b) The experiment was widely criticized by scientists and the general public. Scientists argued that the sheep from which Dolly was cloned was pregnant. It is well known that fetal cells often circulate through the mother`s bloodstream and body , that it was quite possible that one of the fetal cells of that lamb rather than the adult mammary cells of the purported adult donor, was in fact cloned instead. This isn’t all that remarkable, as fetal cells are cloned all the time and even nature does it when identical twins are born.
Scientists’ criticized the use of an electric pulse, they argued that DNA errors may have occurred and also unknown long-term complications such as genetic defects being amplified as successive cloning may cause mutations in a somatic cell to accumulate. The scientists who created Dolly could not rule out the possibility of a mutation or other biological damage ().
Animal protection activists like the S.P.C.A argued that the production of Dolly was in violation of the uniqueness of the natural process of reproduction that occurs in all living things. They also argued that due to the process involved in extraction of the somatic cell and oocyte from respective animals, what kind of suffering is caused to the animals during the process of extracting the cells (Prakash S. L; 2005). They also criticized the extent to which scientists were willing to improve animals by increasing the natural capacities? In other words should we use them solely for our own ends?
Human activists against cloning criticized the cloning of Dolly criticizing the repugnance of a style of reproduction with such profound potential for vanity, arguing that if human cloning was to be done the freedom of children and nature of the family are in danger. They criticized the fact that a clone like Dolly lacked traits necessary for true independence from "parent" progenitors. They criticized that the cloning of Dolly violated the animal`s right to an open future ().
Different religious sects opposed the cloning of Dolly arguing that the bible tells us that originally man and woman were one being, but that God separated them after creation. When a man and woman marry, they come together to form the original whole. Cloning unduly interferes with the deeply held belief that God created the world such that a man and woman would unite to “be fruitful and multiply,” (Genesis 1:28) creating new life together. They argued that cloning interferes with the basic process of procreation itself. The normal sequence of egg and sperm uniting and forming a new life is abolished and the egg becomes a vehicle for the “parasitic” parental DNA. Basically, sexual reproduction is replaced by a new version of parthenogenesis; they by replacing the rightful place of God in the Procreative process (Daniel Eisenberg; 1997).The general public argued that to what extent would people go in cloning and might end up exploiting or extinguishing human life for the benefit of the other (fear of the unknown) and also the potential for harmful abuse of the technology might keep us developing more techniques. Risks and uncertainties associated with the current state of cloning technology. They criticized cloning of Dolly saying that it diminishes the chances of natural selection and genetic variability which are the very foundation of species diversity (S. Ignacimuthu; 2009). Since Dolly was the first mammal to be cloned they feared she might have negative effects on the biochemical processes that support ecosystems and might cause changes in the rate and direction of the evolutionary responses of species to each other and their physical and chemical environments.
Diagram 1 : Showing how Dolly the sheep was cloned.
(Source :Prakash S Lohar, Biotechnology; 2005 pg 29)
b) Discuss the techniques that have been applied in producing genetically modified tomatoes and the controversies surrounding the production of GM tomatoes.
A genetically modified tomato is a tomato that has had its genes modified, using techniques in genetic engineering such that it will have incorporated foreign genome in its genetic makeup. The first commercially available genetically modified food was a tomato engineered to have a longer shelf life. Different techniques are used in the production of genetically modified tomatoes. These include:
Recombinant DNA: following steps occur in recombinant DNA technique
- Gene of interest is isolated from the DNA molecule using restriction enzymes. 2) After isolation, gene is inserted into a vector and is cloned to make multiple copies of gene of interest. 3) After cloning the gene is incorporated into the plasmid. 4) Now the gene along with the plasmid is called recombinant DNA
Plasmids and vectors used for recombinant technique are usually bacteria or viruses. They have the ability to carry foreign genes into the host cell where they release the gene of interest and this gene replaces the diseased gene in the tomato plant. Plasmid is a circular piece containing the genetic material. When the new gene is inserted in it, it attaches to the plasmid at the site which will have been cut by the same restriction enzyme with the aid of DNA ligase. The new gene replicates along the plasmid`s genetic material (Prakash S.Lohar).
Lipofection –According to Keogh Jim (2005) makes use of small bubbles of fat called liposomes that are used as the carriers of selected DNA. The target cells and the liposomes are placed into a special solution. The liposomes are placed solution. The liposomes merge with phospholipids in the cell membrane, allowing the DNA entry into the cells for inclusion in the chromosome.
