Biomedical Engineering Reference
In-Depth Information
Southern blot or
genomic DNA
Northern blot or
isolated mRNA
B mRNA
A
AAAAA
Cut with restriction enzyme;
separate fragments by Gel
electrophoresis
Separate mRNA by
size on denaturing gel
Larger
fragments
Fragments
containing A
Position of
B mRNA
Smaller
fragments
Transfer fragments to
nirtrocellulose filter
Hybridize with radio labeled
probe for a or b
Place aganist
X-ray film
Northern blot:
The position of the Band
indicates the size of mRNA;
Intensity indicates
its abundance
Southern blot:
The position of the
probe indicates the
size of restriction
fragment with the
hybridized sequence
7. 5
Northern and southern blotting to detect point mutations. This
fi gure illustrates the various steps that are taken to identify pieces of
genomic DNA via southern blots and mRNA sequences via northern
blots. Note the similar and distinct steps seen in each procedure.
(Image created by Edward Rodriquez, St Peter's University, Art
Department, Graphic Arts, Jersey City, NJ.)
the population because of the resistance to malaria that is conferred on
heterozygotes, who also have enough normal RBCs so the symptoms of
sickle cell anemia are not present.
It should be noted that not all mutations are found in germ cells. Mutations
can also be found in somatic cells, because of exposure to physical agents
or chemical mutagens present in the environment. These acquired somatic
mutations can accumulate over time and they are responsible for the ini-
tial genetic events seen in many tumors. The cause and effect relationship
of asbestos exposure to mesothelioma and of excessive ultraviolet radia-
tion exposure to the development of skin cancer are just two well-known
examples. A great deal of current cancer and molecular genetic research is
aimed at a better understanding and characterization of such relationships.
