What Is Biotechnology? - Biotechnology and Your Health: Pharmaceutical Applications - page 15

Cloning
Genes
Cloning a gene means making copies of the same DNA sequence. As
described above, this can be done with PCR. Another way scientists
clone DNA is to insert it into a plasmid with RE, use the plasmid
to transform a bacterial culture, grow a large number of modi-
fied bacteria, extract the DNA, and then clip it back out with the
appropriate RE.
Cells
For most uses, and particularly for use as a drug, a protein must be
consistent, so that every molecule in the bottle is just like every other
molecule. An important method used to increase the odds that every
protein in the bottle is identical is to make sure that the cells produc-
ing the protein—whether bacteria, animal, or human—are identical
with the gene cassette in the same place in the cell's genetic material.
The process of producing a culture of identical cells descended from
a single common ancestor is also called cloning. Whether the cells are
bacterial, yeast, plant, animal, or human, the principle of creating a
culture of genetically identical cells is the same: First, scientists need
the mixture of the cells with a known concentration and a little
plastic tray with a set of small wells, each able to hold about 1/100 th
of a liter. Then, the scientists will:
• dilute the mixture of cells so that when he or she delivers
a 1/100 th of liter to each well in a plastic culture plate, by
chance each well will receive no more than one cell; and
• provide the needed temperature and nutrients in the
culture wells so that each cell divides repeatedly.
Every cell in each resulting individual culture will be genetically
identical, though the cultures may be different from each other.
Then the scientists test a sample from each well to see which ones