8 Flashcards
Describe gene therapy
● Introduction of new DNA into cells, often containing healthy / functional alleles
● To overcome effect of faulty / non-functional alleles in people with genetic disorders
Suggest some issues associated with gene therapy
● Effect is short lived as modified cells (eg. T cells) have a limited lifespan → requires regular treatment
● Immune response against genetically modified cells or viruses due to recognition of antigens
● Long term effect not known - side effects eg. could cause cancer
○ DNA may be inserted into other genes, disrupting them → interfering with gene expression
Suggest why humanitarians might support recombinant DNA technology
● GM crops increase yields → increased global food production → reduced risk of famine / malnutrition
● Gene therapy has potential to cure many genetic disorders
● ‘Pharming’ makes medicines available to more people as medicines cheaper
Suggest why environmentalists and anti-globalisation activists might oppose recombinant DNA technology
● Recombinant DNA may be transferred to other plants → potential herbicide resistant ‘superweeds’
● Potential effects on food webs eg. affect wild insects → reduce biodiversity
● Large biotech companies may control the technology and own patents
Suggest how recombinant DNA technology can be useful
Medicine
● GM bacteria produce human proteins (eg. insulin for type 1 diabetes) → more ethically acceptable than using animal proteins and less likely to cause allergic reactions
● GM animals / plants produce pharmaceuticals (‘pharming’) → cheaper
● Gene therapy
Agriculture and Industry
● GM crops resistant to herbicides → only weeds killed when crop sprayed with herbicide
● GM crops resistant to insect attack → reduce use of insecticide
● GM crops with added nutritional value
● GM animals with increased growth hormone
● GM bacteria produce enzymes used in industrial processes and food production
Describe the regulation of translation by RNA interference
- Small interfering RNA (siRNA) or micro-RNA (miRNA) is incorporated into/ binds to a protein, forming an RNA-induced silencing complex (RISC)
- Single-stranded miRNA / siRNA within RISC binds to target mRNA with a complementary base sequence
- This leads to hydrolysis of mRNA into fragments which are then degraded OR prevents ribosomes binding
- Reducing / preventing translation of target mRNA into protein
Evaluate the use of stem cells in treating human disorders
For
✓ Can divide and differentiate into required healthy cells, so could relieve human suffering by
saving lives and improving quality of life
✓ Embryos are often left over from IVF and so would otherwise be destroyed
✓ iPS cells unlikely to be rejected by patient’s immune system as made with patient’s own cells
✓ iPS cells can be made without destruction of embryo and adult can give permission
Against
X Ethical issues with embryonic stem cells as obtaining them requires destruction of an
embryo and potential life (embryo cannot consent)
X Immune system could reject cells and immunosuppressant drugs are required
X Cells could divide out of control, leading to formation of tumours / cancer
Explain how stem cells can be used in the treatment of human disorders
● Transplanted into patients to divide in unlimited numbers
● Then differentiate into required healthy cells (to replace faulty / damaged cells)
Examples:
● Potential treatment of Type 1 diabetes by creating healthy islet cells that produce insulin
● Bone marrow stem cell transplant for SCD / blood cancers
1. Destroy patient’s bone marrow before treatment → so no faulty cells are produced
2. Transplant stem cells from healthy person → divide and differentiate into healthy cells
Explain how induced pluripotent stem (iPS) cells are produced
- Obtain adult somatic (body) cells (non-pluripotent cells or fibroblasts) from patient
- Add specific protein transcription factors associated with pluripotency to cells so they express genes associated with pluripotency (reprogramming)
○ Transcription factors attach to promoter regions of DNA, stimulating or inhibiting transcription - Culture cells to allow them to divide by mitosis
Explain the role of increased oestrogen concentrations in the development of some (oestrogen receptor-positive) breast cancers
- Some breast cancers cells have oestrogen receptors, which are inactive transcription factors
- If oestrogen concentration is increased, more oestrogen binds to oestrogen receptors,
forming more oestrogen-receptor complexes which are active transcription factors - These bind to promoter regions of genes that code for proteins stimulating cell division
- This increases transcription / expression of these genes, increasing the rate of cell division
