  
• 
  Tape and glue
  
• 
  Dried beans or peas
  
• 
  Toothpicks
  
• 
  Cotton balls
  
• 
  Rubber bands
  
• 
  Paper clips
  
• 
  Various types, colors, and weights of paper (colored index cards, adding machine tape, streamers, colored paper, punched holes from colored paper, etc.)
  
• 
  DNA or mRNA codon chart for referencing applicable amino acids
  
• 
  Copies of the attached group peer-evaluation form
  

Instructional activity

Content/Teacher Notes

Introduction

• 
  For the DNA molecule below, write out the resulting DNA molecules one would find at the end of DNA replication:
  

• 
  Given what you know about mRNA transcription and translation, use the codon chart to help you complete the blanks in the following table.
  

2. Have students put correct answers on the board so that the class can self-correct their answers.

3. Form groups of 2 to 4 students, choosing the groups in any way that best suits the population and level. Have students take their class materials with them to their groups.

4. Lead the class in the creation of a sample flow chart for “How to Make a Peanut Butter and Jelly Sandwich.” This is done to remind students of how to display the steps of a process sequentially. Once a few steps have been decided on by the class, displayed on the board, and copied down, ask the groups to spend 2 to 3 minutes illustrating these steps. This is done to model for students the type of flow chart that will be required in the activity that follows. Next, ask students to brainstorm ways that they could further illustrate these steps, using various three-dimensional materials.

5. Explain to students that they will be using the same methods to create and illustrate a flow chart to show the sequence of steps in DNA replication, mRNA transcription, and translation.

Procedure

2. Review with students the materials available (see “Materials needed” above) for them to use on their illustrated, three-dimensional flow charts, and encourage them to be creative in choosing materials. The list of materials might change depending on whether this is an in-class activity or something that the student groups complete outside of class.

3. Review with students the necessary components of their flow charts and the method that you will use to evaluate the final product. Explain that each group will present their product to at least one other group for formal peer review. Hand out copies of the attached peer-evaluation form. The following are some possible rubrics to be used for assessment:

• 
  Steps of replication, transcription, and translation are in the correct sequential order.
  
• 
  Flow chart is illustrated, and some portion of it is also three-dimensional.
  
• 
  Flow chart indicates the area(s) in the cell where each process occurs.
  
• 
  The nucleotide and amino acid sequences are correct regarding the given DNA sequence.
  
• 
  All members of group can explain the group flow chart.
  

5. Give students 10 to15 minutes to devise an initial plan or “rough draft” for their flow chart, which must be approved by the teacher.

6. Once the group plans have been approved, have the groups begin construction of their charts. Circulate to monitor the groups’ performance and offer guidance and assistance when necessary.

Observations and Conclusions

• 
  Did you use the DNA template strand to transcribe mRNA?
  
• 
  Is your mRNA molecule single stranded? Does it have uracil rather than thymine?
  
• 
  Do replication and transcription take place inside the nucleus? Does translation takes place in the cytoplasm?
  
• 
  Are the tRNA molecules individual and not in a strand?
  
• 
  Were you able to translate the mRNA codons into the correct amino acids?
  

Sample assessment

• 
  The product itself can be used as an informal assessment, but listed below are some questions to be posed to each group:
  

• 
  What is the purpose of DNA replication? Why is the transcription of mRNA from DNA necessary? Why is the last step of protein synthesis called “translation”?
  
• 
  What might be the result if the enzymes that control transcription did not function properly or not enough of these enzymes were produced?
  
• 
  How might the sequence of amino acids translated change if the mRNA was not transcribed from the template strand of DNA?
  

• 
  Have each group evaluate the final flow chart of and its presentation by at least one other group, using the attached peer-evaluation form.
  

Follow-up/extension

• 
  Following the construction and presentation of the flow charts, pose questions to the students about errors in the nucleotide sequences in their charts. This will lead the class naturally into a discussion about DNA and chromosomal mutations.
  
