GM plants and animals I – GM Food Flashcards
Genetic engineering of foodhas
revolutionized agriculture
An example of GM food is
Maize
maize yields have increased four-fold over the last 60 years, and more than half of this increase is due to genetic improvement by artificial selection and selective breeding
Maizes original ancestor
Teosinte
Selective breeding
select and breed naturally occurring or mutagen-induced variants of crops
Worldwide, millions of acres of genetically engineered crops have been planted, particularly herbicide-and pest-resistant soybeans, corn, cotton, and canola; over 50 different transgenic crop varieties are available, including alfalfa, corn, rice, potatoes, tomatoes, tobacco, wheat, and cranberries.
Agricultural biotechnology is useful to
■ Improve the growth characteristics and yield of agriculturally valuable crops ■ Increase the nutritional value of crops
■ Provide crop resistance against herbicides (the most widely used application of genetically modified crop plants), insects (insect resistance is the second leading application), viruses, and drought.
GM foods are derived from ___________ specifically plants and animals of agricultural importance.
genetically modified organisms (GMOs),
GMOs are defined as
organisms whose genomes have been altered in ways that do not occur naturally.
GMOs genomes are modified using
recombinant DNA technologies.
Genetic engineering allows
one or more genes to be cloned and transferred from one organism to another - either between individuals of the same species or between those of unrelated species.
When genes are transferred between unrelated species, the resulting organism is called
transgenic.
The term cisgenic is used to describe gene transfers
within a species or from a sexually-compatible species
Although many see potential for GM foods - to help address malnutrition in a world with a growing human population and climate change - others question the technology, oppose GM food development, and sometimes resort to violence to stop the introduction of GM varieties
Pre-genetic engineering era…
Maize
Wheat
Rice
the first commercial GM food
The FLAVR SAVR™ tomato
The FLAVR SAVR™ tomato
produced in the 1980s by Calgene by silencing the polygalacturonase gene for extended shelf-life.
GM food crops
Major crops: maize, soybean, cotton, canola.
Major traits: herbicide and insect resistance.
SA 9th largest grower of commercial GM crops.
In SA, only three commercial GM crops – maize, soybean and cotton.
GMOs are defined as
organisms whose genomes have been altered in ways that do not occur naturally. Typically, their genomes are modified using recombinant DNA technologies.
Genetic engineering allows ________ genes to be cloned and ________ from one organism to another - either between individuals of the same species or between those of unrelated species.
one or more
transferred
GM food crops – top five!
The most widely planted GM crops – approx. 70%!
Herbicide-Resistant GM Crops
Monsanto developed the broad-spectrum herbicide,
Roundup
Roundups active ingredient
Glyphosate
Glyphosate
(Roundups active ingredient)
is effective at low concentrations, is degraded rapidly in soil and water, and is not toxic to humans
However, evidence also suggests that some weeds may be developing resistance to glyphosate,
thereby reducing the effectiveness of glyphosate-tolerant crops.
A bacterial gene (epsps)
confers tolerance to the broad-spectrum herbicide glyphosate have been engineered into many crop plants.
Second most prevalent GM crops are
Bt crops
(Bacillus thuringiensis)
GM crops with insect resistance are mostly
Bt crops
Bt crops. Bacillus thuringiensis (Bt)
is group of soil-dwelling bacterial strains that produce crystal (Cry) proteins that are toxic to certain species of insects. These Cry proteins are encoded by the bacterial cry genes. The Cry proteins are toxic to insects
Cry proteins specific for
Lepidoptera, Diptera, Hymenoptera and Coleoptera.
Insects ingest the crystal toxins,
which are processed by insect proteases into mature toxins that bind to specific receptors on the gut wall, and dissolve the gut membranes to eventually kill the insect.
Gut receptors will be bound by only one of more than 200 different Cry proteins
– thus very specific.
Cry proteins have been used in conventional formulations for many years – also by ‘organic’ growers.
GM crops express Bt genes to produce endogenous crystal proteins,
which will kill specific insect pests, when they feed on such plants.
To create Bt crops
scientists introduce one or more cloned cry genes into plant cells. The GM crop plants will then manufacture their own Bt Cry proteins, which will kill the target pest species when it eats the plant tissues. Although Bt crops have been successful in reducing crop damage, increasing yields, and reducing the amounts of insecticidal sprays used in agriculture, they are also controversial.
Most GM crops have been designed to help farmers increase yields.
However, most are not
consumed directly by humans, but are used as animal feed or as sources of processed food ingredients such as oils, starches, syrups, and sugars.
A single bowl (150 g) of golden rice provides
all of the daily requirement of Vit A.
Golden rice was designed to produce _______, a Vit A precursor.
Created by:
b-carotene
expressing two transgenes, one from a bacterium and one from maize, in rice.