Barnum S.R (1998) says microinjection is a method whereby a foreign gene is integrated into the cell by just injecting it into the recipient cell. In plants like tomatoes, a fine glass needle is used to inject the foreign gene. The inserted genes automatically enter into the nucleus where they incorporate with the host`s cell`s genetic material.
Electro and chemical poration – in this technique pores are created in the membrane of the cell and genes can be transferred easily. Special chemicals are used to make pore in cell surface. Sometimes cells are exposed to weak electric current, it makes pores in the surface of the cells and genes can easily pass through these pores. The selected DNA is exposed to chemical such as calcium phosphates forming tiny granules are then taken up by cells by processes such as endocytosis (http:// www.biotechnology forums.com)
Agrobacterium – agrobacterium is a bacterium that affects plants by altering the genetic makeup of the plants hence making it a suitable carrier for delivering foreign gene into a plant. The bacterium`s cell wall is made porous, recombinant DNA is then added into the solution containing the bacterium. The mixture is heated to allow the plasmid to be taken up by the bacterium. The bacterium is inserted into the tomato plant and it delivers the plasmid and the new gene is expressed in the plant.( Cowan M.K, 2009)
Biolistics method – in this technique gold or silver particles are used to insert the genetic material into the recipient cell. These silver/gold particles are coated with the genetic material and when released in the cell, genetic material incorporates with the genes of the host cell. A short-gun is used bombard the silver and gold particles on the leaves of the plants.
Direct introduction into an organism of heritable genetic material prepared outside the organism by:
- micro-injection,
- macro-injection and
- micro-encapsulation.
- Cell fusion or hybridization techniques by non natural means.
They are controversies surrounding the production of GM tomatoes. As with the Flavr Savr tomato, a source of debate has encompassed the use of antibiotic resistance genes as selectable markers to indicate when an organism has been transformed. These enzymes have the potential to inactivate clinically invaluable antibiotics. Some fear that deleting gens also may introduce harmful side effects when the product is ingested for example; plants produce secondary compounds that may protect them from fungal and bacterial infection. If secondary compounds are removed, people may be exposed to cancer causing compounds produced by fungus (Barnum S.R; 1998).
The release of the first GM food, the Flavr Savr tomato generated much discussion about the potential risks of genetically engineered food. The primary public fear was that a genetically modified plant would produce unexpected results. Plants produce secondary metabolites that may be toxic to humans, although these may be in low concentrations in our food; one fear has been that a GM plant may produce them in higher quantities that may be toxic to humans (Besty Tom and Jim Keogh; 2005). Many people have food allergies that vary from a mild reaction such as a rash to more severe reaction such as anaphylactic shock. There has been concern that the allergenic properties of food from a donor plant might be conferred on the host plant and that people may not be aware that the genetically engineered food contains the new proteins.
Cowan M.K (2009) says that some scientists feared that the release of recombinant DNA plants without risk assessment may disrupt the ecosystem. Viral nucleic acid, inserted into plants to make them resistant to viruses might combine with the genome of an invading virus to make the virus even stronger! Some are concerned that the engineered genes can jump species and have unintended consequences as they spread far afield from the original engineered crop. Others have questioned whether the nutritional quality of genetically engineered foods could change unexpectedly perhaps a particular nutrient may change to a form that cannot be metabolized or absorbed properly. They is also the question of what constitutes true freshness, if a vegetable or fruit looks, feels and tastes fresher and riper is it really just an nutritious as its non-engineered counterpart?
References
- Barnum Susan. R, 1998, Biotechnology: An introduction, New Delhi, Vikas Publishing House.
- Besty Tom and Keogh Jim, 2005, Microbiology demystified, New York; MacGraw-Hill.
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Cowan Majorie Kelly, 2009, Microbiology: A Systems Approach, 3rd edition; New York; MacGraw-Hill.
- Ignacimuthu S.S.J, 2009, Bioethics, Chennai, Alpha Science International Limited.
- Morton Jenkins, 2003, teach yourself genetics, Coventry, Cox Wyman limited
- Prakash S. Lohar, 2005, Biotechnology, Chennai, MJP Publishers.
Websites accessed
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CHINHOYI UNIVERSITY OF TECHNOLOGY
Name Tanyaradzwa R Ngara
Reg Number C1110934J
Course Recombinant DNA Technology
Module Code CUBT 203
Program Biotechnology
Level 2:1
Lecturer Dr Mlambo
Question:
- Dolly the sheep (1996-2003) was the first ever mammal to be cloned from an adult cell. Describe how Dolly was created and discuss why the experiment was widely criticized by some scientists and the general public.
- Discuss the techniques that have been applied in producing genetically modified tomatoes and the controversies surrounding the production of genetically modified tomatoes.