CASE STUDY Golden rice - Riz D'or

Golden rice is a variety of Oryza sativa rice produced through genetic engineering to biosynthesize beta-carotene, a precursor of pro-vitamin A in the edible parts of rice. The scientific details of the rice were first published in Science in 2000. Golden rice was developed as a fortified food to be used in areas where there is a shortage of dietary vitamin A. In 2005 a new variety called Golden Rice 2 was announced which produces up to 23 times more beta-carotene than the original variety of golden rice. Neither variety is currently available for human consumption. Although golden rice was developed as a humanitarian tool, it has met with significant opposition from environmental and anti-globalization activists.

The research that led to golden rice was conducted with the goal of helping children who suffer from vitamin A deficiency (VAD). At the beginning of the 21st century, 124 million people, in 118 countries in Africa and South East Asia, were estimated to be affected by VAD. VAD is responsible for 1–2 million deaths, 500,000 cases of irreversible blindness and millions of cases of xerophthalmia annually. Children and pregnant women are at highest risk. Vitamin A is supplemented orally and by injection in areas where the diet is deficient in vitamin A. As of 1999, there were 43 countries that had vitamin A supplementation programs for children under 5; in 10 of these countries, two high dose supplements are available per year, which, according to UNICEF, could effectively eliminate VAD. However, UNICEF and a number of NGOs involved in supplementation note more frequent low-dose supplementation should be a goal where feasible.

Because many children in countries where there is a dietary deficiency in vitamin A rely on rice as a staple food, the genetic modification to make rice produce provitamin A (beta-carotene) is seen as a simple and less expensive alternative to vitamin supplements or an increase in the consumption of green vegetables or animal products. It can be considered as the genetically engineered equivalent of fluoridated water or iodized salt.

Initial analyses of the potential nutritional benefits of golden rice suggested consumption of golden rice would not eliminate the problems of blindness and increased mortality, but should be seen as a complement to other methods of vitamin A supplementation. Since then, improved strains of golden rice have been developed containing sufficient provitamin A to provide the entire dietary requirement of this nutrient to people who eat about 75g of golden rice per day.

In particular, since carotenes are hydrophobic, there needs to be a sufficient amount of fat present in the diet for golden rice (or most other vitamin A supplements) to be able to alleviate vitamin A deficiency. In that respect, it is significant that vitamin A deficiency is rarely an isolated phenomenon, but usually coupled to a general lack of a balanced diet (see also Vandana Shiva's arguments below). Hence, assuming a bioavailability on par with other natural sources of provitamin A, Greenpeace estimated adult humans would need to eat about 9 kilograms of cooked golden rice of the first breed to receive their RDA of beta-carotene, while a breast-feeding woman would need twice the amount; the effects of an unbalanced (fat-deficient) diet were not fully accounted for. In other words, it would probably have been both physically impossible to grow enough as well as to eat enough of the original golden rice to alleviate debilitating vitamin A deficiency. This claim however referred to a prototype cultivar of golden rice; more recent versions have considerably higher quantities of vitamin A in them.

CASE STUDY B.t. corn - Mais B.t.

Bt-corn is a type of genetically modified organism, termed GMO. A GMO is a plant or animal that has been genetically modified through the addition of a small amount of genetic material from other organisms through molecular techniques. Currently, the GMOs on the market today have been given genetic traits to provide protection from pests, tolerance to pesticides, or improve its quality. Examples of GMO field crops include Bt-potatoes, Bt-corn, Bt-sweet corn, Roundup Ready soybeans, Roundup Ready Corn, and Liberty Link corn.

Genetically modified foods are foods derived from GMO crops. For example, corn produced through biotechnology is being used in many familiar foods, including corn meal and tortilla chips. In addition, corn is used to make high fructose corn syrup, which is used as a sweetener in many foods such as soft drinks and baked goods. While the FDA (U.S. Food and Drug Administration) regulates genetically modified foods, it considers Bt-corn to be nutritionally equivalent to traditional corn.

To transform a plant into a GMO plant, the gene that produces a genetic trait of interest is identified and separated from the rest of the genetic material from a donor organism. Most organisms have thousands of genes, a single gene represents only a tiny fraction of the total genetic makeup of an organism.

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A donor organism may be a bacterium, fungus or even another plant. In the case of Bt corn, the donor organism is a naturally occurring soil bacterium, Bacillus thuringiensis, and the gene of interest produces a protein that kills Lepidoptera larvae, in particular, European corn borer. This protein is called the Bt delta endotoxin. Growers use Bt corn as an alternative to spraying insecticides for control of European and southwestern corn borer.

