CIE A Level Biology (9700) 2019-2021

Revision Notes

19.2.1 Recombinant Human Proteins

Recombinant Human Proteins

  • DNA that has been altered by introducing nucleotides from another source is called recombinant DNA (rDNA)
  • If the organism contains nucleotides from a different species it is called a transgenic organism
  • Any organism that has introduced genetic material is a genetically modified organism (GMO)
  • Recombinant DNA has been used to produce recombinant proteins (RP), thus recombinant proteins are manipulated forms of the original protein
  • Recombinant proteins are generated using microorganisms such as bacteria, yeast, or animal cells in culture. They are used for research purposes and for treatments (eg. diabetes, cancer, infectious diseases, haemophilia)
  • Most recombinant human proteins are produced using eukaryotic cells (eg. yeast, or animal cells in culture) rather than using prokaryotic cells, as these cells will carry out the post-translational modification (due to presence of Golgi Apparatus and / or enzymes) that is required to produce a suitable human protein
  • The advantages of genetic engineering organisms to produce recombinant human proteins are:
    • More cost-effective to produce large volumes (i.e. there is an unlimited availability)
    • Simpler (with regards to using prokaryotic cells)
    • Faster to produce many proteins
    • Reliable supply available
    • The proteins are engineered to be identical to human proteins or have modifications that are beneficial
    • It can solve the issue for people who have moral or ethical or religious concerns against using cow or pork produced proteins

Insulin

  • In 1982, insulin was the first recombinant human protein to be approved for use in diabetes treatment
  • Bacteria plasmids are modified to include the human insulin gene
    • Restriction endonucleases are used to cut open plasmids and DNA ligase is used to splice the plasmid and human DNA together
  • These recombinant plasmids are then inserted into Escherichia coli by transformation (bath of calcium ions and then heat or electric shock)
  • Once the transgenic bacteria are identified (by the markers), they are isolated, purified and placed into fermenters that provide optimal conditions
  • The transgenic bacteria multiply by binary fission, and express the human protein – insulin, which is eventually extracted and purified
  • The advantages for scientists to use recombinant insulin are:
    • It is identical to human insulin, unless modified to have different properties (eg. act faster, which is useful for taking immediately after a meal or to act more slowly)
    • There is a reliable supply available to meet demand (no need to depend on availability of meat stock)
    • Fewer ethical, moral or religious concerns (proteins are not extracted from cows or pigs)
    • Fewer rejection problems or side effects or allergic reactions
    • Cheaper to produce in large volumes
    • That it is useful for people who have animal insulin tolerance

Factor VIII

  • Factor VIII is a blood-clotting protein that haemophiliacs cannot produce
  • Kidney and ovary hamster cells have been genetically modified to produce Factor VIII
  • Once modified these recombinant cells are placed into a fermenter and cultured
  • Due to the optimal conditions in the fermenter, the hamster cells constantly express Factor VIII which can then be extracted and purified, and used as an injectable treatment for haemophilia
  • The advantages for scientists to use recombinant Factor VIII are:
    • Fewer ethical, moral or religious concerns (proteins are not extracted from human blood)
    • Less risk of transmitting infection (eg. HIV) or disease
    • Greater production rate

Adenosine deaminase

  • Adenosine deaminase (ADA) is an enzyme used to treat the inherited condition called Adenosine Deaminase Deficiency
  • ADA Deficiency is a common cause of Severe Combined Immunodeficiency (SCID)
  • This is because the immune system is damaged
  • The larva of the cabbage looper moth has been genetically modified (using a virus vector) to produce the enzyme adenosine deaminase so that it can be used as a treatment whilst the patients wait for gene therapy or when gene therapy is not possible
  • The advantages for scientists to use recombinant adenosine deaminase are:
    • Fewer ethical, moral or religious concerns (proteins are not extracted from cows)
    • Less risk of transmitting infection or disease (from cows)
    • More reliable production of enzyme
    • Faster to produce many proteins

Exam Tip

Learn how recombinant human insulin is produced and the advantages of recombinant human insulin being used to treat diabetes.

Author: Catherine

Cate has over 20 years’ experience teaching Biology to IGCSE, IB and A-level students in seven different countries across Asia, Europe, North America and the Middle East. This has given her a fine appreciation of different cultures, places and teaching methods. Cate has a keen interest in producing Biology revision resources that will help students engage with the subject.
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