Explain how gene transfer, expression and purification in genetically modified host cells produce recombinant human proteins in Cambridge A Level Biology questions, using mark-scheme evidence.
One cause of the genetic disease severe combined immunodeficiency (SCID) is a mutation in the ADA gene. This mutation results in a deficiency of the enzyme adenosine deaminase (ADA).
Although ADA is found throughout the body, it is especially active in lymphocytes. The absence of functional ADA causes the build-up of toxic metabolites that kill lymphocytes and damage organs.
Babies are often diagnosed with SCID by six months old. Treatment can greatly improve the life expectancy of children with SCID.
Some treatment options are available.
- Enzyme replacement therapy with recombinant human ADA made by genetically modified (GM) Escherichia coli. Weekly intra-muscular injections are given.
- Bone marrow transplant if a well-matched donor, such as a close relative, can be found.
- Gene therapy.
Suggest and explain why it may be more appropriate to use enzyme replacement therapy to treat SCID instead of a bone marrow transplant.
any three from:
1 donor not needed ;
2 immediate effect ;
3 idea that easy to administer treatment ;
4 no immune response / no rejection ;
5 less invasive ;
6 AVP ;
e.g. lower risk to health / cheaper / quicker