19.3. Genetically modified organisms in agriculture Flashcards
Significance of Genetic Engineering
- improving the quality and yield of crop plants and livestock in solving the demand for food in the world
- proteins for use in medicine can be produced from
genetically modified plants, so avoiding any problem of
contamination by animal proteins - examples include vaccines, albumin and the proteins found in breast milk that are used to treat diarrhoea in infants.
Herbicide Resistant Crops
- Growing a herbicide-resistant crop allows fields to be sprayed with herbicide after the crop has germinated, killing any weeds that would otherwise compete with the crop for space, light, water or ions.
- This increases the yield of the crop.
- Oilseed rape and tobacco
- In both cases the genes were taken from other species of plant.
Oilseed Rape - Herbicide Resistance
- grown for the oil that can be extracted from its seeds
- used in food production, and also to produce biofuels and lubricants
- GM varieties of oilseed rape contains genes that make it resistant to the herbicide glyphosate
- glyphosate inhibits an enzyme involved in the synthesis of three amino acids, which is absorbed by a plant’s leaves and is transported to the growing tips.
- the amino acids are needed for producing essential proteins, so the plant dies.
- farmers can spray glyphosate, killing the weeds and not the oilseed rape
- this increases yield and reduces costs
Effects of Herbicide Resistant Crops
- the genetically modifed plant will become an agricultural weed
- pollen will transfer the gene to wild relatives,
producing hybrid ofspring that are invasive weeds - herbicide-resistant weeds will evolve because so much
of the same herbicide is used.
Insect-resistant crops
- Maize is protected against the corn borer
- Cotton is protected against pests such as the boll weevil
- In both plants, yield is improved
- Insect-resistant tobacco also exists, and is protected
against the tobacco bud worm, but as yet it has not been grown commercially. - A gene for a toxin, Bt toxin, which is lethal to insects
that eat it but harmless to other animals, has been taken
from a bacterium, Bacillus thuringiensis. - Crop plants that contain the Bt toxin gene from B. thuringiensis produce their own insecticides.
Advantages of Insect-resistant crops
- less loss of the crop to inset pests, so greater yields are obtained
- less or no insecticide is needed to be sprayed, reducing harm to non-target insect species
- only insects that eat the plants are harmed, not others
- less likely that pests will develop resistance than to pesticides. however, insects still can
Detrimental effects of Insect-resistant crops
- the evolution of resistance by the insect pests
- a damaging effect on other species of insects
- the transfer of the added gene to other species of plant (no evidence yet)
- seed of Bt corn and cotton costs more for farmers to buy than non-GM seed, making it difficult for farmers in developing countries to afford it, so it is more difficult to compete with farmers in developed countries
Golden Rice
- rice that has genes encoding vitamin A added to it
- in countries where rice forms a major part of the diet, children suffer from vitamin A deficiency, causing blindness and immune deficiency syndrome
- eating this GM rice provides more B carotene, which is used to make vitamin A
- companies and researchers who developed the rice have donated it free for use in developing countries
- not yet allowed to be grown for farmers
- not known about GM crops effect on health
Golden Rice Production Process
1) Genes for the production of carotene were extracted
from maize and the bacterium Pantonoea ananatis.
2) These genes, together with promoters, were inserted into plasmids.
3) The plasmids were inserted into bacteria called Agrobacterium tumefaciens.
4) These bacteria naturally infect plants and so could
introduce the genetically modifed plasmid into rice
cells. They were mixed with rice embryos in Petri dishes,
some of which were infected by the bacteria carrying the carotene genes.
5) The rice embryos, now containing the carotene genes, were grown into adult plants. They produced seeds containing carotene in their endosperm.
GM Salmon
- a company in USA has developed a GM variety of salmon that contains a growth hormone gene from another species of salmon, and a promoter from a different species of fish
- this makes the GM salmon grow way faster and larger than normal
- this could allow food to be produced more quickly
- however, there are concerns if the fish escape, they could reproduce in the wild and adversely affect populations of other marine organisms
- to avoid these problems, it is planned to only farm sterile female fish
- GM salmon are also all triploid, making it difficult for them to produce viable gametes
Ethical and Social Implications of using genetically modified organisms (GMOs) in food production
Concerns
- The modified crop plants may become agricultural
weeds or invade natural habitats.
- The introduced gene(s) may be transferred by pollen
to wild relatives whose hybrid offspring may become
more invasive.
- The introduced gene(s) may be transferred by pollen
to unmodified plants growing on a farm with organic
certification.
- The modified plants may be a direct hazard to humans,
domestic animals or other beneficial animals, by being
toxic or producing allergies.
- The herbicide that can now be used on the crop will
leave toxic residues in the crop.
- Genetically modified seeds are expensive, as is
herbicide, and their cost may remove any advantage of
growing a resistant crop.
- Growers mostly need to buy seed each season, keeping costs high, unlike for traditional varieties, where the grower kept seed from one crop to sow for the next.
- Danger of losing traditional varieties with their desirable background genes for particular localities and their possibly unknown traits that might be useful in a world where the climate is changing.
