This how it works covers How It Works: Restriction Enzymes, Ligase, and Vectors within Genetic Engineering for GCSE Biology. Genetic modification, gene therapy, and biotechnology applications It is section 4 of 11 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
How It Works: Restriction Enzymes, Ligase, and Vectors
Genetic engineering relies on precise molecular tools to cut, carry, and insert genes. Here is the detailed mechanism:
- Identify the gene: Scientists locate the gene that codes for the desired protein — for example, the human insulin gene found on chromosome 11.
- Cut with restriction enzymes: Restriction enzymes act as molecular scissors. Each restriction enzyme recognises a specific short DNA sequence (restriction site) and cuts through the double strand at that point, leaving "sticky ends" — short single-stranded overhangs that allow complementary DNA to join on.
- Prepare the vector: A plasmid (a small circular ring of bacterial DNA used as a vector) is cut open with the same restriction enzyme, giving it the same sticky ends.
- Insert the gene: The gene with sticky ends is mixed with the open plasmid. Complementary base pairing causes the sticky ends to join. DNA ligase enzyme then permanently seals (ligates) the joins, creating a recombinant plasmid containing the human gene.
- Transform the host organism: The recombinant plasmid is transferred into bacteria (e.g., Escherichia coli). The bacteria take up the plasmid — this process is called transformation.
- Expression and harvest: The bacteria transcribe and translate the inserted gene, producing the desired protein. Bacteria are cultured in large fermenters; the protein is extracted and purified. For insulin production, this replaced the older method of extracting insulin from pig or cow pancreases.
Practice questions for Genetic Engineering
Which of the following is a benefit of genetic engineering?
A genetic engineer uses a gene from one organism to introduce a desirable characteristic into another organism. This process is an example of which type of genetic engineering?
Quick recall flashcards
How is insulin produced using genetic engineering?
The human insulin gene is inserted into bacterial plasmids. The bacteria are grown in large fermenters and produce human insulin protein. This insulin is then purified for use by diabetics. Before this, pig or cow insulin (slightly different) was used.
What is genetic engineering?
The direct modification of an organism's genome by inserting a gene from another organism (or a modified gene) to give it a new or altered characteristic. The resulting organism is called a genetically modified (GM) organism.