6 Genetic modification Flashcards
What is a gene?
It is a section of a molecule of DNA that
codes for the production of a protein.
What does the coding strand of the DNA contain?
It contains triplets of bases.
What does each triplet code for?
Each triplet coding for one amino acid.
Why do different genes produce different proteins?
Different genes produce different proteins because each has a unique sequence of bases that codes for a unique sequence of amino acids.
What is an image that shows the role of DNA in protein synthesis?
What are examples for what the proteins that are produced can be?
- An enzyme that controls a particular reaction inside a cell or in the digestive
system. - A structural protein like keratin in hair, collagen in skin or one of the many
proteins found in the membranes of cells. - A protein hormone such as insulin.
- A protein with a specific function such as haemoglobin or an antibody.
What is the basis of genetic engineering?
The production of recombinant DNA.
What is recombinant DNA?
DNA made by genetic engineering,
by combining DNA from two species of organisms.
How is DNA combined from two species of organisms?
A section of DNA – a gene – is cut out of the DNA of one species and inserted into the DNA of another.
Why is this DNA called recombinant?
This is because the DNA from two different organisms has been ‘recombined’.
What is the organism that receives the gene from a different species called?
A transgenic organism.
What is a transgenic organism?
An organism that has been engineered with a gene from another species.
What happens to the organism receiving the new gene?
The organism receiving the new gene now has an added capability.
Why will it have an added capability?
It will manufacture the protein that the new gene codes for.
What is an example of the new organism manufacturing the protein that the new gene coded for?
A bacterium receiving the human gene that codes for insulin production will
make human insulin.
What happens if these transgenic bacteria are cultured by the billion in a fermenter?
They become a factory for making human insulin.
when did the breakthrough in being able to transfer DNA from cell to cell come about?
When it was found that bacteria have two sorts of DNA.
What are the two types of DNA that bacteria have?
The DNA found in their bacterial ‘chromosome’ and much smaller circular pieces of DNA called plasmids.
What is a plasmid?
It is a small circular piece of DNA found in bacteria and used in genetic engineering.
What do bacteria naturally do in terms of plasmids?
Bacteria naturally ‘swap’ plasmids.
What did biologists find out in terms of these plasmids?
Biologists found ways of transferring
plasmids from one bacterium to another.
What were biologists missing?
The next stage was to find molecular
‘scissors’ and a molecular ‘glue’ that could cut out genes from one molecule
of DNA and stick them back into another.
What are the molecular ‘scissors’ in question?
Restriction endonucleases/enzymes.
What are these restriction endonucleases/enzymes?
It is an enzyme used in genetic engineering to cut out a section from a molecule of DNA.
What are these restriction endonucleases/enzymes used for?
They are enzymes that cut DNA molecules at specific points. Different restriction enzymes cut DNA at different places. They can be used to cut out specific genes from a molecule of DNA.
What are ligases?
They are enzymes used to join pieces of DNA in genetic engineering.
What are ligases used for?
(or DNA ligases) are enzymes that join the cut ends of DNA molecules.
What does each restriction enzyme recognise?
Each restriction enzyme recognises a certain base sequence in a DNA strand.
What happens whenever restriction enzymes recognise a certain base sequence?
Wherever it encounters that sequence, it will cut the DNA molecule.
What can we suppose?
Suppose a restriction enzyme recognises the base sequence G-A-A-T-T-C.
How will the restriction enzyme then cut this sequence?
It will only cut the DNA molecule if it can ‘see’ the base sequence on both strands.
What are two ways in which restriction enzymes can cut DNA?
- Straight cuts.
- Staggered cuts.
What do restriction enzymes that make straight cuts produce?
Some restriction enzymes make a straight cut and the fragments of DNA
they produce are said to have ‘blunt ends’.
What do other restriction enzymes that make staggered cuts produce?
These produce fragments of DNA with
overlapping ends with complementary bases.
What are these overlapping ends called?
‘Sticky ends’.
Why are they called sticky ends?
This is because fragments of DNA with exposed bases are more easily joined by ligase enzymes.
What is a diagram which shows how restriction enzymes cut DNA to form blunt ends?
What is a diagram which shows how restriction enzymes cut DNA to form sticky ends?
What did this process allow biologists to do?
Biologists now had a method of transferring a gene from any cell into a
bacterium.
What could they now do in terms of plasmids and bacterium?