• 
  Have students draw examples of the following and explain the resulting amino acid or protein:
  

• 
  Point mutation
  
• 
  Frameshift mutation
  
• 
  Insertion
  
• 
  Deletion
  
• 
  Inversion
  
• 
  Translocation
  

Students in your group:

Students in the group you are evaluating:

1. Name a strength of the group’s flow chart and presentation:

2. Name a weakness of the group’s flow chart and presentation:

3. If there were any errors or pieces of the flow chart missing, list them here:

4. On a scale of 1 to 4 (1 being the lowest and 4 being the highest), how would you rate this group’s flow chart: _________
5. On a scale of 1 to 4 (1 being the lowest and 4 being the highest), how would you rate this group’s presentation: _________
6. Would you recommend that this group’s flow chart be used as a learning tool for other students? __________ Why, or why not?

Semantic Feature Analysis for DNA Replication and Protein Synthesis

Organizing Topic Genetics

Overview Students compare and contrast the processes of DNA replication, mRNA transcription, and translation. They use Semantic Feature Analysis to reinforce vocabulary.

Related Standards of Learning BIO.6f, g, h, i

Objectives

The students will

• 
  summarize the main features of DNA replication;
  
• 
  describe the structure and function of each type of RNA;
  
• 
  write a complementary mRNA strand (A-U, T-A, C-G, and G-C);
  
• 
  summarize the processes of transcription and translation.
  

Materials needed

• 
  Copies of the attached student activity sheet
  

Instructional activity

Content/Teacher Notes

Semantic Feature Analysis (SFA), a strategy used primarily for reinforcing vocabulary, can be used as either a pre-reading or a post-reading activity. SFA involves establishing links between prior knowledge and words that are conceptually linked, analyzing words for similarities and differences, and categorizing words based on how well they fit into pre-established conceptual categories.

In an SFA activity, students are provided with a chart or grid with on which to analyze the similarities and differences among related concepts and then decide whether each concept is a member of one of the categories on the grid. The concepts are typically “new vocabulary,” and this strategy is most helpful with concepts that share major themes or roles in the content. In addition to students placing a “Yes” or “No” mark under each category, they may use a question mark if they are uncertain about a particular concept.

This type of lesson is typically used with students needing some additional reinforcement of the biology terminology that appears in most textbooks. Students should do this lesson after they have already learned about the processes of DNA replication and of protein synthesis. This is an excellent post-reading lesson to use with ESOL Biology students or with other student populations needing extra vocabulary reinforcement.

Introduction

1. As an introduction to Semantic Feature Analyses, have students write lists of characteristics that are particular to the following three groups or categories: cats, dogs, and birds. Once they have written a few characteristics for each group, lead a class discussion about how they chose those characteristics to go into each category.

2. Explain that the students will be give a list of statements and asked to chose which one best describes one of the processes associated with nucleic acids, using SFA to decide which statement fits with which process.

Procedure

1. Introduce the general structure of an SFA. You may with to use a model if this is the first time the students will be using this strategy. Make sure that students understand whether the SFA is being utilized for pre- or a post-reading purposes.

3. As a pre-reading strategy, let students spend some time working individually on the SFA chart or grid. Depending on the rest of the agenda, allow students to share their responses with another student or a small group. Discuss different student responses as a class. Assign related reading, and ask the students to make changes to their initial responses if the reading changes their minds.

4. As a post-reading strategy, assign related reading, and ask students to complete the SFA chart or grid individually. Have students share their responses with another student or small group, and have them make changes or corrections based on their reading. Use class discussion to ensure that all students agree on their choices.

Observations and Conclusions

1. Have students complete the student activity sheet. Then, hold a class discussion of the responses. The answer key is shown below:

Description of Process	Replication	Transcription	Translation
Involves only DNA	
Involves both DNA and RNA		
Involves only RNA			
Process of creating amino acid sequences by reading the sequence of nucleotides off of an mRNA strand			
Process of making a complete and exact copy of a molecule of DNA	
Process of making a single-stranded mRNA molecule from a molecule of DNA		
Involves the unwinding and unzipping of a DNA molecule to begin		
Involves both mRNA and tRNA			
Involves only DNA and mRNA		
Takes place inside the nucleus		
Takes place at the ribosome in the cytoplasm			
The product, mRNA, of this process leaves the nucleus after its production.		

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