Flashcards in Genetic Technology in Medicine (Chapter 19) Deck (60)
How can human proteins be produced using recombinant DNA techniques?
Using bacteria, yeasts and cultures of mammalian cells
Name two human proteins produced by recombinant DNA techniques other than insulin
1) factor VIII (blood clotting protein)
2) adenosine deaminase (ADA)
What is the advantage of using bacteria, yeasts and cultures of mammalian cells in recombinant DNA techniques to produce human proteins?
1) these cells have simple nutritional requirements ∴ large volumes of the product are produced, the production facilities do not require much space and the processes can be carried out almost anywhere in the world
2) there are few practical and ethical problems bc proteins do not have to be extracted from animal sources or from blood collected from many human donors
What is the disadvantage of using bacteria to produce human proteins?
Bacteria do not modify their proteins in the same way as eukaryotes do ∴ it is much better to use eukaryotic cells to make human proteins
What is factor VIII?
A protein essential for blood clotting
What condition to people who cannot make factor VIII have?
What is used to produce factor VIII?
Genetically modified hamster cells
How are GM hamster cells used to produce factor VIII?
1) the human gene for making factor VIII is inserted into hamster kidney and ovary cells which are then cultured in fermenters
2) the cells constantly produce factor VIII which is extracted and purified before being used to treat people with haemophilia
3) these people need regular injections of factor VIII
What problem does recombinant factor VIII avoid?
The risk of infection from e.g. HIV when factor VIII used to come from donated blood
What is ADA?
An enzyme used to treat severe combined immunodeficiency disease (SCID)
What is used to make ADA?
Genetically modified insect larva of the cabbage looper moth caterpillar
When is ADA administered to patients?
While they are waiting for gene therapy
Where else are some proteins produced?
In the milk of transgenic animals
What two proteins are produced in the milk of transgenic animals?
1) human antithrombin (anti-blood clotting protein) in goat's milk
2) human alpha-antitrypsin (anti emphysema) in sheep's milk
What is genetic screening?
The analysis of a person's DNA to check for the presence of a particular allele
Who can genetic screening be carried out on
2) fetus or embryo in the uterus
3) a newly formed embryo formed by IVF
Give an example of how genetic screening can be used
- A woman with a family history of breast cancer could choose to be screened for the fault alleles of the gene Brca-1 and Brca-2, which considerably increase the chance of developing breast cancer
- If the results are positive for the faulty alleles, she can choose to have an elective mastectomy before the cancer appears
What is IVF?
When the mother's eggs are mixed with the father's sperm in a dish
What two techniques were used to make the first 'designer baby' in 1989?
Using pre-implantation genetic diagnosis (PGD) and IVF
How was the first 'designer baby' made?
1) at the 8-cell stage, one of the cells from the embryo was removed and its DNA analysed to predict whether or not the embryo would have a disease for which both parents were carriers e.g. haemophilia or sickle cell anaemia
2) embryos with the allele causing disease were discarded and the embryo without the allele was chosen for implantation
How have PGD and IVF been used since 1989?
To avoid pregnancies where the baby would have had Duchenne muscular dystrophy, thalassaemia, haemophilia or Huntington's disease
What does genetic testing leave the parents with if the embryo is found to have a genetic condition?
Very difficult decisions to make e.g. whether or not to have a termination of pregnancy
What two techniques can be used to screen a fetus for a genetic disease?
2) chronic villus sampling
(then parents can decide whether to terminate)
What are two problems with screening a fetus?
1) Some parents have decided to terminate just for a relatively minor 'defect' where the child could live a fairly normal life or when the child is not the sex they want
2) PGD has been used to select the sex of the embryo to implant - many think this sex preselection is totally unethical
- Used to obtain a sample of amniotic fluid at 15-16 weeks of pregnancy
- Samples are tested to check for the heath of the fetus and any chromosomal mutation
- When obtaining the sample, ultrasound scanning is used to choose a suitable position for the syringe needle away from the fetus, placenta and umbilical cord
Describe chronic villus sampling
- Used to get an earlier warning of any genetic abnormalities in the fetus at 10-13 weeks
- Chorion (small part of the placenta) is remove by a needle and tested for any genetic abnormalities
- There is a small (1-2%) increase in the risk of miscarriage
What is thalassaemia and why has its incidence increased significantly?
- A blood disease similar to sickle cell anaemia
- Its incidence has significantly decreased as a result of genetic screening and giving advice to parent carriers
What is a therapeutic abortion?
Termination a pregnancy for a medical reason
Why might it be difficult for someone to decide whether to be genetically screened for Huntington's disease?
- It is late onset, with no cure and just because the dominant allele is there, it does not mean that the disease will develop
- However, even if the disease does not develop, it could be passed down