CIE A Level Biology复习笔记19.2.4 Gene Technology in Medicine

• The use of gene technology (genetic screening and gene therapy) in medicine is becoming more common
• Genetic screening in medicine is being used to:
  • Allow people with a family history of a genetic disease to have their DNA analysed to determine if they are at risk
  • Carry out pre-implantation genetic diagnosis (PGD) – embryos that are created outside the body (with the IVF procedure) have their DNA analysed, which allows for embryos that are not carrying a harmful allele that would cause the disease, to be chosen for implantation
• Gene therapy is being used in medicine for introducing corrected copies of genes into patients with genetic diseases (eg. cystic fibrosis, haemophilia, severe combined immunodeficiency)

Genetic screening

• There are many social and ethical considerations for genetic screening, which include:
  • Being able to take preventative measures (e.g. elective mastectomy when BRCA1 and BRCA2 are detected) - giving individuals control to prevent illness
  • Using pre-implantation genetic diagnosis to select embryos that do not carry faulty disease-causing alleles. This could lead to the fear of ‘‘designer babies’ being created (this includes creating/choosing embryos with tissue matches to older siblings). Pre-implantation genetic diagnosis can be carried out during in-vitro fertilisation (IVF); cells are extracted from the embryo in an embryo biopsy and genetically screened in order to preselect the embryos without faulty alleles
  • Using genetic counsellors to help people understand their choices and make informed decisions (eg. financial costs, whether termination of fetus is appropriate if quality of life is poor)
  • Risk of miscarriage (which has emotinal consequences) due to the procedures used to collect DNA which are not 100% risk-free
    • Amniocentesis – is used to obtain a sample of amniotic fluid using a hypodermic needle at 15 to 16 weeks of pregnancy
    • Chorionic villus sampling – is used to obtain a small sample of the placenta using a needle between 10 and 13 weeks of pregnancy

• Choosing to terminate a pregnancy (therapeutic abortion) because the embryo has a genetic disorder (eg. Thalassaemia or cystic fibrosis) or even terminating the embryo due to a minor ‘defect’ that could have seen the child lead an almost normal life
• Being able to make informed reproductive decisions (eg. Thalassaemia)
• Determining whether it is best to know the risk of having a disease, especially when there is no cure (eg. Huntington’s)
• Deciding at what age screening should begin eg. whether parents should be able to choose for their children to be screened
• The possibility of stigmatization and discrimination. The person may feel stigmatized if they have the disease or discriminated against by health insurers or employers
• Confidentiality of the data collected – who will have the right to view the results obtained

Social & ethical considerations of using gene therapy

• The social and ethical considerations of using gene therapy include:
  • The potential for side effects that could cause death (eg. the children who were treated for SCID developed leukaemia)
  • Whether germline gene therapy (the alteration of genes in egg and sperm cells which results in the alteration being passed onto future generations) should be allowed – it could be a cure for a disease or it could create long-term side effects
  • The commercial viability for pharmaceutical companies – if it is a rare disease, the relative small number of patients may not mean that the companies will make a profit (eg. Glybera – a gene therapy for lipoprotein lipase deficiency is no longer produced as there were too few patients)
  • The expense of treatments as multiple injections of the genes may be required if the somatic cells are short-lived (eg. severe combined immunodeficiency). This may make the cost of gene therapy accessible to a limited number of people
  • The possibility that people will become less accepting of disabilities as they become less common
  • Who has the right to determine which genes can be altered and which cannot (eg. should people be allowed to enhance intelligence or height)
  • Another method of enhancing sporting performances unfairly through gene doping. This is where the genes are altered to give an unfair advantage eg. to provide a source of erythropoietin (the hormone that promotes the formation of red blood cells)