Genetic Engineering Flashcards
What do you call an organism who has a gene from another organism
Transgenic
How do we isolate the desired gene
The most common technique is using enzymes called restriction endonucleases to cut the required gene from the DNA of the organism. After breaking the strand at specific parts of the base sequence, it leaves the ends as unpaired and exposed, called sticky ends. They make it easier to insert the desired gene into the DNA of a different organism
What is another way of isolating genes
It involves isolating thr mRNA for the desired gene and using the enzyme reverse transcriptase to produce a single strand of complementary DNA. This makes it easier to identify the desired gene, as a particular cell will make some very specific types of mRNA. For example B cells of the pancreas make insulin and produce a lot of insulin mRNA molecules
What happens with the dna we have isolated
It must be inserted into a vector in order to carry it to the host cell
What are the most commonly used vectors
Bacterial plasmids - circular molecules of DNA that is separate from the chromosomal dna that can replicate independently. Once a plasmid gets into a new host cell it becomes a part of the host DNA and it is now recombinant DNA.
What else must plasmids have to be vectors
They also must have a marker gene for something like antibiotic resistance. Because this enables scientists to determine if the bacteria have taken up the plasmid, by growing them in a medium containing antibiotics, meaning they’ve successfully taken on the gene
How do we insert a DNA fragment into a plasmid?
The same restriction endonucleases that isolated the DNA fragment must be used to cut the plasmid. This results in the plasmid having complimentary sticky ends with the DNA fragments. And once the sticky ends have lined up, the enzyme DNA ligase forms phosphodiester binds between the sugar and the phosphate groups on the two strands of DNA, joining them together.
How do we transfer this new plasmid into the host cell
Through a process called transformation. Place the host cell and the plasmid in a calcium rich medium and increase the temperature. This causes the bacterial membranes to be permeable and the plasmids can enter
Another method of transportation is electroportation where a small electric current is applied to the bacteria. This makes the membranes very porous and so the plasmids can move in. However current has ti be carefully controlled or it could destroy the whole cell.
What is electrofusion
It’s another way of producing GM cells - tiny electric currently are applied to the membranes of two different cells. This fuses the cell and nuclear membranes I’d the two different cells together forming a hybrid polyploid cell, containing DNA from both. It can be used to produce GM plants.
However it doesn’t work as effectively in animals as it does plants.
What is genetic engineering in prokaryotes used for
Bacteria and other prokaryotes have been genetically modified to produce many beneficial substances for us humans. This includes insulin, human growth hormone, clotting factors, antibiotics, vaccines, enzymes…
Use of genetic engineering in plants
The use of bacteria A. Tumefaciens causes tumours in healthy plants.
A desired gene such as for drought resistance or pesticide production;will be placed in the Ti plasmid of A. Tumefaciens along with a marker gene. This is then carried directly into the plant cell dna and the transgenic plant cells form a callus, which is a mass of GM a plant cells, each of which can be grown into a new transgenic plant.
Engineering in animals
Much harder as it’s harder to manipulate the animal cell membranes than plant
What concerns are the there for genetically modified soya
One genetically modified soya plant has been made to produce the Bt protein. This protein is toxic to many of the pest insects that attack the plant and is widely used as a pesticide by farmers.
This reduces the amount of pesticide spraying which can harm the environment. Resistant crops can be produced, increasing yield. It can also reduce competition, however this may encourage a mono culture, and decrease genetic diversity. Genes could also spread to wild causing super weeds
What is pharming
The use of genetically modified animals to produce pharmaceuticals
What are two ways of pharming
Creating animal models - animals are genetically engineered to have diseases so that we can use them as models to develop new therapies or medicines.
Creating human proteins - hereditary anti thrombin deficiency makes blood clots more likely, but can be reduced with anti thrombin. DNA fragments that code for anti thrombin are injected into goat embryo. This embryo gets implanted into a female goat and when the offspring is born, it is tested to see if it produces anti thrombin. If it does, selective breeding is used to produce a herd of anti thrombin goats. This Protein is then extracted and used to make a drug that can be given,
Ethical issues with pharming
Positives - this drug can be made in large quantities compared to other methods of production
However this method could have harmful side effects on the animal and doing this way reinforces the idea that animals are ‘assets and treated however we choose’.
What are problems of patenting
People in LEDCs may be prevented from using GM crops due to patents. People who invented a certain GM crop or technique may patent it so someone else cannot use those crops or methods without buying it from the people who own the patent. People who actually need these crops and techniques may not be able to afford, such as those crops of insect resistance… . An example is a company that developed herbicide resistant and pesticide producing soya have patented this to only farmers can buy from them.
What are some companies doing to help patenting
The international rice research institute works to develop engineered rice to specifically support farmers in LEDCs. They have genetically engineered flood resistant ‘scuba rice’ which gives 70-80% max yield after flooding for up to 3 weeks
What is gene therapy
Some human diseases arise due to faulty genes. Gene therapy aims to replace these ones with healthy ones,
What is somatic cell gene therapy compared to germ line gene therapy
Somatic cell gene therapy is Replacing mutant allele with a healthy allele in the affected somatic cells.
Been line cell gene therapy aims to put a healthy allele into the Germ cells, usually the eggs, or an embryo immediately after fertilisation. The individual would be born healthy with a normal allele In place and would pass it onto the offspring
Genetically engineering pathogens
Scientists have found that some tumour cells have receptors on their membranes for the poliovirus - so the poliovirus wiki recognise and attacks them.
By GM these poliovirus to inactivate the genes that cause poliomyelitis, scientists can use it to attack and kill cancer cells without causing disease. This may lead to a treatment for cancer
Ethics of using pathogens
Previously untreatable things are now treatable.
However scientists researching the pathogen could be infected and mass outbreak starts
In the body it could revert and cause outbreak
In the wrong hands could be used for biowarfare
What is recombinant DNA
DNA combined from two sources
