Genetic Engineering (Cambridge (CIE) A Level Biology): Revision Note

Genetic engineering explained

• Genetic engineering is a technique used deliberately to modify a specific characteristic (or characteristics) of an organism

• The technique involves removing a gene (or genes) with the desired characteristic from one organism and transferring the gene (using a vector) into another organism where the desired gene is then expressed

• The genetically engineered organism will then contain recombinant DNA and will be a genetically modified organism (GMO)

• For an organism to be genetically engineered the following steps must be taken:

  • Identification of the desired gene

  • Isolation of the desired gene by:

    • Cutting from a chromosome using enzymes (restriction endonucleases)

    • Using reverse transcriptase to make a single strand of complementary DNA (cDNA) from mRNA

    • Creating the gene artificially using nucleotides

  • Multiplication of the gene (using polymerase chain reaction - PCR)

  • Transfer into the organism using a vector (e.g. plasmids, viruses, liposomes)

  • Identification of the cells with the new gene (by using a marker), which is then cloned

• Genetic engineers need the following to modify an organism:

  • Enzymes (restriction endonucleases, ligase and reverse transcriptase)

  • Vectors - used to deliver genes into a cell (eg. plasmids, viruses and liposomes)

  • Markers - genes that code for identifiable substances that can be tracked (e.g. GFP - a green fluorescent protein which fluoresces under UV light or GUS - β-glucuronidase enzyme which transforms colourless or non-fluorescent substrates into products that are coloured or fluorescent)

• Genetic engineering is being used in the new field of science called synthetic biology

  • This is an area of research that studies the design and construction of different biological pathways, organisms and devices, as well as the redesigning of existing natural biological systems