In GCSE biology, the features of bacteria that make them ideal for industrial and genetic processes include:
- Rapid reproduction
- Presence of plasmids – circular DNA molecules that can be transferred easily between bacteria
- Simple biochemistry – easy to understand and alter
- Ability to make complex molecules – bacteria can produce molecules that can be used medicinally
- Lack of ethical concerns in their culture
Many useful products are made by fermentation – which involves growing bacteria or fungus (e.g. yeast) on a large scale. Usually in GCSE biology curriculum, some of these useful products include:
- Antibiotics and other medicines
- Single-cell protein – such as mycoprotein which is used in meat substitute products
- Enzymes for food processing, for example chymosin as a vegetarian substitute for rennet
- Enzymes for commercial products, such as washing powders and to make biofuels
In the GCSE biology curriculum, in genetic modification, a gene is transferred from one organism to another where it continues to work:
- Isolation and replicating the required gene
- Putting the gene into a suitable vector (virus or plasmid)
- Using the vector to insert the gene into a new cell
- Selected the modified individuals
Examples of the application of genetic modification include:
- Bacteria synthesis of medicines e.g. insulin
- Herbicide resistance in crop plants – by creating crops with resistance to a herbicide, the farmer can use that herbicide to kill weeds without destroying the crop
Genetic testing may be used to find out if an individual has a genetic disease – a disease which they have inherited and which is a result of a defect in their DNA.
In GCSE biology, to investigate a person’s DNA, white blood cells are used because they are easy to obtain from a blood sample, and unlike red blood cells they have a nucleus containing the DNA.
- Isolation of DNA from white blood cells
- A small quantity of blood has chemicals added it – the chemicals split open the red cells. The DNA is collected and then replicated (more copies of it are made) so that there is enough to test. The DNA is then broken up into smaller sections using enzymes and put onto a special gel. An electrical current is applied, and the pieces of DNA separate out along the gel.
- Gene probe (marker)
- Gene probes are created that are mirror copied of the target allele or microsatellite region – the gene probes are attached to a fluorescent chemical that emits ultraviolet light. If the target segment of DNA is present in the DNA sample, the gene probe will attach to it.
- Adding the gene probe to the sample DNA
- The separated pieces of DNA on the gel are ‘blotted’ to split the DNA into single strands. The gene probe is added and if the gene the scientist is searching for is present, the gene probe will bind to it because it has a complementary base sequence to the gene being investigated. This process is called Southern blotting
- Using UV light
- The gel is then viewed under UV light. If the gene is present, the gel will glow at that point. The gene has therefore been identified as being present in the person’s DNA.
Pictures from https://getrevising.co.uk/resources/biology_b7_ocr_21st_century & https://www.cdc.gov/genomics/gtesting/genetic_testing.htm & strikingly.com
End of the topic!
Drafted by Gina (Biology)