GCSE biology notes: Genetic engineering - applications of GM products

Genetic Engineering - techniques - splicing genes with enzymes!

uses e.g. making insulin, GM crops, medical applications

examples of biotechnology

Doc Brown's Biology Revision Notes

Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent

 This page will help you answer questions such as ...

 What do we mean by genetic engineering?

 Describe the basic principles of how to transfer a gene from one organism's genome to the genome of another organism.

 Can you describe some uses of genetic engineering?

 Be able to discuss the 'pros and cons' of genetic engineering.

Note: GM is used as an abbreviation for genetically modified products i.e. the produce of genetic engineering.



Introduction to genetic engineering

The basic idea of genetic engineering is to transfer a gene that gives rise to a desirable characteristic (trait) from one organism's genome to a different organism's genome, so that it acquires that desired characteristic.

  • Know and understand in genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms.

  • Be able to demonstrate an understanding of the process of genetic engineering, including the removal of a gene from the DNA of one organism and the insertion of that gene into the DNA of another organism
    • This is exemplified by the production of insulin from bacteria by inserting the human insulin gene into bacteria and growing the bacteria to produce lots of insulin quickly and economically efficiently.
    • This amounts to changing the characteristics of an organism by changing its genes.

    • Useful genes from organism A can be inserted into organism B.

    • The desired useful gene (carrying desired characteristic) is cut out and isolated from the source organism A's chromosome by specific enzymes and inserted into a vector.

      • Restriction enzymes recognise specific sequences of DNA and cut the DNA at these points.

      • DNA ligase enzymes are employed to join the two pieces of DNA together at their 'reactive' ends.

      • The two different bits of DNA joined together are known as recombinant DNA.

      • A vector is something used to transfer DNA into the target cell e.g. a plasmid can be used to transfer DNA into a bacteria.

        • A plasmid is a relatively small ring of DNA.

      • The vector is usually a virus or a bacterial plasmid - a circular piece of DNA found in bacterial cells.

      • Plasmids are small circular molecular sections of DNA which can be transferred between bacteria.

      • When the vector is introduced to the target organism, the useful genes inserted into the cell.

    • Other enzymes are then used to remove an 'undesired' gene from organism B, the one you want to modify.

    • Then, via other enzymes, the desired transplanted gene can be inserted into organism B.

    • It is hoped one day to cure the genetic disorder cystic fibrosis with gene therapy ie replacing faulty genes with correctly functioning genes.


The production of insulin - as an example of the medical use of genetic engineering in biotechnology

  • The principles of genetic engineering are illustrated by the production of insulin from bacteria (shown below).

    • Genetic engineering is essentially the process of transferring a useful gene from one organism to another.

    • In this case, bacteria are genetically engineered to make human insulin.

  • 1. An appropriate host bacteria is selected that will give a good yield of insulin (or any other desired product).
  • 2. The bacterial plasmids are extracted from the bacteria - the plasmid acts as the vector for the insulin gene.
  • 3. The vector plasmid DNA is cut by the restriction enzymes - these enzymes recognise specific sequences of DNA and cut the DNA at these points.
  • 4. The human gene responsible for insulin production (or other gene coding for something else) is cut from the human chromosomal DNA with the same restriction enzymes.
  • 5. From the two splits, you get reactive sites on the ends (described as 'sticky') which are short tails of unpaired bases that are complimentary to each other.
    • Enzymes (ligases) are then added and used to insert ('splice') the insulin (or other desired) gene into the bacterial plasmid DNA, forming the recombinant DNA.
    • The DNA ligase enzymes 'glue' the 'sticky' reactive ends together.
  • 6. The modified plasmid vectors containing the new DNA are inserted into the host bacteria cells.
  • 7. The bacteria rapidly reproduce when grown in a fermenter under highly controlled conditions - in doing so they use the inserted gene to make the protein you want e.g. the protein hormone molecule insulin.
    • So the host cells are using the inserted gene to produce the desired product e.g. insulin.
  • 8. The insulin (or other product) can be produced in bulk and extracted-harvested and purified and the waste bacterial cells destroyed.

BUT, still one more complication!

Unfortunately, not all the host cells will have been modified correctly e.g. a faulty vector transfer.

Therefore in the final stage, you have to be able to select and identify the individual host cells that have successfully incorporated the desired gene.

Antibiotic resistance gene markers are used to identify the correctly modified host cells.

A marker gene coding for antibiotic resistance is inserted into the vector plasmid at the same time as the gene for the desired characteristic.

