|A collaboration of the New York City Department of Education and the Dolan DNA Learning Center, Cold Spring Harbor Laboratory
The project team has worked to develop a limited set of “icon” laboratories, which embody process skills and key concepts of genetics and biotechnology. The juxtaposition of two major genetics/biotechnology units in 8th and 9th grades provides an opportunity to move students from descriptive to quantitative analysis of genetic processes – in keeping with the DOE's “spiraling curriculum” in which topics are revisited in greater depth in successive years.
DNA Structure and Isolation
Through interviews and animations, DNA Interactive (www.dnai.org) introduces students to the “players” and “the pieces of the puzzle” they contributed to solving the structure of DNA, including Nobel Laureate James D. Watson, formerly of Cold Spring Harbor Laboratory. This rich historical story can be complemented with easy-to-build DNA models and DNA extractions from bacteria, food, or human cheek cells.
Variability and Inheritance
Students reflect upon humankind’s earliest attempts at genetic engineering – selective breeding of agricultural plants and animals. By studying a landmark experiment conducted by George Shull at CSHL, students observe hybrid vigor in corn, which is the basic method used to make all hybrid corn in the U.S. and abroad. The same basic principles of inheritance apply to humans.
Mutations and Variability:
At a the beginning of the 20th century at Columbia University, Thomas Hunt Morgan used mutant fruit flies to understand the physical basis of heredity, showing that genes indeed occupy specific locations on chromosomes. Drosophila and the round worm C. elegans can show students how model organisms help scientists understand mutations, variability, and natural selection. Identifying distinctive looking flies among a mixture of dead Drosophila, or behavioral mutants among living C. elegans, hones observation skills and cements the relationship between mutations and traits.
DNA Transformation and Protein Isolation
Hands-on laboratories offer a stimulating means to integrate the concepts “gene” and “genetic engineering” that are present in the 8th grade unit of the NYC Scope and Sequence. Student experiments recreate work done in Martin Chalfie’s laboratory at Columbia, where green fluorescent protein (GFP) was first cloned into E. coli. The GFP protein is then isolated by a simple “batch” method, which illustrates how many biotech products are produced.
DNA Analysis and Forensics
The applied use of restriction enzymes to precisely cut DNA arose from basic research on the interaction of bacteria and their parasitic viruses, the phages. CSHL Nobelist Richard Roberts popularized the use of restriction enzymes in research. Using restriction enzymes and gel electrophoresis, students can digest and analyze DNA in the same way. The DNA Interactive Internet site traces the development of DNA fingerprinting, and its use in forensic DNA analysis.
PCR and Human DNA Variations, Part I & II
Experiments on students’ DNA polymorphisms – including Alu insertions and mitochondrial point mutations – extend the description of genotype-phenotype to the molecular level. Deriving population measures from class results and analyzing common ancestry with bioinformatics provides links between genetics and evolution – which follow one another in the Living Environment syllabus. An online excursion to the Eugenics Archive can show how New York Institutions led a misguided effort to use genetic selection to artificially guide human evolution.
Genetically Modified Foods
During the “green revolution” of the 1950s through 1970s, high-yielding strains of wheat, corn, and rice – coupled with extensive use of chemical fertilizers, irrigation, mechanized harvesters, pesticides, and herbicides – greatly increased world food supply. Results were especially dramatic in underdeveloped countries. Now, genetic engineering is fueling a “second green revolution.” Genes that encode herbicide resistance, insect resistance, drought tolerance, frost tolerance, and other traits have been added to many plants of commercial importance. Most Americans would probably be surprised to learn that more than 60% of fresh vegetables and processed foods sold in supermarkets today are genetically modified by gene transfer.
This laboratory uses a rapid method to isolate DNA from plant tissue and food products containing soy or corn. Then polymerase chain reaction (PCR) is used to assay for evidence of the 35S promoter that drives expression of the glyphosate resistance gene (resistance to Round Up® herbicide) and many other plant transgenes. Since soy and corn are ingredients in many processed foods, it is not difficult to detect the 35S promoter in a variety of food products.
Howard Hughes Medical Institute, Bodman Foundation, Dana Foundation,
Jerome L. Greene Foundation, Goldman Sachs Foundation, and William Townsend Porter Foundation