Summer Research Program for Science Teachers
ROY AREZZO - I.S. 318
1997
SEVENTH GRADE BIOLOGY
Trichinella Forensics
PRE-LESSON TOPICS/EXPERIMENTS:
A. MEASUREMENT:
1. Metric System; length, mass, volume, density
* -incorporate micro pipetting into laboratory exercises involving measurement
* -demonstrate how substances of different sizes migrate through various mediums
B. GENETICS:
1. Inheritance [5-8 Content Standard C- Reproduction and heredity]
2. DNA/RNA structure and function
3. DNA replication/transcription
4. Protein synthesis [5-8 Content Standard C- Structure and function in living systems]
C. MOLECULAR GENETICS TECHNOLOGY:
1. Gene mapping/human genome project
2. Cloning/restriction enzymes/vectors
* 3. PCR/electrophoresis/southern blot analysis, etc
D. PARASITOLOGY/EPIDEMIOLOGY:
1. Parasite/host relationships and other symbiotic interactions [5-8 Content Standard C- Diversity and adaptations of organisms]
2. macroscopic and microscopic laboratory study of parasitic organisms/pathology
* 3. Life cycles of parasites/school presentation by Dr. Despommier [Teaching Standard D- Identify/use resources outside the school]
* 4. Use of genetics/ medical technology in pathology [5-8 Content Standard F- Science/technology in society]
* Starred items are subjects that will be used to update content.
Trichinella Forensics
INTRODUCTION:
Today, we are inundated by the media with topics glorifying the new genetics age. Although real science is often at the backbone of these stories, too often such topics are presented in a tabloid fashion. From criminal forensics to paternity suits, cloning and Jurassic Park, molecular genetics technology is treated as science fiction and regarded as the work of an elite breed of super-scientists.
Through an introduction to molecular genetics, engage the students in the theories and practices which are at the core of these current events. Using standard procedures of the modern genetics laboratory to compliment the current biology curriculum, students will manipulate DNA and gain appreciation for how it can be used as a tool to address some of the practical problems of society.
LESSON PLAN
TITLE: Trichinella Forensics
SUBJECT: Seventh Grade Biology
UNIT: Genetics
AIM:
Who did it ? (The uses of DNA fingerprinting)
MOTIVATION:
Students will engage it the procedures used in "real science" to manipulate DNA. Students will be brought on a field trip to an actual research laboratory at Columbia University to conduct hands-on science activities. [Teaching Standard D- Identify/use resources outside the school]
OBJECTIVES:
Students will be able to:
-work cooperatively in research groups
-work safely in a laboratory setting
-explain concepts relevant to lesson; i.e. inheritance, DNA replication, electrophoresis, etc.
-use micro pipette to retrieve/dispense small volumes of solutions
-follow the protocol necessary to prepare ribosomal DNA for PCR
-set up a gel plate for electrophoresis study
-prep the DNA solutions for use in gel electrophoresis
-load the wells of agarose gel with the appropriate concentration/volume of materials
[Teaching Standard D- Make accessible science tools]
[5-8 Content Standard E- Understandings about science and technology]
-observe and interpret the results of gel electrophoresis
-graph electrophoresis data with respect to molecular weights (base pairs)/migration (mm)
-identify bands on a gel and use DNA information to identify an organism
TEACHING SEQUENCE:
Students will be divided into small research groups of two or three. Dr. Despommier will address the group with a short presentation/slide show on the life cycle of Trichinella spiralis.
Laboratory Procedures:
Polymerase Chain Reaction is a modern technique that allows one to amplify the amount of a particular sequence of DNA through enzyme activity. The process is a chain reaction in that for each round of PCR, each strand of DNA is replicated. If one strand of DNA is replicated into two new strands those two strands would replicate into four the next round and so on. Thus the amplification process is exponential resulting in a large amount of DNA in a relatively short period of time. Heat is used to separate DNA strands so that each strand can be replicated When the sample is cooled the polymerase the enzymes catalyzes the combination of nucleotides for the synthesis of new strands containing specific oligos.
Ribosomal DNA from human, mouse, rat, trichinella and another nematode specie (each sample will be treated as unknown) will be used in this activity. Ribosomal DNA is optimal for this activity since it requires less rounds of PCR to amplify into a large amount.
Electrophoresis is a technique which involves the migration of charged molecules through an electric field. [5-8 Content Standard B- Motions and forces] This technique can be used to separate and identify proteins and nucleic acids. The gels used in electrophoresis are composed of agarose is a matrix composed of purified agar. Varying the concentration of agarose (we will use 1% agarose) will vary the pore size for molecules to travel through. The molecule density determines the distance it will travel (other variables include intensity of the electrical field and charge and shape of the molecule). Using known markers one can determine the size of a fragment based on the distance it has migrated. The use of this technology in DNA fingerprinting is achieved by identifying unique bands on a gel. Since all sexually reproducing organisms have unique genes, the sequence of their DNA strand varies from organism to organism. These different sequences also vary in size, thus when a gel is run the individual’s DNA can be identified by unique bands. [Content Standard Unifying Concepts- Evidence, models, and explanation]
Students will set up complete gel electrophoresis plates, and load the wells with the amplified mammal and nematode DNA after PCR is complete. Each unknown sample will be labeled using letters or numbers. They will add loading buffer to the samples and prepare one lane of lambda DNA (cut with the enzyme HindIII) to serve as a molecular weight marker. After running the gel for 45 - 60 minutes the gels will be viewed under UV light to detect distinct bands. Successful migrations will be photographed for data analysis. Using the image of the bands relative to the molecular weight marker, students will graph the data to determine the size of the bands. [5-8 Content Standard A- Using mathematics]Using the size of the bands relative to known band lengths students will determine the origin of each sample. It will also be useful to identify similarities in the genome of different organisms for evolution discussions back in the classroom.
EVALUATION:
Students will write up laboratory reports based on the activities listed above.
POST- LESSON/EVALUATION:
A. How to write a laboratory report.
B. Students design an experiment that would enable them to use the technology available to identify individuals by their specific DNA pattern.
C. Ethical issues surrounding the use/monitoring of molecular genetics technology.
[Teaching Standard B- Orchestrate scientific discourse]