The host bacteria are grown in a special vessel containing antibiotics.

Only the bacteria containing the marker gene will be able to survive and reproduce, because the antibiotics will kill the rest of the cells that were not genetically modified correctly.

Working two genes in tandem! Clever stuff!


Examples of genetically modifying a plants genome for an enhanced characteristic

As we have seen, plants can be genetically modified to enhance desired characteristics.

GM technology allows the transfer of useful genes into plants, so they develop useful enhanced characteristics e.g. anti-pest or increased size of grain.

GM crops are controversial.

The examples below describe techniques used in agriculture to produce crops with desirable characteristics that increase crop yields.

Example 1

Scientists frequently used a bacterium call Agrobacterium fumefaciens to genetically modify plants.

The Agrobacterium fumefaciens bacterium invades plant cells and can insert its genes into the plant's genome (DNA) e.g.

A gene is taken from the cells of a herbicide resistant plant and inserted into a plasmid extracted from the Agrobacterium fumefaciens bacteria.

The genetically modified plasmid is inserted back into the bacterium.

The bacterium, with the newly inserted gene, can then enter the target plant cells and genetically modifies the plant cell's genome.

You quite simply let the modified bacterium infect the plant cells, modifying their DNA.

The modified plant cells can then be used to grow mature plants with their newly acquired gene giving them the anti-herbicide characteristic.

 

Example 2

A bacterium called Bacillus thuringiensis produces a toxin (a protein) that is poisonous to insect larvae that feed on plant roots and the adults on the leaves, damaging the crops.

The gene in the bacterium that codes for the toxin is inserted into the genome of crops such as corn and cotton.

The crops produce the toxin protein in their stems and leaves giving the plants insect-resistance.

The toxic protein is specific to insect pests (important) and harmless towards to animals, including humans and other harmless insects - but the long-term effects of the genetically modified genome are unknown.

This method, in principle, is good for farming because it reduces the use of insecticides, using less insecticides is less damaging to ecosystems in the countryside.

As the insects feed on the crops they are constantly exposed to the toxin, so that later generations of the susceptible insects may develop resistance to the toxin and no longer die from its effects.

Farmers can use other insecticides - but these are already being overused - one of the main reasons for the decline of bee populations in many countries.

(When writing this, I found from the internet, that toxin-resistant strains of insects are already evolving!).

 

Other examples in brief

3.  Gene that helps fish survive in cold water has been inserted into the genome of a tomato plant to help the plant survive in a colder climate i.e. the plant is able to cope with lower temperatures than the original plant.


More on examples of the use of genetic engineering

Be able to discuss an understanding of the advantages and disadvantages of genetic engineering to produce GM organisms, including:

  • a) Increase the content of beta-carotene in golden rice to reduce vitamin A deficiency in humans.
    • Beta-carotene is essential for our bodies to make vitamin A.
      • Without beta-carotene in our diet, we can't make vitamin A.
        • Vitamin A is a fat-soluble vitamin that is naturally present in many foods.
        • Vitamin A is important for normal vision, the immune system, and reproduction.
        • Vitamin A also helps the heart, lungs, kidneys, and other organs work properly.
    • Vitamin A deficiency is common in many Asian and African countries and can cause blindness.
    • This is due to too little beta-carotene or vitamin A in their diet e.g. there is too little in their traditional rice crops, so in these areas there is a problem of Vitamin A deficiency..
    • Golden rice is a GM rice whose genetic make-up contains two genes from other organisms which enable this variety of rice to produce sufficient quantities of beta-carotene.
      • The gene controlling beta-carotene production was obtained from carrot plants and inserted into the genome of rice plants.
    • With golden rice as part of their diet, the risk of vitamin A deficiency is reduced and less people are likely to go blind.
  • b) The production of human insulin by genetically modified bacteria (discussed in detail above).
    • GM produced insulin production has been described in detail above.
    • The process overall is one of inserting the human insulin gene into bacteria and growing the bacteria to produce lots of insulin quickly and economically efficiently (cheaply!).
    • The resulting, and efficiently produced, insulin can be used to treat people with diabetes, and is an example of genetically engineering bacteria, in this case to produce human insulin.
  • c) In other medical applications, scientists have transferred human genes into cows and sheep to produce useful proteins.
    • You can 'manufacture' human antibodies used in the treatment of arthritis, multiple sclerosis and some types of cancer.
    • These useful proteins can be extracted from the 'host' animal e.g. from cows milk.
    • It might be possible in future to use animal organs grown specially for transplant operations - ethical issues!
  • d) The production of insect-resistant and herbicide-resistant crop plants
    • Crops can be genetically engineered to grow and survive in drought conditions - lack of water puts a big constraint on the quality and quantity of crop yields.
    • You can modify the genetic make-up of plants by inserting genes that resistant to certain 'pests' e.g. fungal attack or insects.
    • You can also make crops resistant to a herbicide being used to kill all weeds in the field of growing crops i.e. only the crop that you want survives!
    • All of these effects will help to increase the quality and yield of crop yield.
    • For more details see Examples of genetically modifying plants for an enhanced characteristic
       
