Genetic engineering Flashcards
What are genetically modified organisms
Organisms that have had their genomes altered by genetic engineering techniques
Why do scientists develop GMO’s
These organisms have a more desirable phenotype
What is a transgenic organism
A genetically modified organism that contains recombinant DNA
What is the DNA from another organism that is put in the GMO called
Recombinant DNA
What was the first type of organism that was genetically modified and why
Bacteria which was engineered to produce the human protein insulin
What is the first step required to create GM bacteria
isolate the desired gene which encodes insulin from the genome of an organism (human)
How can the desired gene be isolated
Restriction endonuclease enzymes can cut the gene out of the chromosome
What are Restriction endonuclease enzymes
A type of enzyme that can cut up DNA at a specific sequence of bases called recognition sites
What are recognition sites
Sequences of bases specific to each restriction enzyme that are usually palindromic
What are the 2 types of cuts restriction endonuclease enzymes can make
- Clean straight cuts through both strands of DNA at the recognition site - Cut the 2 DNA strands unevenly, creating sticky ends
What are sticky ends
Short regions at the end of DNA that are single stranded and therefor have exposed unpaired nucleotides
In order to transfer the isolated gene into the bacteria what must first be done
The gene must be inserted into a plasmid
What is a plasmid
A circular length of DNA that is found inside bacteria and able to pass into them
How is the plasmid cut
Using the same restriction endonuclease enzymes used to isolate the gene
What does using the same restriction endonuclease enzymes ensure
Ensures that the sticky ends of the desired gene and the plasmid are complementary and can therefor anneal to each other
What happens once the plasmid and the desired gene have annealed
The DNA of the gene and the plasmid permanently joins together by the enzyme DNA ligase
What does this create when ligase has worked
Recombinant plasmid
What is done with the recombinant plasmid
It is transferred into the host bacterial cell in a process called transformation.
What can occur once the bacteria has been ‘transformed’
It will be able to produce the protein
What is the issue with transformation
It is an inefficient process and only around 1% of bacteria successfully take up the plasmid
What is the issue with some bacteria taking up the plasmid but not others
Bacteria that don’t take it up are not useful so must be removed
How are bacteria that have taken up the plasmid identified
The plasmids contain a marker gene which makes it resistant against an antibiotic. All are then cultured on a petri dish in a medium that contains an antibiotic which kills the bacteria that were not transformed
What will happen to the transformed bacteria that survive the petri dish
They will grow colonies which are then cultured in a fermenter. The protein produced by the bacteria is then extracted from the culture and purified
What does the plasmid act as
A vector
What is the benefits of using human insulin produced by bacteria over insulin taken from animals
- Human insulin has a lower risk of being rejected from the immune system and lowers the risk of infection - Human insulin is less expensive to obtain than pig insulin which lowers the price of the treatment
What is the negatives of using human insulin produced by bacteria over insulin taken from animals
- Many people have ethical concerns about the introduction of human DNA into bacteria - Marker genes for antibiotic resistance may be transferred from GM bacteria to other pathogens as bacteria can transfer plasmids - The ability to genetically modify bacteria could result in the production of more lethal pathogens which could be used in biological warfare
What is a way of getting around the issue of antibiotic resistance may be transferred from GM bacteria to other pathogens
They modify GM bacteria so that they are unable to produce an essential nutrient or amino acid and therefor dependant on its presence in the culture medium. This also means GM bacteria cannot survive outside the lab and reducing the chance of them coming into contact with pathogens.
How can plants be genetically modified
- Agrobacterium. Tumefaciens - A gene gun - Electrofusion
What does Agrobacterium. Tumefaciens do?
