Mar 10, · Genome sequencing has given rise to a new generation of genetically engineered bioweapons carrying the potential to change the nature of modern warfare and defense. Introduction. Biological weapons are designed to spread disease among people, plants, and animals through the introduction of toxins and microorganisms such as viruses and bacteria How To Stop Poisoning Yourself The Pure & Natural Way: A Guide To Avoiding Processed, Commercialized, Irradiated & Genetically Engineered Food And Products|Secretarius MEMPS Publication We are a life-saving service for procrastinators! Our qualified experts dissertation writers excel at speedy writing and can craft a perfect paper within the shortest deadline Mar 09, · In a recent interview for New York magazine’s Grub Street, author and food activist Michael Pollan laid out why he believes that food containing genetically modified ingredients (GMOs) should be labeled – and why GMO crops have been bad for the environment. “GMOs have been, I think, a tremendous disappointment,” Pollan said. “They haven't done what Monsanto promised they would
GMO Argumentative Essay Examples - Free Persuasive Essays and Research Papers About GMO Foods
NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health, genetically engineered food essay. National Research Council US Committee on Identifying and Assessing Unintended Effects of Genetically Engineered Foods on Human Health. Safety of Genetically Engineered Foods: Approaches to Assessing Unintended Health Effects.
Washington DC : National Academies Press US ; This chapter provides a brief description of genetic modification methods used to develop new plant, animal, and microbial strains for use as human food. The next chapter Chapter 3 presents a detailed analysis of the likelihood for these methods to result in unintentional compositional changes. Modification to produce desired traits in plants, animals, and microbes used for food began about 10, years ago. These changes, along with natural evolutionary changes, have resulted in common food species that are now genetically different from their ancestors.
Advantageous outcomes of these genetic modifications include increased food production, reliability, and yields; enhanced taste and nutritional value; and decreased losses due to various biotic and abiotic stresses, such as fungal and bacterial pathogens. These objectives continue to motivate modern breeders and food scientists, who have designed newer genetic modification methods for identifying, genetically engineered food essay, selecting, and analyzing individual organisms that possess genetically enhanced features.
For plant species, it can take up to 12 years to develop, evaluate, and release a new variety of crop in accordance with international requirements, which specify that any new variety must meet at least three criteria: it must be genetically distinct from all other varieties, it must be genetically uniform through the population, and it must be genetically stable UPOV, While advances in modification methods hold the potential for reducing the time it takes to bring new foods to the marketplace, an important benefit of a long evaluation period is that it provides opportunities for greater assurance that deleterious features will be identified and potentially harmful new varieties can be eliminated before commercial release.
As discussed more fully in Chapter 5it is both prudent and preferable to identify potentially hazardous products before they are made commercially available, and with few exceptions standard plant genetically engineered food essay practices have been very successful in doing so. The easiest method of plant genetic modification see Operational Definitions in Chapter 1used by our nomadic ancestors and continuing today, is simple selection, genetically engineered food essay.
The others are eaten or discarded. The seeds from the superior plants are sown to produce a new generation of plants, all or most of which will carry and express the desired traits. Over a period of several years, these plants or their seeds are saved and replanted, genetically engineered food essay, which increases the population of superior plants and shifts the genetic population so that it is dominated by the superior genotype.
This very old method of breeding has been genetically engineered food essay with modern technology. Genetically engineered food essay example of modern methods of simple selection is marker-assisted selection, which uses molecular analysis to detect plants genetically engineered food essay to express desired features, such as disease resistance to one or more specific pathogens in a population. Superior traits are those considered beneficial to humans, as well as to domesticated animals that consume a plant-based diet; they are not necessarily beneficial to the plant in an ecological or evolutionary context.
Often traits considered beneficial to breeders are detrimental to the plant from the standpoint of environmental fitness. For example, the reduction of unpalatable chemicals in a plant makes it more appealing to human consumers but may also attract more feeding by insects and other pests, making it less likely to survive in an unmanaged environment.
As a result, cultivated crop varieties rarely establish populations in the wild when they escape from the farm. Conversely, some traits that enhance a plant's resistance to disease may also be harmful genetically engineered food essay humans. Crossing occurs when a plant breeder takes pollen from one plant and brushes it onto the pistil of a sexually compatible plant, producing a hybrid that carries genes from both parents.
When the hybrid progeny reaches flowering maturity, it also may be used as a parent. Plant breeders usually want to combine the useful features of two plants. For example, they might add a disease-resistance gene from one plant to another that is high-yielding but disease-susceptible, while leaving behind any undesirable genetic traits of the disease-resistant plant, such as poor fertility and seed yield, susceptibility to insects or other diseases, or the production of antinutritional metabolites.