They could insert the gene into a plasmid and then transfer the plasmid into a bacterium.
What is this plasmid called?
A vector.
What is a vector?
Structure which can be used to transfer genes in genetic engineering, e.g. a plasmid.
What is a diagram which shows the stages in producing transgenic bacterium?
What is another vector that has been used to introduce foreign DNA into bacterial cell?
The bacteriophage.
What is the bacteriophage?
It is a virus that infects bacteria. Used as a vector in genetic engineering.
What kind of virus is a bacteriophage?
It is a virus that attacks a bacterium.
How does the bacteriophage attack a bacterium?
It does this by attaching to the cell wall of the bacterium and injecting its own DNA into the bacterial cell.
What happens to the DNA of the host cell?
This DNA becomes incorporated into the DNA of the host cell.
What does this incorporation cause?
It eventually causes the production of many virus particles.
What happens if a foreign gene can be inserted into the DNA. of the virus?
The virus will inject it into the bacterium along with its own genes.
What is now most commonly used as a vector?
Viruses were used as vectors in the early days of genetic modification, but most gene transfer is now carried out using plasmids.
What is an image that shows a bacteriophage attacking a bacterial cell?
How have different bacteria been genetically modified?
Different bacteria have been genetically modified to manufacture a range
of products.
What happens once they have been genetically modified?
Once they have been genetically modified, they are cultured in fermenters to produce large amounts of the product
What are some examples of the genetically modified bacteria producing large amounts of a product?
- Human insulin.
- Enzymes for washing powders.
- Enzymes in the food industry.
- Human growth hormone.
- Bovine somatotrophin.
- Human vaccines.
How is human insulin used?
People suffering from diabetes need a reliable source of insulin. Before the use of genetic engineering to make human insulin, the only insulin available was extracted from the pancreases of other animals such as cattle. This is not quite the same as human insulin and does not give the same level of control of blood glucose levels.
How are enzymes for washing powders used?
Many stains on clothing are biological.
Blood stains are largely proteins, grease marks are largely lipids. Enzymes can digest these large, insoluble molecules into smaller, soluble ones. These then dissolve in the water. Amylases digest starch, proteases digest proteins and lipases digest lipids. Bacteria have been genetically engineered to produce enzymes that work at higher temperatures, allowing even faster and more effective action.
How are enzymes in the food industry used?
One bacterial enzyme used in the food
industry is glucose isomerase. This enzyme catalyses a reaction which
converts glucose into a similar sugar called fructose. Fructose is much
sweeter than glucose and so less is needed to sweeten foods. This has two
advantages – it saves money (since less is used) and it means that the food
contains less sugar and is healthier.
How is the human growth hormone used?
The pituitary gland of some children does not produce enough of this hormone and they show a slow rate of growth. Injections of growth hormone from genetically modified bacteria restore normal growth patterns.
How is bovine somatotrophin used?
(BST) (a growth hormone in cattle) This hormone increases the milk yield of cows and increases the muscle (meat)
production of bulls. Giving injections of BST to dairy cattle can increase the milk yield by up to 10 kg per day. To do this they need more food, but this increased cost is more than offset by the increased income from the
increased milk yield.
What is an image which shows the effect of bovine somatotrophin on milk yield?
How are human vaccines used?
Bacteria have been genetically modified to produce the antigens of the hepatitis B virus. This is used in the vaccine against hepatitis B. The body makes antibodies against the antigens but there is no risk of contracting the actual disease from the vaccination.
What has happened since the basic techniques of transferring genes were developed?
Many unicellular organisms have been genetically modified to produce useful
products.
What have these basic techniques allowed us to do?
Techniques for transferring genes into plants and animals have also been developed.
Why does this technique work for bacteria?
In the case of bacteria, this is fine – a bacterium only has one cell.
Why doesn’t this technique work for plants?
But plants have billions of cells and to genetically modify a plant, each cell
must receive the new gene.
What are the two main stages of any procedure for genetically modifying plants?
- Introducing the new gene or genes into plant cells.
- Producing whole plants from just a few cells.
How did biologists struggle in terms of genetically modifying plants?
Biologists initially had problems in inserting genes into plant cells.
What did biologists then discover?
They then discovered a soil bacterium called Agrobacterium, which regularly inserts plasmids into plant cells.
What is agrobacterium?
A vector.
What happens now that a vector has been found?
The rest became possible.
What is a diagram which shows how you can genetically modify plants using agrobacterium?
