Recombinant DNA (CIE A Level Biology)

• 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