Because of the random nature of recombining genes and traits in crossed plants, breeders usually have to make hundreds or thousands of hybrid progeny to create and identify those few that possess useful features with a minimum of undesirable features. For example, the majority of progeny may show the desired disease resistance, but unwanted genetic features of the disease-resistant parent may also be present in some. Crossing is still the mainstay of modern plant breeding, but many other techniques have been added to the breeders' tool kit.
Interspecies crossing can take place through various means. Closely related species, such as cultivated oat Avena sativa and its weedy relative wild oat Avena fatua genetically engineered food essay, may cross-pollinate for exchange of genetic information, although this is not generally the case.
Genes from one species also can naturally integrate into the genomes of more distant relatives under certain conditions. Some food plants can carry genes that originate in different species, transferred both by nature and by human intervention. For example, common wheat varieties carry genes from rye. A common potato, Solanum tuberosumcan cross with relatives of other species, such as S. acaule Kozukue et al, genetically engineered food essay. chacoense Sanford et al. Chromosome engineering is the term given to nonrecombinant deoxyribonucleic acid rDNA cytogenetic manipulations, in which portions of chromosomes from near or distant species are recombined through a natural process called chromosomal translocation.
Searspioneered the human exploitation of this process, which proved valuable for transferring traits that were otherwise unattainable, such as pest or disease resistance, into crop species.
However, because transferring large segments of chromosomes also transferred a number of neutral or detrimental genes, the utility of this technique was limited.
Recent refinements allow plant breeders to restrict the transferred genetic material, focusing more on the gene of interest Lukaszewski, As a result, chromosome engineering is becoming more competitive with rDNA technology in its genetically engineered food essay to transfer relatively small pieces of DNA.
Several crop species, such as corn, soybean, rice, barley, and potato, have been improved using chromosome engineering Gupta and Tsuchiya, Sometimes human technical intervention is required to complete an interspecies gene transfer, genetically engineered food essay. Some plants will cross-pollinate and the resulting fertilized hybrid embryo develops but is unable to mature and sprout. Modern plant breeders work around this problem by pollinating naturally and then removing the plant embryo before it stops growing, placing it in a tissue-culture environment where it can complete its development.
Such embryo rescue is not considered genetic engineering, and it is not commonly used to derive new varieties directly, but it is used instead as an intermediary step in transferring genes from distant, sexually incompatible relatives through intermediate, partially compatible relatives of both the donor and recipient species. Recent advances in tissue-culture technologies have provided new opportunities for recombining genes from different plant sources.
In somatic hybridization, a process also known as cell fusion, cells growing in a culture medium are stripped of their protective walls, usually using pectinase, cellulase, and hemicellulase enzymes. These stripped cells, called protoplastsare pooled from different sources and, genetically engineered food essay, through the use of varied techniques such as electrical shock, are fused with one another.
When two protoplasts fuse, the resulting somatic hybrid contains the genetic material from both plant sources. This method overcomes physical barriers to pollen-based hybridization, but not basic chromosomal incompatibilities.
If the somatic hybrid is compatible and healthy, it may grow a new cell wall, begin mitotic divisions, and ultimately grow into a hybrid plant that carries genetic features of both parents. While protoplast fusions are easily accomplished, as almost all plants and animals have cells suitable for this process, relatively few are capable of regenerating a whole organism, and fewer still are capable of sexual reproduction.
This non-genetic engineering technique is not common in plant breeding as the resulting range of successful, fertile hybrids has not extended much beyond what is possible using other conventional technologies.
Somaclonal variation is the name given to spontaneous mutations that occur when plant cells are grown in vitro. For many years genetically engineered food essay regenerated from tis-sue culture sometimes had novel features. It was not until the s that two Australian scientists thought this phenomenon might provide a new source of genetic variability, genetically engineered food essay, and that some of the variant plants might carry attributes of value to plant breeders Larkin and Scowcroft, Through the s plant breeders around the genetically engineered food essay grew plants in vitro genetically engineered food essay scored regenerants for potentially valuable variants in a range of different crops.
New varieties of several crops, such as flax, were developed and commercially released Rowland et al. Molecular analyses of these genetically engineered food essay varieties were not required by regulators at that time, nor were they conducted by developers to ascertain the nature genetically engineered food essay the underlying genetic changes driving the variant features. Somaclonal variation is still used by some breeders, particularly in developing countries, but this non-genetic engineering technique has largely been supplanted by more predictable genetic engineering technologies.
Mutation breeding involves exposing plants or seeds to mutagenic agents e. The breeder can adjust the dose of the mutagen so that it is enough to result in some mutations, but not enough to be lethal, genetically engineered food essay.
Typically a large number of plants or seeds are mutagenized, grown to reproductive maturity, and progeny are derived. The progeny are assessed for phenotypic expression of potentially valuable new traits, genetically engineered food essay. As with somaclonal variation, the vast majority of mutations resulting from this technique are deleterious, and only chance determines if any genetic changes useful to humans will appear.
