Genetic technology and medicine

Genetic technology allows products specific to humans to be made.

Examples of juman proteins produced by genetic technology are:

• human growth hormone
• thyroid stimulating hormone
• factor VIII - a blood clotting protein

Advantages of using bacteria, yeasts and cultures of mammalian cells to produce these protein are:

• these cells have simple nutritional requirements
• large volumes of product are produced
• the production facilities do not require much space and the processes can be carried out almost anywhere in the world

There are few ethical and practical problems, because proteins do not have to be extracted from animal sources or by collecting blood from many donors

The disadvantages are:

• bacteria do not modify their proteins in the same way that eukaryotes do

Therefore is is much better to use eukaryotic cells to produce human proteins

• genetically modified hamster cells are used by several companies to produce factor VIII
• this protein is essential for blood clotting, and people who cannot make it are said to have haemophilia
• the human gene for making factor VIII has been inserted into hamster kidney and ovary cells which are then cultured in fermenters
• the cells constantly produce factor VIII which is extracted and purified before being used to treat people with haemophilia
• these people need regular injections and before the availability of recombinant factor VIII it came from donated blood
  • using donated blood carried risks of infection - like HIV

.

• high yields of the enzyme adenosine deaminase (ADA), used to treat severe combined immunodeficiency disease (SCID), are made by a genetically modified insect larva, the cabbage looper moth caterpiller
• this enzyme is administered to patients while they are waiting for gene therapy or when gene therapy is not possible

Some proteins are even produced by transgenic animals. Sheep and goats have been genetically modified to produce human proteins in their milk:

• human antithrombin is produced by goats - this protein is used to stop blood clotting
• human alpha-antitrypsin is produced by sheep - this is used to treat people with emphysema

Genetic screening

• genetic screening  is the analysis of a person's DNA to check for the presence of a particular allele
• it can be done in adults, fetus or embryo in the uterus, or in a newly formed embryo produced by vitro fertilisation
• a woman with a family history of breast cancer may choose to be screened for the faulty alleles of the genes Brca -1 and Brca - 2 which considerably increase an individual's chance of developing breast cancer
  • should the results be positive, the woman may elect to have her breasts removed (elective mastectomy) before such cancer appears

• In 1989, the first 'designer baby' was created
• officially known as pre-implantation genetic diagnosis (PGD), the technique involved mising the father's sperm with the mother's eggs (oocytes) in a dish - a 'normal' IVF procedure
• at the eight-cell stage, one of the cells from the tiny embryo was removed
• the DNA in the cell was analysed…