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
Overview of the Steps of Genetic Engineering Diagram
An overview of the steps taken to genetically engineer an organism (in this case bacteria are being genetically engineered to produce human insulin)
Analogy: Essay Writing and Recombinant DNA
- Creating transgenic organisms is rather like copying and pasting some text from one of your previous essays into the one that you are currently writing
- If you believe that the essay that you are currently writing can be strengthened by the use of some text from another essay that you have previously written, it is a common practice to use the computer’s copy-and-paste function to transfer text in one block without having to retype it
- This has similar features to genetic modification in the creation of a transgenic organism
| Stage |
Essay writing |
Genetic modification |
| Identification | Identify useful text from the first essay | Identify a useful gene from one organism |
| Same language? | Yes - English to English | Yes - universal genetic code (A, C, G, and T) |
| Identify start point | Place the cursor at the beginning of the text to be copied | Find the restriction site at the beginning of the gene to be copied |
| Select material to be copied | Click and drag down to the end of the text to be copied | Find the restriction site at the end of the gene to be copied |
| Cut | Right-click-copy or ctrl-c | Use restriction endonucleases |
| Vector | Computer clipboard (memory) | e.g. a plasmid |
| Select the destination | Place the cursor at the insertion point | Restriction endonuclease to open up the DNA at the insertion point |
| Paste | Right-click-paste or ctrl-v | Ligase enzyme or merge plasmid into destination genome |
| Function check | Does the pasted text convey the point I wish to make, in the right place? Does it fit with the text on either side of it? | Is the recombinant gene being expressed effectively in the transgenic organism? Are there no detrimental side effects? |
| Ethical considerations | Have I pasted my own text and not plagiarised somebody else's work? | Many ethical considerations (see later revision notes) |
Exam Tip
In your answer about genetic engineering you should remember to include the names of the enzymes (restriction endonucleases, reverse transcriptase, ligase) involved in genetic engineering and mention that markers (genes which can be identified) and vectors (transfer the desired gene) are also used.
