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Biotechnology and The Chocolate Milk Cow

By Craig Kuchel


New discoveries resulting from the use of recombinant DNA technology are already beginning to have an impact on the lives of high school students. A basic understanding of recent developments in molecular biology is becoming increasingly necessary if we intend to have a society that is scientifically literate and capable of making informed decisions on important biological and ethical issues which arise. Many teachers have already incorporated aspects of the "new genetics" into their curricula. However, all too often units on biotechnology focus on isolated concepts and are too abstract to enable students to really understand how the many new techniques and tools blend together to form an exciting new scientific discipline. This activity represents an attempt to promote a better understanding of recombinant DNA science through collaborative learning and application of new knowledge to the solution of a specific problem.



  • simulation
  • authentic assessment

  • Advanced Biology
  • "Do you think somebody could really make a cow that produces chocolate milk?"

    "But wouldn't we also have to splice in a gene from a sugar cane plant to make the milk sweet?"

    "This is a lot like that article from 'Science' we just read on 'Pharming', creating genetically-engineered animals to produce human pharmaceuticals in their milk. Nobel Prize here we come!"

    Those are typical of comments heard in the biology II class on the day that students receive their assignment to design a workable plan for creating a cow genetically-engineered to produce chocolate-flavored milk. It seems that political instability and the vagaries of climate have combined to produce escalating prices which will soon make chocolate milk a luxury to be enjoyed by only the very wealthy.

    Many high school biology teachers now include a unit on biotechnology in their curriculum. Typically those units consist of an introduction to terminology germane to the subject, hands-on experiences using models and simulations, labs which may involve manipulating DNA and using gel electrophoresis to sort DNA fragments by size, and a consideration of the potential of genetic engineering and some of the possible ethical issues which accompany this new technology. Students may be introduced to a variety of the tools used by molecular biologists, and they often use some of those tools, notably restriction enzymes, in lab activities they perform. However, most students fail to develop an understanding of how those tools are used together to accomplish some of the goals of genetic engineering. There is no culminating activity which requires students to synthesize their newly-acquired knowledge and apply that knowledge in solving a problem related to DNA technology. This activity provides an opportunity for students to develop a deeper understanding of the many tools and techniques used in recombinant DNA work, to collaborate and think creatively and logically, and to gain an appreciation for how complex genetic engineering really is.

    The assignment is to create a transgenic cow capable of producing chocolate-flavored milk. With one exception, the assumption that chocolate flavor is entirely due to a single polypeptide produced in the cocoa plant, the project is very realistic. Students collaborate in small groups or work alone to develop strategies for isolating and cloning the gene, attaching regulatory sequences, developing a method for delivering the gene to the new host, and more. Ultimately, each student designs a protocol to be submitted to the Recombinant DNA Advisory Committee for review.

    There is no single way to solve the problem, but students are aware that their individual plans, which will require many steps, will be peer-reviewed, and must be scientifically valid throughout. Evaluation of the proposals is based on how thorough the approach is, how accurately proposed techniques are described, and how well it would actually work if put into practice.

    The time necessary for this activity will vary depending on how much detail and depth of understanding the teacher wishes. My classes usually spend a minimum of two weeks researching and strategizing in class; final papers are prepared outside class. A wide variety of resources is made available to the students as they work to develop a protocol to accomplish their task. Some of the most valuable resources are textbooks and lab manuals which detail recombinant DNA techniques. Catalogs available from the many suppliers of chemicals, equipment, and kits used in actual biotechnology research applications provide a wealth of valuable information on various protocols.

    Additionally, several publications routinely received by molecular biologists contain information on techniques and equipment which can be incorporated into the protocol. Students also access CD-ROM databases containing references to recent articles in the popular literature and go online on internet and AOL to access information in libraries and professional journals, and pose questions to researchers in the field of transgenic animals.

    This assignment follows a set of lessons which begins with a review of basic information about the structure of DNA. Then the students, by using computer software, reading numerous articles, and building models, develop a thorough understanding of the tools of the genetic engineer. Finally, they perform a series of lab activities in which they learn and use many techniques used in advanced biotechnology research facilities; they isolate, purify and map bacterial plasmids to determine the identity of the plasmid and then use that plasmid in a bacterial transformation activity.

    When assignments are handed in, the class is divided into several groups and each review team evaluates several of the proposed protocols. The review teams exchange those proposals receiving the most favorable reviews. Finally, a number of the proposals are selected for presentation to the class. Tension runs high as the students explain the details of their proposals in presentations to their peers. They know that only one of them will be able to receive this year's prestigious Chocolate Cow Award (an award which rates right up there with the Nobel Prize). Finally, the session ends and the Chocolate Cow Award is in the hands of the proud new recipient; students realize that they have experienced something very close to the excitement actually generated in those high-tech laboratories where genes are being spliced and organisms redesigned in an effort to improve the human condition around the globe. In an activity which began as a whimsical effort to save children of the world from the rising price of chocolate milk, students have experienced science the way scientists do. They have collaborated, been creative, researched ideas, and applied knowledge in an attempt to solve a problem. The rewards, they have found, are plentiful! They have developed an appreciation and understanding of a complex new technology which is already impacting their lives.

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