This lesson is designed to present transition mutations to high school seniors. After this lesson, students will be able to:
- Describe the double helix structure.
- Discuss the importance of DNA as the genetic material.
- Explain how DNA replicates.
- Explain how Transcription and Translation occur.
- Describe how DNA directs the synthesis of proteins
- Describe what Point Mutation is.
- Explain how Transition Mutation occurs.
Students will also know the following vocabulary:
DNA, Double Helix, tRNA, mRNA, Complementary Base Pair, Polypeptide, Transcription, Translation, Purine, Pyrimidine, Transition Mutation, Point Mutation ,Amino acids, Adenine, Thymine, Guanine, Cytosine, Uracil, Protein, Codons.
The following powerpoint presentation will be used to instruct the class: Transitional Mutation Power Point
The following in class activity is designed to offer a visual reinforcement of the powerpoint slide show.
DNA models, Charts of DNA structure, Charts of protein synthesis, Buttons with A, T, C, G, and U written on them, Sheets of colored papers (1cm^2) representing all the amino acids, glue tape ( to hold down colored paper ), Sheets of white paper, Triplet code chart.
Color Representation: Serine (Ser)= Red, Glutamine ( Glu) = Blue, Valine (Val)= Violet, Lysine (Lys)=Cyan, Phenylalamine (Phe)=Brown, Threonine (Thr)= Black, Tyrosine(Tyr)=Yellow, Isoleucine (Ile)=Pink, Stop Codons =Orange.
1. Using Buttons (with A, T, C, & G, written on them) instructor demonstrates to students how a transition mutation occurs.
Sequence of part of a normal gen Sequence of part of mutated gene
2. Students will be given the following questions to assess understanding:
- Is the transition mutation AT-to-GC, GC-to-AT, TA-to-CG, or CG-to-TA?
- Where within the triplet codons does the transition mutation occur? Explain.
- Why is it an example of a point mutation?
3. In groups of four (and using several A, T, C, & G bases), have students create their version of the four types of transition mutation. A data table containing names of group members and their types of transition mutations are written on the board.
- Sequence of part of a normal gene Sequence of mutated gene
- Group A: 5’ ---------- 3’ 5’ ----------3’
- 3’---------- 5’ 3’ ---------5’
- Group B: 5’ ---------- 3’ 5’ ---------- 3’
- 3’ ---------- 5’ 3’ ---------- 5’
4. Using the buttons, students create a double stranded DNA model with a sequence of about 15 bases. For example:
- 5’ …TCTCAAAAATTTACG… 3’
- 3’ …AGAGTTTTTAAATGC…5’
Next, students create the same DNA model as it begins the process of replication.
5. With the double stranded DNA molecule created in (Dev. 10), students are asked to create a new version of a transition mutation.
- Group A:This group will show how transition mutation occurs from AT-to-GC.
- Group B: This group will show how transition mutation occurs from GC-to- AT.
- Group C: This group will show how transition mutation occurs from TA-to-CG.
- Group D: This group will show how transition mutation occurs from CG-to-TA.
Each group completes a five-part word wheel with the title: “functions of DNA” in the middle circle, and one function for DNA in each of the outer circles:
- Stores information
- Replicates and passes on information
- Ability to remain relatively stable
- Ability to mutate
Each group will answer the following questions:
1. Question: In any sample of DNA, the amount of A is equal to the amount of T and the amount of G equals the amount of C. Why does this happen?
- Answer: That A pairs with T, and G pairs with C
2. Question: Given the following information: 5'-GGTCTCAAAAAC-3', determine the sequence of the opposite strand?
- Answer: Two strands are complimentary because of DNA’s base-pairing rules.
3. Question: Given a nucleotide sequence 5 bases long, how many combinations of sequences could you create?
- Answer: Combinations: 4x4x4x4x4=4^5=1,024 combinations
4. Question: During replication, what information must be passed on?
- Answer: When the chromosomes in cells replicate it is really the DNA making a copy of itself. Thus, chromosomes equal DNA and protein.