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Blueprint of Life Topic 23: Transgenic Species

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1 Blueprint of Life Topic 23: Transgenic Species
Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis

2 DOT POINT(s) outline the processes used to produce transgenic species and include examples of this process and reasons for its use

3 Introduction Biotechnology is any technique that uses living organisms to make products. As far back in recorded history as biblical times, biotechnology was used. For example, yeast was used to bake bread and for the fermentation of wine and the production of cheese.

4 Introduction People in ancient times were unaware that they were employing what we call biotechnology. It was only when Louis Pasteur discovered (in 1862) that fermentation is caused by microorganisms and is not an inorganic chemical process that people became aware that they were using living things to make everyday products.

5 Introduction In modern times, biotechnology has come to be associated with genetic modification (genetic engineering) of living organisms. Modern biotechnology involves manipulating the DNA (genetic material) of living organisms, to artificially combine specific qualities of different organisms.

6 Introduction It is an advancement on the reproductive technologies that we have already discussed, as it allows specific desirable genes to be moved from one species to another. Genes can be ‘cut and pasted’— removed from the cells of one organism and inserted into the genome of another organism, where they become part of the new organism’s genetic make-up and are passed on to its offspring. This has only become possible with an advance in the scientific understanding of the structure and functioning of DNA.

7 Transgenics A transgenic organism is one whose normal genome has been altered by introducing a gene from another species (transgene) into it in such a way that the organism can pass on this transgene to its offspring during reproduction.

8 Transgenics The creation of transgenic species has many applications, including: creating genetically modified foods with increased nutrients, higher yields and which can be processed more easily introducing resistance to disease, pests and pesticides in species treating disease reproductive technology Note: Creation of transgenic species is considered to be a reproductive technology only in cases where it increases the breeding success of the individuals.

9 Transgenics When an organism is genetically modified, this usually entails adding a desirable gene to its DNA. Ideally, one would like to ensure that when it reproduces, it passes this gene on to its offspring, along with all of its other genes. The latter involves the process of genetic engineering to create a transgenic species.

10 Simplified steps outlining how to create a transgenic species
Handout The simplified explanation is ‘cut, copy and paste’ ‘cut’: a gene for a favourable characteristic is removed from the cell of an organism, using restriction enzymes ‘copy’: multiple copies are made (called ‘gene cloning’)— this step is usually carried out in bacteria ‘paste’: the genes are inserted (injected) into an egg cell of another species and after fertilisation become part of the newly formed organism’s DNA The egg develops into a mature organism (a transgenic species) with the new gene ‘switched on’ to function.

11 Gene Delivery Techniques
There are four main ways of inserting the desired gene into the genome of a species to be genetically transformed: 1. micro-injection of DNA directly into the nucleus of a single cell—this is usually performed under an optical microscope to introduce DNA into egg cells when creating transgenic Species.

12 Gene Delivery Techniques
2. biolistics: methods of mechanically delivering DNA on microscopic particles into target tissues and cells by ‘firing’ them from a gene ‘gun’; e.g. tiny gold particles are used to coat the DNA, which is then fired at the target cells under high pressure or voltage by a gene gun.

13 Gene Delivery Techniques
3. electroporation: increasing the membrane permeability by applying an electrical current

14 Gene Delivery Techniques
4. transduction by a viral vector: DNA may be carried by vectors such as an adenovirus, liposomes or bacterial plasmids into cells. These viral vectors may be injected directly into the bloodstream or may be delivered by aerosol delivery (nasal spray or oral aerosol for example, used in trials of gene therapy for cystic fibrosis).

15 Evidence A gene for a fluorescent protein from jellyfish is now used to determine whether an individual has successfully incorporated a transgene. The fluorescent gene is used as a marker and is attached to the desired gene that will be inserted into prospective transgenic organisms. The gene with attached marker is injected into an egg cell and the resulting offspring fluoresce under certain lighting conditions.

16 Evidence This allows the biologist to recognise immediately which individuals have been transformed. This marker has been used in some instances to create fluorescent creatures for aesthetic purposes or even as works of art.

