Summer Research Program for Science Teachers

How Mutations Lead to Changes in Cell Structure and Function

Mary Ann Spicijaric - 1995

St. Francis Preparatory H.S., Queens, NY

Objectives:

To become familiar with the mechanism and importance of DNA repair.

To understand the difference between DNA damage and mutations.

To see how mutations lead to changes in cell structure and function. [Content Standard C- The cell] [Content Standard C- Molecular basis of heredity]

Materials:

ball and stick model of DNA

ball and stick model of RNA

table to decode mRNA codons

wild type yeast cells and rad 12 mutant cells [Teaching Standard D- Make science materials accessible]

microscopes and slides

pen and paper

masking tape

Procedure:

1. Students construct an oligonucleotide of a given length and sequence.

2. Through the use of models, students carry out transcription and translation.

3. Using the mRNA codon table, students decode the message and identify the protein sequence.

4. Masking tape will be placed on the model to indicate an area of UV damage.

5. Students are asked to design a step by step mechanism of how they think cells repair the damaged DNA. [Content Standard Unifying Concepts- Evidence, models, and explanation]

6. One member of each group will explain the group mechanism to the class. [Teaching Standard B- Orchestrate scientific discourse]

7. The teacher allows for discussion of the different mechanisms and then presents nucleotide excision repair and base excision repair.

8. Teacher gives the class the same general oligo sequence as before but with a few nitrogenous base changes.

9. The students go through the same steps of transcription and translation to decode the now different amino acid sequence.

10. Teacher will elicit from the class the difference between DNA damage and DNA mutations.

11. Students will then prepare slides of wild type yeast cells and rad 12 yeast cells. The rad 12 cells will appear long and distorted by comparison. The students will be asked to postulate why these cells may appear this way. [Teaching Standard B- Orchestrate scientific discourse]

12. After discussion, the teacher can explain that rad 12 cells have a mutated gene that keeps the cell in the G2 part of the cell cycle.

13. Terms to review: DNA damage, mutations, DNA repair, cell cycle, G2 arrest, nucleotide excision, base excision, oligonucleotide

 Please note that this plan should span 3-4 days

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