Bt Delta Endotoxin

The Bt delta endotoxin was selected because it is highly effective at controlling Lepidoptera larvae, caterpillars. It is during the larval stage when most of the damage by European corn borer occurs. The protein is very selective, generally not harming insects in other orders (such as beetles, flies, bees and wasps). For this reason, GMOs that have the Bt gene are compatible with biological control programs because they harm insect predators and parasitoids much less than broad-spectrum insecticides. The Bt endotoxin is considered safe for humans, other mammals, fish, birds, and the environment because of its selectivity. Bt has been available as a commercial microbial insecticide since the 1960s and is sold under many trade names. These products have an excellent safety record and can be used on many crops until the day of harvest.

To kill a susceptible insect, a part of the plant that contains the Bt protein (not all parts of the plant necessarily contain the protein in equal concentrations) must be ingested. Within minutes, the protein binds to the gut wall and the insect stops feeding. Within hours, the gut wall breaks down and normal gut bacteria invade the body cavity. The insect dies of septicaemia as bacteria multiply in the blood. Even among Lepidoptera larvae, species differ in sensitivity to the Bt protein.

 

Genetic Modification

Do Bt-corn hybrids differ only in that they possess the genetic code to produce the Bt protein? Not exactly. To add a trait to a crop plant, the gene must be inserted along with some additional genetic material. This additional genetic material includes a promoter sequence that, in part, determines how the new trait is expressed in the plant. For example, the promoter may cause to protein to be expressed in certain parts of the plants or only during a particular period of time. There is a marker gene that allows plant breeders to easily determine which plants have been transformed. Herbicide and antibiotic tolerance promoters are commonly used to identify transformed plants. There may also be a plasmid or vector sequence that allows for rapid multiplication of the gene of interest in a bacterial host prior to insertion in the crop plant.

FDA Approval

Federal food law requires premarket approval for food additives, whether or not they are the products of biotechnology. FDA treats substances added to food products through recombinant DNA techniques as food additives if they are significantly different in structure, function or amount than substances currently found in food.

However, if a new food product developed through biotechnology does not contain substances that are significantly different from those already in the diet, it does not require premarket approval. Products that are genetically engineered to provide pesticide traits, such as resistance to the corn borer, are also subject to regulation by the Environmental Protection Agency. Currently, genetically modified foods in the United States do not require special labeling to notify consumers.

STUDIU DE CAZ - The first synthetic cell - La premiere cellule synthetique

A chemically synthesised chromosome has for the first time been transplanted into a cell to produce a synthetic bacterium. The advance provides a basis for making organisms designed from scratch and represents a major step towards applications in biofuels and chemical synthesis through synthetic biology.

The man-made microbe is the work of a team led by Dan Gibson and genome sequencing pioneer Craig Venter, at Venter's institutes in Rockville, Maryland and San Diego, California, US. Besides a few genetic 'watermarks' encoded by the team, its genome largely duplicates that of a goat parasite called Mycoplasma mycoides. Grown in a dish, the synthetic version looks much like the original and, like its natural counterparts, is capable of self-replicating.

'For the past 15 years, the genomes of many organisms have been sequenced and deposited in databases. We call this digitising biology,' says Gibson. 'We now show that it is possible to reverse this and synthesise cells starting from this digitised information.' The aim, essentially, is to be able to carry all the information required for making life around on a memory stick.

Actually making it, however, is rather trickier. The M. mycoides genome contains more than a million 'letters' of code - nucleotide base pairs (bp) - but current DNA synthesising technology can only string together a few thousand at once. Thus, Gibson's team exploit the ability of yeast to stitch together small DNA fragments using enzymes. Since announcing the first synthetic genome in 2008,1 they have been attempting to create synthetic life by transferring bacterial genomes assembled in yeast into naturally grown host cells.

In the present study,2 over a thousand short (1,000 bp) pieces of DNA were chemically synthesised and joined by overlapping ends - as Gibson explains, the yeast recognises the overlap in the code and sews them together. Larger segments of first around ten and then a hundred thousand base pairs were combined to produce the full length synthetic genome, which was finally transplanted into the host, another bacterium of the same genus called M. capricolum.

So Gibson's work provides the tools for creating artificial life, but what about the blueprints? Designing an organism from scratch requires an understanding of what each gene codes for. But we're getting there, according to Paul Freemont of the Centre for Synthetic Biology and Innovation at Imperial College London, UK.

'The extrapolation of course is that you could actually design genomes and there's a lot of ground to cover before then, but we do understand quite a lot about what all the genes code for, so I think it's a very major step,' says Freemont. 'More likely would be to try to make a minimal synthetic genome, containing all the basic properties of a living organism, which would allow you to put other types of gene circuits into it, like biofuels or fine chemicals.'