Genetic Engineering Techniques (OCR A Level Biology)

Revision Note

Test yourself
Lára

Author

Lára

Last updated

Genetic Engineering Techniques

  • In order for an organism to be genetically engineered the following steps must be taken:
    • Identification of the DNA fragment or gene
    • Isolation of the desired DNA fragment (either using restriction enzymes, a gene machine or reverse transcriptase)
    • Multiplication of the DNA fragment (using polymerase chain reaction - PCR)
    • Transfer into the organism using a vector (e.g. plasmids, viruses, liposomes). Electroporation is used to encourage uptake of plasmid vectors.
    • Identification of the cells with the new DNA fragment (by using a marker), which is then cloned

  • Genetic engineers need the following 'tools' to modify an organism:
    • Enzymes
      • Restriction endonucleases - used to cut genes at specific base sequences (restriction sites). Different restriction enzymes cut at different restriction site
      • Ligase - used to join together the cut ends of DNA by forming phosphodiester bonds
      • Reverse transcriptase - Used to build double stranded DNA from single stranded RNA

    • Vectors - used to deliver DNA fragments into a cell
      • Plasmids - transfer DNA into bacteria or yeast
      • Viruses - transfer DNA into human cells or bacteria
      • Liposomes - fuse with cell membranes to transfer DNA into cells

    • Markers - genes that code for identifiable substances that can be tracked
      • Fluorescent markers e.g. green fluorescent protein (GFP) which fluoresces under UV light
      • Enzyme markers e.g. β-glucuronidase (GUS) enzyme which transforms colourless or non-fluorescent substrates into products that are coloured or fluorescent
      • Antibiotic resistance marker genes - The required gene sequence is inserted into a gene for antibiotic resistance. This inactivates the antibiotic resistance gene and therefore means that successfully transformed bacteria will be wiped out if exposed to the antibiotic. A replica plating method is then used to isolate the successfully transformed bacteria

Genetic engineering explained (1), downloadable AS & A Level Biology revision notes Genetic engineering explained (2), downloadable AS & A Level Biology revision notes Genetic engineering explained (3), downloadable AS & A Level Biology revision notes Genetic engineering explained (4), downloadable AS & A Level Biology revision notes

An overview of the steps taken to genetically engineer an organism (in this case bacteria are being genetically engineered to produce human insulin)

Examiner Tip

When answering questions about genetic engineering you should remember to include the names of any enzymes (restriction endonucleases, reverse transcriptase, ligase) involved and mention that markers (genes which can be identified) and vectors (transfer the desired gene) are also used.

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.