(5) Medical applications of GM technology products including genetic modifications to the human genome

• (a) The production of human insulin by genetically modified bacteria (discussed in detail in Part 2).

  • 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.

• (b) 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!

• (c) Medical researchers are trying to develop genetic modification treatments for inherited diseases caused by faulty genes.

  • The idea is to insert correctly working genes (the normal correctly working allele) into the cells of people suffering from the disorder caused by alleles of faulty genes.

  • This technique is called gene therapy - a sort of allele replacement technique.

  • Gene therapy is at a very experimental stage, but much is hoped from this technique.

  • 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.

  • However, the following description describes one particular type of gene therapy involving cell exchange.

    • An example of a gene therapy procedure

    • A deactivated virus is used as a vector, but it is quite difficult to replace genes effectively.

    • (1) A normal human allele is inserted into the virus vector - the altered virus.

    • (2) Cells carrying the defective gene are removed from the patient.

    • (3) The altered virus is inserted into the cells removed from the patient.

    • (4) The modified cells are then injected back into the patient.

    • (5) Then, hopefully, the modified cells can then carry out their function correctly.

  • Problems encountered in gene therapy patients

    • An overactive immune response, which in some early cases was lethal - the modified cells were treated as foreign pathogens by the immune system.

    • Leukaemia cases occurred, probably due to the virus vector.

  • Genome editing

    • Genome editing is emerging as a potential biotechnology involving replacing or removing sections of DNA of an animals genome.

    • It is possible to do this using 'molecular scissors' and the technique is improving all the time.

      • (As I'm writing this in 2020, two female scientists have been awarded the Nobel Prize in Chemistry for their work in developing gene editing techniques. Emmanuelle Charpentier and Jennifer A. Doudna developed the Crispr tool, which can change the DNA of animals, plants and microorganisms with high precision.)

    • Note that any successful gene therapy cannot prevent the patient from passing on an inherited medical condition to their children.

      • It is only the patient's cells that are modified.

      • Any modification of the reproductive cells (male and female gametes) involves at least two immediate problems.

      • (i) Extremely technically difficult to do,

      • (ii) and poses major ethical problems as to the right to carry out such a procedure - 'designer babies'.

      • • This type of gamete gene therapy is not allowed by law.

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