Recombinant DNA
- The genetic code is universal, meaning that almost every organism uses the same four nitrogenous bases – A, T, C & G. There are a few exceptions
- This means that the same codons code for the same amino acids in all living organisms (meaning that genetic information is transferable between species)
- Thus scientists have been able to artificially change an organism's DNA by combining lengths of nucleotides from different sources (typically the nucleotides are from different species)
- The altered DNA, with the introduced nucleotides, is called recombinant DNA (rDNA)
- If an organism contains nucleotide sequences from a different species it is called a transgenic organism
- Any organism that has introduced genetic material is a genetically modified organism (GMO)
Principles of Recombinant DNA Diagram
Illustration of a maize plant that has recombinant DNA from a bacterium (DNA from Bacillus thuringiensis)
- The bacterium species Bacillus thuringiensis contains a gene that codes for a toxic compound (called Bt toxin) that can kill crop pests
- The maize plant does not contain this gene naturally
- The bacterial gene can be recombined into the genome of the maize
- This creates a variety of maize plants that can produce the toxin itself
- This gives the transgenic maize pest resistance, which is of great value in agriculture
Examiner Tip
It is because of the universal genetic code that recombinant DNA can be formed. All forms of life use the same genetic code, which is the strongest piece of evidence for evolution. Remember, the genetic code is the basis for storing instructions that, alongside environmental influences, dictate the behaviour of cells and as a result, the behaviour of whole organisms.
