Page 62 - Cell biology PDG 2024

CHAPTER 6

GENETIC ENGINEERING

Genetic engineering is the artificial handling and recombination of
nucleic acid (DNA or RNA) to modify an organism. It includes
recombinant DNA technology (or gene cloning), in which DNA from two
different sources are combined together either within cells or in vitro and
are then inserted into a host organisms in which they are able to
propagate
The discovery of restriction enzymes in 1968 by the microbiologist Swiss
Werner Arber made recombinant DNA technology possible. The next
year the American microbiologist Hamilton O. Smith purified type II
restriction enzymes that have the ability to cleave a specific site within
the DNA
The recombinant DNA technology involves the insertion of foreign genes
into the plasmids (vector) of a bacteria. These bacterial cells are now
called competent cells
Plasmids: they are small rings of DNA that are not part of the bacterium’s
chromosome but capable of directing protein synthesis of the bacteria.
They can also reproduce and pass to the daughter bacterial cell. So, by
inserting a foreign DNA into the plasmid of a bacteria we can obtain
many copies of the inserted gene
So first both the foreign DNA and the plasmid are cut by the same
restriction enzyme to produce sticky ends in both, then they are put
together to bind by means of ligase enzyme. Now the plasmid carrying
the foreign DNA is called recombinant DNA that will be inserted in a
bacterial cell to make many copies of it (cloning).

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