It is a bacteria that infects plants and inserts a Ti plasmid which causes the plant to form tumours
How are GM plants made with Agrobacterium. Tumefaciens
The desired gene is inserted into the Ti plasmid along with a marker gene (for antibiotic resistance)
What does the Ti plasmid become when it has had the desired gene inserted into it
A recombinant Ti plasmid
What is done with the recombinant Ti plasmid
It is inserted into the Agrobacterium. Tumefaciens
What does the Agrobacterium. Tumefaciens do
Infects the plant and inserts the desired gene and the marker gene into the plant genome. This causes a genetically modified mass of cells to form called a callus
What do scientists do with the callus
Ensure it has been successfully genetically modified by growing the callus on a medium containing antibiotics
What can then be done with the callus when it has been tested for its genetic modification
The callus can be used to produce many GM plant clones by growing pieces of the callus in a medium containing plant hormones. Each piece of callus will develop leaves and shoots from tiny plants called plantlets
What is done with the plantlets
They are potted in soil and will eventually develop into a fully grown GM plant
How can plants be modified without the direct use of vectors
Gene guns
What does a gene gun do
It shoots small pieces of gold or tungsten into plant cells
What are the small pieces of gold or tungsten coated with
The DNA sequence of the desired gene and a marker
How is use of gene gun ineffective
Not all plant cells will survive the use of a gene gun or incorporate the DNA into their genomes
What is done with the plant cells after the gene gun has been used on them
They are cultured in a medium containing antibiotics and plant hormones and the GM plant cells grow to form a callus
What is the callus used to form
Many GM plant clones
What is plant Pharming
Where GM plants are developed to produce a specific drug or medical protein
Where can the drug or medical protein be produced in the plant
In specific parts such as seeds, leaves or tubers
What is done with the plant organs of the GM plant once it is fully grown
They are harvested and the drug or medicinal protein is then extracted
What are the uses of plant PHarming
- Can be used as a method of combatting infectious diseases caused by pathogens - They can be used to produce antibodies that are specific to antigens found on a pathogen - They can produce the antigens of specific pathogens which can then be used to develop a vaccine against a specific disease
What is the main staple diet for the majority of humans
Plants
What is the issue with plants being the main staple diet for the majority of humans
They are vulnerable to disease, pests and adverse environmental conditions such as floods or drought
What do crops face competition with
Weeds, for resources, which grow faster and may outcompete them
What do the issues to do with crops cause
They reduce the yield and cause farmers financial issues. This may mean that we cant feed the overpopulated planet
What is the issue with selective breeding to produce crops with more desirable traits
It is a very slow ‘hit or miss’ technique
What are the advantages of genetically modifying plants
They can be modified to have specific desirable traits
What types of genes can be introduced to boost crop yield
- Herbicide resistance - Pest resistance - Disease resistance - Drought or flood resistance - Increased nutritional value - Extended shelf life
What are the risks of GM crops
- They contain marker genes for antibiotic resistance - Genes that provide plants with resistance to disease and herbicides may spread onto wild plants - Pests or pathogens could evolve resistance to the pesticide in GM crops - GM crops with resistance to floods or drought may be able to grow in countries that previously did not have a suitable climate - Issues with patenting
What is the issue with GM plants containing marker genes for antibiotic resistance
These genes could possibly be transferred to pathogens in the intestine of the consumer
What is the issue with Genes that provide plants with resistance to disease and herbicides may spread onto wild plants
Could causes issues such as super weeds
How could the risk of Pests or pathogens evolving resistance to the pesticide in GM crops be reduced
By producing GM crops that produce multiple pesticides
What are the issues with patenting GM crops
Patents prevent farmers from being able to grow the crops without paying for the seeds. GM crop seeds may be more expensive so the farmers who need them most may not be able to afford them. They may make seeds infertile so farmers cant use seeds from the harvest for growing again and have to buy more
What are the methods of genetically engineering animals
- Transfection - Liposomes - Microinjection
Describe transfection
Viruses can be used as vectors to insert DNA into animal cells in a process known as transfection
What cell has to be used for transfection and why
A fertilised egg cell (zygote) so that the whole animal becomes GM
What must first be done in transfection
The desired gene must first be incorporated into the genome of a virus. and the viral genome must be modified so that the virus can enter but not replicate inside host cells
Which viruses are used in transfection
Retrovirus or adenovirus
What is the benefit of viral genome being modified so that the virus can enter but not replicate inside host cells
It reduces the risk of viral vectors causing disease by damaging the host cells
What does the virus do once it has entered the cell
It incorporates its DNA, including the desired gene into the animal genome
What is a liposome
A small sphere formed from a phospholipid bilayer
How do liposomes GM animals
Many copies of the desired gene is wrapped in the liposomes which are easily able to fuse with animal cell membranes, this results in the delivery of the desired gene into the cytoplasm of the host cell
What is the difficulty with liposomes
The DNA then needs to be incorporated into the animal genome which is a challenging and inefficient process
Describe a microinjection
It is the process of inserting DNA directly into the nucleus of an animal cell using a very fine micropipette
What piece of equipment does a microinjection need and what does it do
Needs a micro manipulator which does the microinjection with greater precision than can be achieved manually
What is the issue with microinjections
It is very inefficient as many cells must be injected before one successfully incorporates the DNA into the host genome
What are GM animals most commonly used for
PHarming
Why may animals be GM instead of bacteria for PHarming
Animals may be better at producing larger more complex eukaryotic proteins
Why are mammals most commonly used in PHarming
They can secrete the medically required human proteins in milk
Describe the process of GM an animals to produce a specific protein
- Desired gene is introduced into a fertilised female egg cell - The gene contains a tissue specific promoter sequence so that the gene is only expressed in the mammary glands - So when the GM female mammal reaches maturity and gives birth it will start producing milk that contains the human protein which can then be extracted and used for medical applications
What can GM animals also be used for
Models in scientific research
How do GM animals act as models
They can be GM so that some of their genes are silenced in order to model human diseases caused by faulty genes
What is it called when a gene is silenced by genetic engineering
Gene knockout and the animal is called a knockout animal
What are knockout mice used for and how
Used as models for cancer by deleting genes involved in regulating cell division. Then these can then be used to test possible cancer treatments
What are some ethical issues with GM animals
- Some people may have an ethical issue with the insertion of human genes into animals - Most GM animals die during development as the insertion of a gene can interrupt essential functioning of other genes - GM animals that do survive may have harmful side effects like lameness and susceptibility to stress - Using animals as models of human diseases will negatively effect their welfare
