DNA cloning is the starting point for many genetic engineering approaches to biotechnology research.
Large amounts of DNA are needed for genetic engineering. Multiple copies of a piece of DNA can be made either by using polymerase chain reaction (PCR) or by cloning DNA in cells.
How is DNA cloned in cells?
To get multiple copies of a gene or other piece of DNA you must isolate, or ‘cut’, the DNA from its source and then ‘paste’ it into a DNA vector that can replicate (or copy) itself.
The four main steps in DNA cloning are:
Step 1. The chosen piece of DNA is ‘cut’ from the source organism using restriction enzymes.
Step 2. The piece of DNA is ‘pasted’ into a vector and the ends of the DNA are joined with the vector DNA by ligation.
Step 3. The vector is introduced into a host cell, often a bacterium or yeast, by a process called transformation. The host cells copy the vector DNA along with their own DNA, creating multiple copies of the inserted DNA.
Step 4. The vector DNA is isolated (or separated) from the host cells’ DNA and purified.
DNA that has been ‘cut’ and ‘pasted’ from an organism into a vector is called recombinant DNA. Because of this, DNA cloning is also called recombinant DNA technology.
What is cloned DNA used for?
DNA cloning is used to create a large number of copies of a gene or other piece of DNA. The cloned DNA can be used to:
- Work out the function of the gene
- Investigate a gene’s characteristics (size, expression, tissue distribution)
- Look at how mutations may affect a gene’s function
- Make large concentrations of the protein coded for by the gene
What other types of cloning are there?
The term ‘cloning’ is also used to describe other laboratory processes:
- Reproductive cloning is the process of making a genetically identical copy of an organism.
- Therapeutic cloning is the process of making multiple copies of a cell to treat a disease.