  • e) Medical researchers are trying to develop genetic modification treatments for inherited diseases caused by faulty genes.
    • The idea is to insert correctly working genes into people suffering from the disorder caused by faulty genes.
    • This technique is called gene therapy.
    • It is sometimes possible to transfer the 'working' gene when the organism is at an early stage of development.
      • e.g. applying gene therapy to an egg or embryo so that the organism develops with the characteristic correctly coded for by the gene - correct genotype, giving the correct phenotype.

Ethical issues and 'pros and cons'

  • Again we see positive examples of the use of genetic engineering, but there are, as ever!, issues and problems to solve concerning the application of genetic engineering - use of genetically modified (GM) products.
    • 1. This is new technology, new 'biotechnology' to be precise, and people quite rightly are concerned about e.g. GM crops, though curiously enough, I've never heard anybody express worries about GM produced insulin - the latest versions of which are produced by GM techniques!
      • BUT GM products have enormous potential to solve problems in e.g. increased yields in food production, treating genetic disorder diseases.
      • For people living in poorer less developed countries, the quantity and quality of food CAN be improved.
      • It is no incidence that people in developed countries, who have a relatively good diet to start with, are much more concerned about the use GM crops, than people in poorer countries, with their greater need for an improved food supply.
    • 2. There are concerns as to whether GM crops e.g. cereals or rice have the same nutrient contents (mineral ions, vitamins etc.) as non GM crops.
      • Are there are any risks to human health by eating GM food products?
      • Will there be an increase in food allergies?
    • 3. Are there any long-term effects from consuming GM modified meat, grain or vegetable products etc.?
      • By changing an organism's genome, you can't predict whether problems will emerge for future generations (crops or people!).
      • Are there any health issues? Any long-term effects on consuming GM produced foods.
      • Will there be any effects on food chains and ecosystems?
    • 4. Will GM plants spread and affect the local diversity of the farmland and environs.
      • e.g. Will GM plants becoming more successful than local plants?
      • Will this reduce biodiversity around fields and the countryside in general?
      • Will the abundance and variety of wild flowers and insects be affected?
    • 5. Will GM crops hybridise with other crops or grasses to produce new strains of plant, again, these could affect the original biodiversity of the local flora (plants) and fauna (animals).
    • 6. Points 4. and 5. have considerable implications e.g. if the transplanted genes from GM plants spread to other native plants, we do not know what genotypes will be formed and what will be the resulting phenotypes (gene expression)?
      • If we produce a GM herbicide resistant plant, what happens if the herbicide resistant gene enters the genome of a weed, will a herbicide resistant weed evolve (a 'superweed'), that is even more herbicide resistant than the crop! From an agricultural point of view, a bit scary!
      • By using GM plants we are introducing genes into the natural environment, over which we might not have as much control as we would like!
    • 7. There are concerns about the welfare of genetically engineered animals.
      • You can't accurately predict all the effects on an animal after its genome has been modified - you may produce one desired product, but are there other genetic consequences?
      • Many genetically modified embryos do not survive, and genetically modified animals, especially clones, can suffer from health issues.
    • 8. Use of GM applications raises ethical issues in some peoples minds
      • Some people argue we are interfering with nature and it is wrong to genetically modify organisms just for the benefit of human beings AND uncertainty are the long-term consequences.
      • Is it right to genetically engineer animals just to benefits us, and ignoring their real/potential health problems?
      • Will we start genetically engineering our offspring for a set of 'ideal' characteristics e.g. good looks, intelligence, athletic prowess phenotypes etc.

Thoughts on the world production of food

See also more detailed Food Security gcse biology revision notes

Food and the world's population

Lets start with some statistics - two graphs of population and energy use.

 

The graphs shows the acceleration of the world's population and therefore and increasing food demand.

Although I have no data myself on the world's total food production, but there are some graphs on ...

https://ourworldindata.org/yields-and-land-use-in-agriculture ...

which clearly show a similar pattern in agricultural production.