Can this technique be used on all plants?
No, this technique cannot be used on all plants.
What do we do for other plants then?
Agrobacterium will not infect cereals and so another technique was needed for these.
What is the other technique used for genetic modification in plants?
The ‘gene gun’ was invented.
What is this ‘gene gun’?
This is, quite literally, a gun that fires a golden bullet.
What is this golden bullet?
Tiny pellets of gold are coated with DNA that contains the desired gene
What then happens to these tiny pellets of gold?
These are then ‘fired’ directly into plant tissue.
What has research shown if the tissue is young and delicate?
Research has shown that if young, delicate tissue is used, there is a good uptake of the DNA.
What can then be done with this genetically modified tissue?
Research has shown that if young, delicate tissue is used, there is a good uptake of the DNA.
What has the gene gun made possible?
The gene gun has made it possible to genetically modify many cereal plants as well as tobacco, carrot, soybean, apple, oilseed rape, cotton and many others.
What are available to plant growers and farmers already?
Large numbers of genetically modified plants.
How have some fruits and vegetables been engineered?
To have extended shelf lives.
What does an extended shelf life mean?
That they last longer before they start to go bad.
How have other crop plants been modified?
To be resistant to herbicides (weedkillers).
Why is this resistance good?
This allows farmers to spray herbicides at times when they will have maximum effect on the weeds, without affecting the crop plant.
What is a disadvantage, or safety concern about this resistance?
There are concerns that this will encourage farmers to be less careful in their use of herbicides
What has the gene gun allowed biologists to do?
The gene gun allowed biologists to produce genetically modified rice called
‘golden rice’.
What is golden rice?
This rice has three genes added to its normal DNA content. Two of these come from daffodils and one from a bacterium.
What do these three genes do?
Together, these genes allow the rice to make beta-carotene – the chemical
that gives carrots their colour. It also colours the rice, hence the name ‘golden rice’.
Why is this beta-carotene useful?
The beta-carotene is converted to vitamin A when eaten. This could save the eyesight of millions of children in less economically developed countries, who go blind because they do not have enough vitamin A in their diet.
What else are genetically modified plants allowing humans to do?
They allow humans to resist infection.
What is an example of this genetic modification concerning resisting infection?
Biologists have succeeded in modifying tobacco plants and soybeans to
produce antibodies against a range of infectious diseases
What is a risk associated with a vaccine containing viruses?
There is always a risk with a vaccine containing viruses that they may somehow become infectious again.
How have we overcome this risk?
This could not happen with a vaccine containing only plant-produced antigens.
What are some examples that research into the genetic modification of plants hopes to provide plants with?
- Increased resistance to a range of pests and pathogens.
- Increased heat and drought tolerance.
- Increased salt tolerance.
- A better balance of proteins, carbohydrates, lipids, vitamins and minerals.
What would happen if biologists could modify crop plants like cereals and potatoes to allow nodules of nitrogen-fixing bacteria to form on their roots?
If they could, vast areas of infertile soil would be able to yield good crops of cereals without the need to use large quantities of fertilisers.
What would the bacteria in the root nodules do?
They would obtain nitrogen from the air in the soil and ‘fix’ it in a more usable form (usually ammonia).
What would making it into ammonia do?
By doing this, they would
make a supply of usable nitrogen available to the plants.
What would the plants do with this nitrogen?
The plants would convert this into plant protein and use the protein for growth. The cost of producing these crops would decrease dramatically.
What are animals, like plants?
Are multicellular.
What do animals being multicellular mean in terms of genetic modification?
It is not enough simply to transfer a gene to a cell.
Why is it not enough?
That cell must then grow into a whole organism.
What does the plasmid technology used to create genetically modified plants depend on?
The modified cells being grown into
whole plants using micropropagation.
Does this micropropagation exist for animals?
No.
What are the most successful techniques of genetically modifying animals?
The most successful involves injecting DNA directly into a newly fertilised egg cell. This develops into an embryo, then an adult.
What benefits can research of this kind produce?
- Manufacture of human proteins, such as antibodies, blood clotting factors
or alpha-1-antitrypsin (AAT). - Increased production of a particular product, e.g. higher milk yield in cows,
greater muscle mass in animals used for meat. - Increased resistance to disease.
- Production of organs for transplantation (xenotransplantation).
What is a diagram showing the procedures used in producing genetically modified animals?
