The discovery of the structure of DNA by Watson and Crick in the early 1950s and discoveries since have
led to many applications of gene technology in areas of medicine, agriculture and forensic science. This
section relies heavily on prior knowledge of DNA structure and protein synthesis studied in the section on
Nucleic acids and protein synthesis. Where possible, candidates should carry out practical work using
electrophoresis, either with DNA or specially prepared dyes used to represent DNA or proteins.
Principles of genetic technology
Genetic engineering involves the manipulation of naturally occurring processes and enzymes.
Genome sequencing gives information about the location of genes and provides evidence for the
evolutionary links between organisms.
Recombinant DNA: DNA made by joining pieces from 2 or more different sources
Genetic engineering
Genetic engineering involves the extraction of genes from one organism, or the synthesis of genes, in
order to place them into the DNA of another organism (of the same or another species) to form
recombinant DNA. The genes need to be inserted in such a way that they will be expressed in the
genetically modified organisms (GMO)
Transgenic organism/ genetically modified organism (GMO)= The organisms which now expresses
the new gene.
Genetic engineering provides a way of overcoming barriers to gene transfer between species.
Gene transfer
1. Gene that is required is identified. May be cut from a chromosome, made from a chromosome,
made by mRNA by reverse transcription or synthesized from nucleotides.
2. multiple copies of a gene are made using technique PCR (cloning desired gene)
3. gene is inserted into a vector which delivers the gene to the cells of the organism. Eg vectors=
plasmids, viruses and liposomes.
4. the vector takes the gene into the cells
5. the cells that have the new gene are identified and cloned. Identify which organisms have been
successfully transformed (have copies of the desired gene)
6. Turning gene on so that the organism starts to make lots of protein coded for by the gene.
Need -
Enzymes, e.g. restriction endonuclease, ligase and reverse transcriptase
Vectors, including plasmids and viruses
Genes coding for easily identifiable substances that can be used as markers
Genetic engineering relies on the principle that when genes are transferred between species, the amino
acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.
As Dna takes the same form in all organisms therefore a gene and a bacterium will be transcribed and
translated in the same way as in a human cell.