fingerprinting. The use of DNA fingerprinting depends upon the presence of
repeating base sequences. These sequences are called restriction fragment length
polymorphosis, or the RFLP pattern, which is unique for every individual.
This is a sort of molecular signature or fingerprint. In order to perform DNA
fingerprinting, DNA must be taken from an individual. Samples can be taken
from hair, blood, skin, cheek cells, or other tissue. The DNA is taken from the
cells and is broken down with enzymes. The fragments are separated with elec-
trophoresis. The DNA fragments are then analyzed for RFLPs using DNA
probes. An evaluation enables crime lab scientists (forensic pathologists) to
compare a person’s DNA with the DNA taken from a scene of a crime. This tech-
nique has a 99 percent degree of certainty that a suspect was at a crime scene.
INDUSTRIAL APPLICATION: SHOW ME THE MONEY
Industrial applications of recombinant DNA technology include manufacturing
protein products by the use of bacteria, fungi, and cultured mammal cells. The
pharmaceutical industry is producing several medically important polypeptides
using biotechnology. An example is bacteria that metabolize petroleum and
other toxic materials. These bacteria are constructed by assembling catabolic
genes on a single plasmid and then transforming the appropriate organism.
Another example is vaccines. The hepatitis B vaccine is made up of viral protein
manufactured by yeast cells, which have been recombinedwith viral particles.
AGRICULTURAL APPLICATIONS: CROPS AND COWS
Recombinant DNA and biotechnology have been used to increase plant growth
by increasing the efficiency of the plant’s ability to fix nitrogen. Scientists take
genes for nitrogen fixation from bacteria and place the genes into plant cells.
Because of this, plants can obtain nitrogen directly from the atmosphere. The
plants can produce their own proteins without the need for bacteria. Another way
to insert genes into plants is with a recombinant tumor-inducing plasmid Ti plas-
mid. This is obtained from the bacterium Agrobacterium tumefaciens. This bac-
teria invades plant cells and its plasmids insert chromosomes that carry the genes
for tumor induction. An example of recombinant DNA with livestock is the
recombinant bovine growth hormone that has been used to increase milk pro-
duction in cows by 10 percent.
U.S. farmers grow substantial amounts of genetically modified crops. About
one-third of the corn and one-half of the soybean and cotton crops are genetically
CHAPTER 8 Recombinant DNA Technology^135