Chapter 18: Genetic
Engineering
Leaving Certificate Biology
Higher Level
Genetic Engineering
• Genetic engineering is the manipulation and
alteration of genes in basic and applied
research
– Involves the introduction of foreign genes into an
organism’s genetic material using plasmids and
restriction enzymes
– Genes can be transferred between organisms that
are evolutionary very distant – e.g. humans and
bacteria
– DNA that contains a foreign gene is called
recombinant DNA
Genetic Engineering
• The following steps are involved in producing
recombinant DNA:
1. Isolation: removal of DNA that carries gene of interest
and removal of vector DNA (e.g. plasmids from E. coli)
2. Transformation: is the uptake and insertion of foreign
DNA into the DNA of the host – involves:
• Cutting – human DNA and bacterial plasmid are both cut by
specific restriction enzyme. Human DNA now has sticky ends
• Ligation (splicing) – DNA ligases help the human DNA fragments
to insert into the open plasmid in the correct orientation
3. Expression: activation of the gene to produce a
specific protein (e.g. human insulin)
Applications of Genetic
Engineering
• Plant: crop plants can be genetically modified by
inserting a bacterial gene that gives them
resistance to specific herbicides
• Animal: sheep have been genetically modified
to carry the human blood clotting factor gene
such that it can only be expressed in the
mammary glands – then the human blood
clotting factor is extracted from the sheep’s milk
• Microorganism: bacteria have been genetically
modified to carry the human insulin gene so that
they can produce large amounts of the protein
insulin in culture