Molecular biology: Gene cloning
Author: Prof Marinda Oosthuizen
Licensed under a Creative Commons Attribution license.
What is gene cloning?
In a gene cloning experiment, a fragment of DNA (containing
The process of molecular cloning involves isolating a DNA
the gene to be cloned) is inserted into a circular DNA
sequence of interest and generating multiple copies of it in an
molecule called a vector, to produce a recombinant DNA
organism, usually a bacterium that is capable of growth over
molecule. The vector acts as a vehicle that transports the
extended periods. Large quantities of the DNA molecule can
gene into a host cell, which is usually a bacterium, although
then be isolated in pure form for detailed molecular analysis.
viruses and various living cells can be used. Within the host
cell the vector multiplies, producing numerous identical
copies not only of itself, but also of the gene that it carries.
When the host cell divides, copies of the recombinant DNA
molecule are passed to the progeny and further vector
replication takes place. After a large number of cell divisions,
a colony or clone of identical host cells is produced. Each cell
in the clone contains one or more copies of the recombinant
DNA molecule; therefore the gene carried by the recombinant
molecule, is now said to be cloned.
Is cloning an organism the same as cloning a gene? These
days, one regularly hears about the cloning of animals
(sheep, cattle, horses, mice, and even house pets) in the
news. From time to time, you may even have heard about
researchers cloning, or identifying, genes that are responsible
for various medical conditions or traits. But, what is the
difference?
 Cloning an animal, or any other organism, refers to
making an exact genetic copy of that organism by
using artificial embryo twinning or somatic cell nuclear
transfer.
 Cloning a gene means the isolation of an exact copy of a
single gene from the entire genome of an organism. This
usually involves copying the DNA sequence of that gene
into a smaller, more accessible piece of DNA, such as a
plasmid. This makes it easier to study the function of the
individual gene in the laboratory.
Adapted from:
http://gslc.genetics.utah.edu/units/cloning/whatiscloning/