Benefits of a Genetically Enhanced Pig
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How successful would the Enviro-pig be if released into the general pig population in terms of longevity of the trait and continued benefits to the environment? And do the ethical issues stacked against the Enviro-pig validate its modified presents in the genepool?
DNA is the foundation of all genetic material found in every living organism on earth. Commonly known as its full name Deoxyribonucleic acid, it is an electrically neutral group of atoms held together in a chemical bond known as a molecule. In this case a biomolecule produced by a living organism composed of nucleic acid, carbohydrates and proteins. This mixture is coiled in twobiopolymer strands forming adouble helix. Biopolymers being a biomolecule of a polymer, which is a large molecule, composed of monomers. These biopolymer strands are composed of thirteen nucleotide monomers bonded in a chain, in turn called a polynucleotide. Nucleotides being singular polynucleotides composed of a nucleobase (containing nitrogen). Being split into four bases each nucleobase is as followed:
- Guanine (C5H5N5O): Pairing in sequence with cytosine, guanine is derived from purine. Purine is an organic compound structured from a pyrimidine ring fused to an imidazole ring (called a pyrimidine-imidazole ring). The base is represented as ‘G’.
- Adenine (C5H5N5): Similar to that of Guanine, Adenine is derived from purine. In addition it’s an important part of adenosine triphosphate (ATP). ATP is the nitrogenous base adenine bonded to a five carbon sugar. These molecules have the ability to phosphorylise and add phosphate groups to other molecules. This allocation of phosphates allows energy to be released. It is this energy which is used in the cells of living organisms. The base is represented as ‘A’.
- Thymine (C5H6N2O2): Combining with Adenine this nucleobase is often replaces with uracil in RNA. It is also the common cause of mutations in DNA. When in the presence ofultraviolet light, radiation causes alterations in the DNA molecule that inhibit normal function. These “kinks” are referred to as pyrimidine dimers. The base is represented as ‘T’.
- Cytosine (C4H5N3O): Pairing with guanine this base is a pyrimidine derivative. A heterocyclic aromatic ring that when as cytosine triphosphate (CTP) can performance as a co-factor to enzymes, able to transfer a phosphate to transfigure adenosine diphosphate (ADP) to adenosine triphosphate (ATP).
Nucleotides of a DNA stand line up so each sugar and phosphate molecule connects. As said an adenine only pairs with a thymine and a cytosine only pairs with a guanine. The sugars are linked together by phosphate clusters via phosphodiester bonds, branching between adjacent sugar rings. The dual helix is stabilized by the bases of hydrogen bonds, before bunching together and constricting a vase line of rungs. All are curled together with multiple strands to form a chromosome. Being such a delicate sequence of codes, all of which contributing towards every characteristic in an organism, if altered or affect in a minor way a secession of errors and mutations can occur. Mutation is when an alteration of a nucleotide arrangement in the genome causes changes in an organism. Even if by a small change, the structural integrity of a creature can differ. But if this large sequence of coding is only effect in one base, in one strand, located in a single cell, the error theoretically should not affect the creature. However through Protein synthesis and mitosis a fault can replicate and spread.
Protein synthesis is the process of cells building proteins. The term is a multi-step process, commencing with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then used as input to translation. Transcription is when one biopolymer is taken from the other and used as a template to construct an identical RNA chain. Once replicated this messenger RNA (mRNA) moves to the surrounding cytoplasm outside the nucleus which commences the second stage know as translation. However when the mRNA migrates to the cytoplasm it is spliced, leaving only the nucleotides being coded. These are referred to codons. During stage two ribosomes bind to the mRNA (commonly to start codons) manufacturing the sugar and phosphate bonds codon by codon (amino acids are added one by one) until all rungs have connected creating a protein. Afterwards the completed polypeptide detaches from the ribosome. This process is repeated multiple times before mitosis commences to form an identical cell. Referring back to a fault occurring in a nucleotide codon, this error will undergo protein synthesis and mitosis, creating a sequence containing the mutation. Such a mutation affecting the sequence in four main ways:
- Substitution – During coding a base is exchanged for another, hence altering a codon that encodes a different amino acid, changing the protein produced. This codon can also change to the same amino acid rendering the same protein produced (silent mutation) as well as coding a “stop” causing an incomplete protein.
- Insertion – This occurs when a base is ‘inserted’ which would result in similar issues as Substitution.
- Deletion – A base is lost or essentially ‘deleted’ also resulting in similar issues.
- Frame shift – Since each codon is dived into three nucleobases and through insertions and deletions the message of the protein is no longer correct. This is known as frame shift.
