Summer Research Program for Science Teachers
Monika Biro
1999
Professional Children's School
Learning the Structure and
Function of DNA
GRADE LEVEL: 9th & 10th grades
OBJECTIVE: Students will learn about the structure and function of DNA and will do a gel-electrophoresis lab [9-12 Content Standard E- Understandings about science and technology], where they will be able to relate the size of polynucleotides and their ability to move in electric current through an agarose gel [9-12 Content Standard B- Structure and properties of matter]. Students also will participate in an Internet activity, where they will be able to test their knowledge and will participate in a discussion about the difficulties, advantages and ethical issues of the Human Genome Project.
COMPONENTS OF THE LESSON PLAN:
· Cooperative learning activity
· Laboratory exercise
· Internet activity
COOPERATIVE LEARNING ACTIVITY
OVERVIEW:
DNA is a macromolecule that forms a double helix structure in the cells (mostly in the nuclei and mitochondria) of living organisms. This double helix is made up of a combination of millions of four different types of nucleotides as monomers. However, these monomers are also very complex molecules that are created from the covalent bonds of a phosphate group, a five carbon sugar called deoxyribose and one of four nitrous bases: adenine, guanine, cytosine and thymine. Two parallel DNA chains are connected by the nitrous bases. A nucleotide with adenine is always bonded to a thymine on the opposite chain. A nucleotide with guanine is always bonded to cytosine on the opposite chain. [9-12 Content Standard C- The cell]
TIME FRAME:
Two 45-minute periods.
MATERIALS:
· Pens and pencils
· Scissors
· 6 different types of colored paper
· VCR
· Film on DNA
· Notebook
PROCEDURES:
Have students work in groups of three to:
1. watch the film and answer the given review questions with their group
2. cut out the different components of the nucleotide from the colored paper and build up a polynucleotide section by using the given order of nitrous bases on one side of the DNA double helix
3. put the completed polynucleotide chain together with other groups in the given order
ACTIVITY SHEET:
Answer the following questions after watching the video film.
1. What is the basic shape of DNA?______________________________
2. What is the function of DNA in the cells of living organisms?
_______________________________________________
[9-12 Content Standard C- The molecular basis of heredity]
3. What is the monomer of a DNA molecule? ______________________
4. What are the four bases that determine the type of nucleotides?
_______________________________________________________
5. How do bases bond two parallel DNA chains?
________________________________________________________________________________________________________________
6. What are the other combining molecules of nucleotides?
________________________________________________________
Make a model of a portion of a DNA molecule by using the colored papers provided. In your model please use the sequence of bases given in one chain of the DNA and build the nucleotides with the complementary bases in the parallel chain.
LABORATORY EXERCISE
TIME FRAME:
Two 45-minute periods.
OBJECTIVES:
· Preparation of agarose gel
· Learning the principles of gel electrophoresis
· Observing results and identifying unknowns by measuring their migration distances and comparing them to known substances [9-12 Content Standard A- Formulate explanations using evidence]
· Writing a lab report
MATERIALS:
· Gel electrophoresis kit
· Markers
· Unknown DNA fragments
· Graphic paper
· Pencil
· Ruler
· Notebook
· Pen [Teaching Standard D- Make accessible science tools]
INTERNET
ACTIVITY
TIME FRAME:
One 45-minute period.
OBJECTIVES:
· Students will test their knowledge of the structure and function of DNA
· Students will learn about the Human Genome Project
· Discussion of the importance, difficulties, and ethical issues of the Human Genome Project.
[9-12 Content Standard F- Science and technology in local, national, and global challenges]
PROCEDURES:
1. Each student will download the nucleic acid problem set on http://www.biology.arizona.edu to look at the DNA structure and answer some of the multiple choice questions - about 10 minutes.
2. Students will read about the Human Genome Project on http://www.nhgri.nih.gov/HGP --about 10 minutes.
3. The class will discuss the importance, advantages, difficulties and ethical issues of the Human Genome Project - the remainder of the class time. [Teaching Standard B- Orchestrate scientific discourse]