BUT how long can this be sustained?, and there millions (billions?) of undernourished people suffering from starvation and disease, primarily from lack of local food production for one reason or another e.g. climate conditions, war, overuse of soil using non-sustainable agricultural practice.

To minimise the effects of lack of food, everyone should have access to safe nutritious food - sufficient as well as providing a balanced diet - this concept is known as 'food security'.

Food security can be defined as "the state of having reliable access to a sufficient quantity of affordable, nutritious food".

GM crops can help, but it is only one approach to increasing food production:

As already describe above, some developments so far include:

genetically engineered crops can be designed to be pest resistant and survive in drought conditions,

and crops can be GM designed to combat certain nutrient deficiencies e.g. increasing the content of a chemical in 'Golden Rice' that helps make Vitamin A in the body.

However, there are still issue of concern where GM is of little help:

Poor quality soil lacking in nutrients or water means crops will fail, even if they are GM.

Hunger exists where people cannot afford to buy food, even if it is available, therefore you need political and economic strategies to tackle poverty and improve/make fairer the economy and maybe import food too.

There is a danger that the agricultural production of a country might be too dominated by multinational companies that manufacture the GM seeds.

 

Other methods of increasing food production

GM crops are not the complete answer and neither should they always the 'first choice' in the future.

There are reason for lack of food which GM cannot do little about e.g.

Poor soil can be improved by application of fertilisers, but not overuse, which causes environmental problems.

You can control disease and insect without using GM crops and/or herbicides and pesticides.

You can use biological methods to control pests - deploying other organisms to reduce pest numbers which can act as predators or parasites.

These biological methods can be more sustainable than chemical pesticides, so less harmful to the environment.

See also more detailed Food Security gcse biology revision notes

 


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Typical learning objectives for this page

  • Know and understand that genes can also be transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.

    • Know that new genes can be transferred to crop plants.

    • Crops that have had their genes modified in this way are called genetically modified crops (GM crops).

    • Examples of genetically modified crops include ones that are resistant to insect attack, viruses, fungi or to herbicides.

      • This is all about increasing the quantity and quality of crops - insert genes into the plant's genome to increase the size and the quality of the grain.

        • Similarly, you can do the same for fruit plants to increase the quality (e.g. taste) and size of fruit.

      • Large quantities of crops are lost to disease and insect attack, so it make economic sense in principle.

      • One practical example is that if you can make a crop resistant to a herbicide that is used to kill weeds - weeds that compete for the soil nutrients, then you can kill the weeds by spraying without damaging the crops.

      • You can produce plants (fruit or grain) that are also resistant to diseases and insect attack to improve crop yields.

      • You can genetically engineer sheep to produce substances like drugs in their milk, which are used to treat certain human diseases.

    • Genetically modified crops generally show increased yields.

  • Appreciate concerns about GM crops include the effect on populations of wild flowers and insects, and uncertainty about the effects of eating GM crops on human health.

    • There is considerable public concern about GM crops eg are they harmful, are they as nutritious, are they reducing biodiversity, will they spread and multiply at the expense of native plants - out-compete for nutrients, will they cross-bread with native plants changing the gene pool,

    • GM crops of rice, and other basic grown foods, are seen as an economic way of feeding the growing poor populations of third world countries.

      • The idea behind GM crops is to increase yields and increase nutrition.

      • You can insert genes into crop cells so that they contain particular nutrients, whose deficiency can cause ill-health, or engineer a strain of wheat to contain more protein if meat is scarce.

      • So there are lots of possibilities and lots of controversies - so 'watch this GM space'

  • In the context of genetic engineering, be able to explain the role of the scientific community in validating new evidence, including the use of:
    • a) scientific journals - enable new findings on genetic engineering to be communicated to other scientists working in the same areas of science, so ideas and knowledge are widely spread AND other scientists can check whether the research is valid eg do other scientists get the same results? do other scientists draw the same conclusions? do other scientists agree with, and find the theory valid?
    • b) the peer review process - a sort of refereeing system, research papers on genetic engineering are read and checked by people competent to understand the contents of research papers (their peers) - this ensures standards are high in terms of 'good scientific practice'.
    • c) scientific conferences enable scientists to meet and present and discuss their findings on genetic engineering, compare their work, listen to new ideas, get ideas to take back to their own research project. Its also a forum for other scientists to hear about research which isn't necessarily exactly their own specialist field, but broadens their own knowledge of related fields of science e.g. genetic engineering.

 


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