17 Transgenic Cotton—(Bt cotton plants)
Bt cotton is an example of a transgenic organism. In the 1990s, CSIRO scientists in collaboration with the US company Monsanto extensively trialled the use of its Ingard GM cotton, also known as Bt cotton, which is a transgenic species.

18 Transgenic Cotton—(Bt cotton plants)
Over the years, traditional pesticides used on cotton plants had to be made stronger and be applied more frequently to eradicate insect pests such as the caterpillar of the Helicoverpazea moth, a pest which destroys hundreds of millions of dollars worth of cotton each year.

19 Transgenic Cotton—(Bt cotton plants)
With increased sprayings, these caterpillars were building up immunity to the pesticides due to natural selection. Bt cotton plants were genetically modified and contain a gene that codes for the production of a protein that kills the caterpillar of the Helicoverpazea moth.

20 Transgenic Cotton—(Bt cotton plants)
The insertion of the Bt gene into the cotton plant has reduced the need to use pesticides to kill these caterpillars, which is better for the environment and reduces the development of pesticide resistance in the caterpillars. The gene is called Bt because it was originally taken from the soil bacterium, Bacillus thuringiensis.

21 Transgenic Cotton—(Bt cotton plants)
While cotton growers in New South Wales and Queensland would normally spray their crops numerous times in one growing season, they now only spray occasionally to eliminate sucking insects and mites, using a narrow spectrum pesticide that does not wipe out beneficial insects (such as ladybirds and wasps) in the way the powerful, broad spectrum sprays for Helicoverpazea used to.

22 Transgenic Cotton—(Bt cotton plants)
The Bt gene codes for the production of the toxic protein in an inactive form that is harmless to humans and most animals, and even to most insects. However, when the protein is eaten by a caterpillar, it is converted by the digestive system into an active form that kills the insect.

23 Production of Transgenic Cotton
First: Scientists cut normal cotton seedlings into small pieces and place them on a solid growth medium where they grow into calluses. After about six weeks they transfer the callus cells to a liquid medium where they are given hormones to induce them to grow into cotton plant embryos.

24 Production of Transgenic Cotton
Second: By genetic engineering, the Bt gene is extracted from a bacterium, Bacillus thuringiensis, using restriction enzymes.

25 Production of Transgenic Cotton
Third: The Bt gene must then be transferred to the cotton plant embryos. This is done using a second bacterium as a carrier or vector. This bacterium, called Agrobacterium tumefaciens, is known to cause the disease crown gall in plants. This vector is able to inject genes into other cells.

26 Production of Transgenic Cotton
The cotton plant embryos are dipped in a solution that contains a mixture of the vector, Agrobacterium, and the extracted Bt genes (which have recombined with the Agrobacterium genome), and the vector bacteria inject the Bt genes into the cotton cells.

27 Production of Transgenic Cotton
Fourth: Once the gene is inserted, the embryos containing the Bt genes are grown in tissue culture and are then placed on another solid medium and germinated into small plants, which are planted in pots and grown in glasshouses. These plants are now a transgenic species, containing a gene from another species in their genome.

28 Production of Transgenic Cotton
Cotton is a very difficult plant to culture, but CSIRO scientists have developed workable techniques for growing three varieties of cotton. In order to increase the success of the project, the scientists have developed four different insecticidal genes to use in the cotton. However, the project has been very controversial, with critics claiming that it is doing more harm than good.

29 Reducing the Risk of Resistance
Ingard, a cotton containing the product of a single gene, has been replaced by Bollgard II cotton, which contains two inserted genes and produces two lethal proteins against the caterpillar. It is highly unlikely that the caterpillar will become resistant to both genes.

30 Reducing the Risk of Resistance
In addition, cotton farmers plant a ‘refuge crop’ of pea plants in a field nearby, so that moths that may have one recessive allele for resistance to Bollgard II continue to interbreed with moths who feed on the ‘refuge crop’, to reduce the chances of in- breeding caterpillars with double recessive alleles, which could confer resistance.

31 Activity/Homework -Watch Bill Nye Video a

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