All of these genetic processes when related to modern day science can result in a positive or negative outcome. Upon understanding these processes of mutation and cell replication it allows for Induced mutations as opposed to natural mutations occurring over millions of years. Ranging from plants being immune to pesticides to animals glowing in the dark, a great example of genetic ingenuity is the Enviro-pig. Created by a recombinant DNA process of pronuclear microinjection to create a transgenic organism. In this case a breed of Yorkshire pigs developed at the University of Guelph in Ontario, Canada, was genetically altered to allow for the breaking down of phosphate in the digestion process of the swine. This was achieved through the microinjection of a transgene construct, as referred to by http://www.uoguelph.ca/enviropig/technology.shtml
‘The Enviropig™ was developed by the introduction of a transgene construct composed of the promoter segment of the murine parotid secretory protein gene and the Escherichia coli phytase gene (Golovan et al 2001) into a fertilized porcine embryo by pronuclear microinjection.’
The Enviro-pig along with many altered organism were objected too due to social, economic and religious concerns surrounding the transgene engineering. Upon the birth of the Yorkshire piglets however analysis showed the trait rendered no difference in the meat or overall health of the animal. The extracted phytase through examination was 99% identical to the commercially approved phytase given as supplements in the diets of average farmed pigs. Furthermore 80% of the offspring produced held the gene (refer to Monohybrid Cross) allowing the silverly glands of the pigs to secrete phytase which would break down phosphate in food.
The promoter slice of murine parotid secretory protein gene and the E. coli phytase gene accountable for the ‘modification’ in the swine highlighted the environmental impacts of existing Yorkshire pigs. The whole alteration was artificial induced due to the diet of average factory farmed pigs. As mentioned above ‘the gene allowed the silverly glands of the pigs to secrete phytase which would break down phosphate in food.’ Approximately 50-75% of the phosphorus present in corn, soybeans and cereal grains given to pigs are found in the indigestible compound phytate, causing it to not be broken down and move through the body. The phosphate is enriched due to carbohydrates and organic exchanges through digestion hence the manure is high in the chemical. When manure from ordinary pigs is spread throughout land in areas surrounding intense swine production, it has been shown that there is an accumulation of phosphorus in the soil. Upon heavy rain this rich soil runs into water ways, increasing the phosphorus concentration of the water. The chemical composure creates the ideal conditions for algae to grow, layering the body of water causing a reduction in oxygen concentration. Resulting in the death of fish and other aquatic animals. The ecosystem of the area is effect, removing food for birds and killing plant life. On top of this alga produces toxins resulting in the water to be undrinkable. Branching out from these facts the enviro-pigs creation proves to be an environmental benefit, but as not all people agree.
Though producing manure with 25-30% less phosphorus the benefits of the Enviro-pig as outlined on http://documents.foodandwaterwatch.org/doc/Enviropig.pdf may seem only valid to pigs held in factory farms.
‘The only setting in which Enviropig’s unique new trait offers any utility is on a factory farm. The factory farm model of raising pigs is so detrimental to the environment (Paragraph 4)……..the actual amount of waste that the Enviropig produces is not reduced in any meaningful way; the chemical makeup of the waste is just modified……and finally According to the U.S. Department of Agriculture (USDA). Only 20 to 50 percent of all large hog farms have enough land on which to spread all their manure without exceeding limits on phosphorus or nitrogen application. Because of its danger to humans and the environment, phosphorous is one of the major nutrients monitored in U.S. Environmental Protection Agency CAFO regulations.’ (Golovan, Serguei, et al. “Pigs expressing salivary phytase produce low phosphorus manure.” Nature Biotechnology, vol.19. 2001 at 741.)
With these statements outlined, the environment ‘benefits’ of the genetically enhanced pig seemed only in place for pigs of a specific role, as opposed to pigs in other farming industries. If only concerned with factory pigs, reducing the phosphorus content of soil surrounded areas of factory farming the ‘pros’ of the pig is limited in relation to the rest of the environment. Opening up the validity of the focus question established. If a Yorkshire pig was injected with the trait and mated with an ordinary pig, would the ‘longevity’ of the trait last through multiple generations of crossbreeding? After all genetically altered organisms can have a positive or negative impact. Natural ecosystems can be disturbed or altered, further mutations causing deformities which in turn affect the way of life of the animal in contrast to requiring less food, growing quicker, and in this case leave behind a smaller amount of environmentally damaging waste as well as producing leaner meat, be more resilient to harmful and painful diseases and to reproduce at a faster rate. But from this concept monohybrid and dihydrid crosses were established for the enviro-pig (Refer to ) which was than constructed into a pedigree tree.
[Explain findings from crosses and future generation in relation to past]
Refer to Glossary for words in BoldPage 1
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