Other than through varying the dosage, there genetically engineered food essay no means to control the effects of the mutagen or to target particular genes or traits. The mutagenic effects appear to be random throughout the genome and, even if a useful mutation occurs in a particular plant, deleterious mutations also will likely occur.
Once a useful mutation is identified, breeders work to reduce the deleterious mutations or other undesirable features of the mutated plant. Nevertheless, crops derived from mutation breeding still are likely to carry DNA alterations beyond the specific mutation that provided the superior trait. Induced-mutation crops in most countries including the United States are not regulated for food or environmental safety, and breeders generally do not conduct molecular genetic analyses on such crops to characterize the mutations or determine their extent.
Consequently, it is almost certain that mutations other than those resulting in identified useful traits also occur and may not be obvious, remaining uncharacterized with unknown effects. In the United States, crop varieties ranging from wheat to grapefruit have been mutated since the technique was first used in the s.
There are no records of the molecular characterizations of these mutant crops and, in most cases, no records to retrace their subsequent use. Several commercial crop varieties have been developed using cell selection, including varieties of soybeans Sebastian and Chaleff,canola Swanson et al.
The cells are then excised and grown in culture. Initially the population is genetically homogeneous, but changes can occur spontaneously as in somaclonal variation or be induced using mutagenic agents. Cells with a desired phenotypic variation may be selected and regenerated into a whole plant, genetically engineered food essay.
For example, adding a suitable amount of the appropriate herbicide to the culture medium may identify cells expressing a novel variant phenotype genetically engineered food essay herbicide resistance. In theory, all of the normal, susceptible cells will succumb to the herbicide, but a newly resistant cell will survive and perhaps even continue to grow. An herbicide-resistant cell and its derived progeny cell line thus can be selected and regenerated into a whole plant, genetically engineered food essay, which is then tested to ensure that the phenotypic trait is stable and results from a heritable genetic alteration.
In practice, many factors influence the success of the selection procedure, and the desired trait must have a biochemical basis that lends itself to selection in vitro and at a cellular level. Breeders cannot select for increased yield in cell cultures because the cellular mechanism for this trait is not known. The advantage of cell selection over conventional breeding is the ability to inexpensively screen large numbers of cells in a petri dish in a short time instead of breeding a similar number of plants in an expensive, large field trial conducted over an entire growing season.
Like somaclonal variation, cell selection has largely been superceded by recombinant technologies because of their greater precision, higher rates of success, and fewer undocumented mutations, genetically engineered food essay. As noted in Chapter 1this report defines genetic engineering specifically as one type of genetic modification that involves an intended targeted change in a plant or animal gene sequence to effect a specific genetically engineered food essay through the use of rDNA technology.
A variety of genetic engineering techniques are described in the following text. Agrobacterium tumefaciens is a naturally occurring soil microbe best known for causing crown gall disease on susceptible plant species. It is an unusual pathogen because when it infects a host, it transfers a portion of its own DNA into the plant cell.
The transferred DNA is stably integrated into the plant DNA, and the plant then reads and expresses the transferred genes as if they were its own, genetically engineered food essay. The transferred genes direct the production of several substances that mediate the development of a crown gall. Among these substances is one or more unusual nonprotein amino acids, called opines. Opines are translocated throughout the plant, so food developed from crown gall-infected plants will carry these opines.
In the early s strains of Agrobacterium were developed that lacked the disease-causing genes but maintained the ability to attach to susceptible plant cells and transfer DNA.
By substituting the DNA of interest for the genetically engineered food essay gall disease-causing DNA, scientists derived new strains of Agrobacterium that deliver and stably integrate specific new genetic material into the cells of target plant species.
Genetically Modified Foods and Their Pros And Cons
, time: 9:42Genetically engineered foods: MedlinePlus Medical Encyclopedia
Simple Selection. The easiest method of plant genetic modification (see Operational Definitions in Chapter 1), used by our nomadic ancestors and continuing today, is simple blogger.com is, a genetically heterogeneous population of plants is inspected, and “superior” individuals—plants with the most desired traits, such as improved palatability and yield—are selected for continued Aug 10, · by Megan L. Norris Summary: As the prevalence of genetically modified organisms (GMOs) continues to rise, there has been an increasing public interest for information concerning the safety of these products. Concerns generally focus on how the GMO may affect the environment or how it may affect the consumer. One specific concern is the possibility for GMOs to negatively affect human Oct 16, · Food essays are an excellent way to demonstrate your awareness of the topics of health issues and their relationship with nutrition. Obesity is a significant concern that is present in many people throughout the world and can lead to a variety of deadly conditions
No comments:
Post a Comment