Lab Tests Using Recombinant Components - Biotechnology and Your Health: Pharmaceutical Applications - page 141

unwarranted invasion of privacy. Another practice that disturbs some
people is when law enforcement agencies keep convicts' DNA samples
for later analysis. The situation is further clouded by laws passed in
Louisiana and Texas that require DNA samples from people arrested
for certain offenses, even if DNA analysis is not required for the
prosecution of the offense. As with the introduction of any new
technology in law enforcement, these issues will likely wind their
way through the state and federal courts over the coming years.
The Use of DNA Microarray
The way a cell or tissue looks under a microscope can provide use-
ful information in diagnosing disease or in choosing an appropriate
treatment for an illness. New methods that provide a detailed
accounting of what genes are being read to produce proteins in a
tissue sample also may provide important information to a doctor.
These tests, using devices called DNA microarray or gene chips , have
become important laboratory research tools and are beginning to be
applied to medical care (Figure 10.2).
The tests are based on information gained from the human
genome project and computer chip manufacturing technology. The
messenger RNA copy of a gene used to make a protein in a cell is
complementary to and will bind to the DNA gene. To find out
which genes are being used, the cell's RNA is copied into fluorescent
dye-tagged DNA using PCR with a collection of fluorescent-dye-
linked primers for a large number of genes. A robotic machine
deposits a defined array of small amounts of all the different genes
to be tested onto a piece of glass or nylon. If the PCR products bind
to a spot on the chip, that spot—the particular gene—will become
fluorescent. The chip is then analyzed to provide a list of the genes
that the cell is using to make proteins.
Scientists have developed a DNA microarray test that predicts
whether a woman with a certain type of breast cancer will have the
cancer recur after the tumor is removed. This helps physicians and