BIOL114 - Lecture 8

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  • Created by: Katherine
  • Created on: 16-03-16 15:48
What are the targets of plant biotechnology?
Agronomic traits, quality traits, novel crop products and biofuels
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What are some features changed in relation to agronomic traits:
Yield, herbicide tolerance, disease and pest resistance e.g. insect resistance, abiotic stress resistance, reproduction
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What are some features changed in relation to quality traits:
Processing, shelf life, nutritional quality (Golden Rice), reduced anti-nutritionals.
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What are some features changed in relation to Novel crop products :
Oils, Proteins: pharmaceuticals, vaccines, polymers: platics
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Which two traits account for the majority of the GM crops currently under cultivation?
Herbicide tolerance (HT) and insect resistance
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What is Glyphosate (Roundup)?
A broad spectrum herbicide made by Monsanto.
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How does Glyphosate work?
It acts by inhibiting a chloroplast enzyme required from aromatic amino acid biosynthesis.
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How was it made?
A mutant EPSP synthase gene was isolated from a bacterium resistant to the herbicide. The gene was introduced into plants to confer resistnace - a simple monogenic trait.
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What are the pros of HT crops?
Enhanced crop productivity, Encourages "no-till" agriculture - reducing soil erosion and lowering fuel costs and greenhouse gas emissions.
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What are the cons of HT crops?
Increased use of Roundup (but reduced use of other herbicides), Possible reduction in biodiversity.
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What is Bacillus thuringiensis?
A soil bacterium whose spores contain a crystalline protein that kills insects.
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What were the spores of Bacillus thuringiensis used for?
Used as a commercial insecticide in 1938 and are still used by organic farmers.
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What is good about the bacillus thuringiensis spores?
They are very specific, the toxin binds to specific receptors in the gut of the target insect - so not toxic to other animals. Environmentally friendly.
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How does Bt work?
Larva consumes toxin, crystals solubilized and toxin activated by proteolytic cleavage in mid gut, Toxin binds to specific receptors, Binding triggers cell death in mid gut lining, septicaemia follows are larva dies.
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How have plants been engineered with the Bt gene?
Different genes target different groups of insects, DNA constructs carrying different cry genes have been introduced into maize, cotton and other crops. One of the most widely grown Bt maize varieties carries the cry1AB gene, which confers resistance
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What is the major pest of maize in the USA?
The european corn borer
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What does the corn borer do?
It causes losses of 1.5 billion kg/year in maize production
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What are the pros of Bt crops?
Reduced financial costs due to less pesticide use, reduced environmental impact of chemical pesticides, improved health of farmers, improved food quality due to reduction in fungal toxins.
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What are the cons of BT crops?
Selection pressure for resistant pests, possible effect on non target insects - controversial idea
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What is special about Golden Rice?
It is a provitamin A enriched rice variety
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What is vitamin A?
Retinol - a pigment of the eye and the acid (retinoic acid) is a growth hormone.
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Where do humans obtain vitamin A from?
Provitamin A from plants enzymatically into vitamin A in the intestine and liver, From animal products containing vitamin A (liver, milk, eggs)
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What is VAD?
Vitamin A deficiency
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What are the symptoms of VAD?
Night blindness, xerophthalmia (dry eyes)
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What is VAD associated with?
Increased susceptibility to death from childhood diseases.
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Why do not more people take vitamin tablets?
Because they are difficult and expensive to administer in developing countries on a large scale.
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What is the main cause of VAD?
The low vitamin A content of the rice grain - polished rice contains little or no B carotene.
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While studying the synthesis of B carotene in daffodils, they found what?
That there are four enyme catalysed steps missing in rice grains
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How did they make a rice that was rich in B carotene?
The two daffofil genes and the Erwinia gene were placed under the control of endosperm specific promoters and introduced into the rice. The resultant transgenic rice lines had enhanced B carotene levels in the endosperm.
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What are the pros of Golden rice?
It has the potential to save millions of children from death or blindness
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What are the cons of Golden Rice?
It reinforces dependence on rice diet - better to increase diversity in agriculture and diet
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What are Aphids?
A major agricultural pest, damaging crops as well as carrying important plant diseases - normally controlled using insecticides.
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What is aphid alarm pheromone?
It is a volatile, non toxic chemical produced by aphids in response to attack. It triggers cessation of feeding an disperal of aphids.
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What is EBF
I
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What does EBF do?
It attracts predators that feed on the aphids
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Transgenic wheat lines have been developed that emit what?
The aphid alarm pheromone
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What do the wheat lines express?
Two codon optimized synthetic genes in their chloroplasts, allowing synthesis of EBF
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What were the synthetic genes that were expressed?
FPP snthase adn EBF synthase
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What is an edible vaccine?
It is the name given to vaccine where the antigen is produced in a transgenic plant and can be administered orally.
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What are the advantages to edible vaccines?
Production is highly efficient and easily scaled up, you do not require refrigeration, it is particularly appropriate for developing countries where the production is expensive.
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What are the steps taken to developing an edible virus for Measles?
Select an antigen (MV-H), Isolate the MV-H gene, express the MV-H gene in an edible transgenic plant. Test effectiveness by feeding the MV-H lettuce to mice. Assay for the presence of anti-MV-H antibodies in mice
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What are the prospects for edible vaccines?
Expression in plants has so far been demonstrated for antigens against cholera ect. An edible vaccine conferring dual immunity has recently been reported for cholera and malaria. At least 3 small scale human trials have shown potential.
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What is the major hurdle to edible vaccines?
The regulatory issues associated with GM crops in general
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Card 2

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What are some features changed in relation to agronomic traits:

Back

Yield, herbicide tolerance, disease and pest resistance e.g. insect resistance, abiotic stress resistance, reproduction

Card 3

Front

What are some features changed in relation to quality traits:

Back

Preview of the front of card 3

Card 4

Front

What are some features changed in relation to Novel crop products :

Back

Preview of the front of card 4

Card 5

Front

Which two traits account for the majority of the GM crops currently under cultivation?

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