This unit is intended for a senior honors or Advanced Placement Biology class and will require about two to four weeks to complete depending on the students’ aptitude and prior knowledge. The New Haven Public Schools Science Curriculum demonstrates a commitment to the discussion of current science events among its teachers and students. The questioning of modern biological techniques and the discussion of its social and moral implications is a vital part of a science curriculum; this includes any legal issues that may arise. The bullets to be covered in the unit stem from the Connecticut Common Core of Teaching and Learning and were adapted by The New Haven Public School science curriculum committee; they include:
1. Prepare and defend a position on the ethics of genetic engineering
2. Prepare persuasive writing on gene splicing and cloning
3. Prepare and deliver oral presentations on possible benefits and problems of recombinant DNA technology
The objectives of this unit are as follows:
- Students will be able define cloning, including the various types
- Students will be able to construct a timeline of the history of cloning (1880 to present)
- Students will be able to simulate the processes of bacterial cloning (Recombinant DNA) and reproductive cloning.
- Students will be able to research and evaluate landmark court decisions and legal precedents to develop an argument as to whether people have the right to clone oneself.
While the first three objectives will provide the necessary scientific knowledge for the student to prepare a presentation it is not the main focus of the unit, the legal issues surrounding cloning and whether or not we have the right to clone is the ultimate issue. The objectives lend themselves well to a variety of classroom activities that include Bloom’s Taxonomy and Multiple Intelligence theory. Bloom’s Taxonomy works under the principle that higher level thinking can only be achieved if the student first comprehends the information. After comprehension is achieved, then the student will be able to process and synthesize the material. The final stage of Bloom’s Taxonomy is evaluation.
In this unit the student must first understand the basic biological process that produce clones, they will have the opportunity to simulate cloning in the lab and witness first hand the problems associated with the process. They will then read articles that deal with ethical and legal issues surrounding cloning and related subjects. With this information the student will have a balanced view of the subject, that is they will understand the negative and positive aspects of cloning. It is only at this point that the students can critically look at the issue and make their own evaluations and informed opinions. The point of any good science curriculum is to ensure that the student is armed with the tools to make them productive and informed citizens, ready to contribute to society.
This unit is scientific inquiry based, which also allows for the development and assessment of the student’s critical thinking skills. Inquiry based assessment allows the students to learn while doing. The students themselves develop the questions that they want answered thereby making the subject more relevant to their needs and experience. The laboratory activity is a hands-on activity that is in keeping with sound multiple intelligence theory. The students will be called on to use their emotional, intrapersonal and interpersonal intelligences as well.
So what exactly is cloning?
In biology, the noun “clone” refers to a cell, an organism that is genetically identical to another cell or organism from which it is derived. The verb “(to) clone” refers to the process of creating cloned cells or organisms. There are three main types of cloning, Recombinant DNA technology or DNA Cloning, Reproductive Cloning and Therapeutic Cloning. When there are news reports on cloning they are usually speaking of Reproductive Cloning, which is “a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal” (). It is this type of cloning that is the most difficult to execute successfully, and the one that sparks the most heated debate.
To put it very simply, a clone is a copy of another organism that has the exact same DNA as the original.
1. Recombinant DNA Technology (DNA cloning) is the “transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid.” (www.ornl.org)
2. Therapeutic cloning which is also called embryo cloning, this is the “production of human embryos for use in research” () this is commonly referred to as ‘stem cell’ production. The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease.
3. Reproductive cloning which is a “technology used to generate an entire animal that has the same nuclear DNA as another currently or pre existing animal” () for example Dolly the sheep.
To nature, the process of cloning is nothing new it has been doing it for millions of years. Anyone that has done some gardening has probably witnessed cloning in action. When plants send out runners making new plants or we take a cutting of one plant to produce another, each new plant is a clone of the original. Certain animals have the ability to clone themselves; for instance the tiny water animal hydra can clone an entirely identical hydra form the original if a small part is cut off. In a process certain animals like salamanders and lizards, under the right conditions can undergo
to make an exact clone of themselves. And of course the most obvious cloning in nature is the existence of identical twins. When the sperm fertilizes the egg an embryo is formed. Usually the embryo will divide and create one fetus. But sometimes the fertilized egg splits into two forming identical embryos that develop into two people with exactly the same DNA.
Nature has been cloning all along, and now it seems that humans are catching up. But while most people only became aware of our ability to clone animals with the birth of dolly the sheep in 1997 (the first cloned mammal) cloning in other animals had been relatively successful many almost a century prior. 1902 the German Embryologist Hans Spemann used a strand of human hair to tie around the embryo of a salamander and split the cell in two, mimicking the natural process of making identical twins. The result was two salamanders with identical DNA. Spemann had a vision of a “fantastical experiment”, he suggested that an organism could be cloned if nuclear material could be transferred into an egg. The technology of his time limited him to a dream, but it is his idea that was the basis of cloning today.
In the in 1960’s John Gurdon did exactly what Spemann had proposed. He took an egg from a frog (Frog A) and blasted it with radiation, which destroyed the nucleus. Then he took a fully differentiated cell from the skin of another frog (Frog B) and removed the nucleus. The nucleus from frog B was then implanted into the enucleated egg from frog A. The end result was a tadpole that was a clone of frog B.
It was this fundamental technology that led to Dolly. Dolly was cloned at the Edinburgh-based Roslin Institute by a team lead by Ian Wilmut. He and his colleagues built on the technology of Gurdon’s experiments. Wilmut et al. had to reprogram the DNA of the donor sheep so that the cell would not develop into the part that it was taken from. An egg was taken from a Scottish Blackface sheep shortly after the sheep ovulated, the nucleus was removed with a pipette. Then the adult cell was taken from the mammary gland of a Finn Dorset sheep that was completely white. This cell was “starved” (denied nutrients) and not allowed to grow or divide. Then both cells were placed next to each other and electricity was used to jolt the cells into merging. The cell divided and developed into a normal embryo and was implanted into a surrogate mother that was also a Blackface sheep. When Dolly was born she was completely white, evidence that she was indeed a clone of the Finn Dorset sheep. This is shown in a fabulous diagram at www.howstuffworks.com
Cloning Timeline from A Brief History of Cloning (1880 to present)
1880 August Weissmann states that genetic information of a cell diminishes with each cell
1902 Hans Spemann divides a salamander embryo in two and shows early embryo cells
retain all the genetic information necessary to create an organism
1928 Hans Spemann performs the first nuclear transfer experiment
1938 Hans Spemann proposes a “fantastical experiment” to transfer one cell’s nucleus into an egg without a nucleus, the basic method that would eventually be used in cloning
1952 Briggs and King clone tadpoles
1953 Watson and Crick discover the structure of DNA
1962 John Gurdon clones frogs from differentiated cells
1963 J.B.S. Haldene coins the terms ‘clone’
1978 The release of David Rorvik’s book,
In His Image: The Cloning of Man
, sparks a worldwide debate on cloning ethics.
1980U.S. Supreme Court rules live, human made organisms are patentable material
1990 Human Genome Projects begins
1996 Dolly, the first mammal cloned from adults cells, is born (not announced until 1997)
2000 Britain becomes the first country to grant a patent for cloned early-stage human embryos. Genron Corporation, which received the patent, says it has no intention of creating cloned humans
2000 Human Genome Project ends