Molecular Pathology
The tools of molecular biology are contributing to the recent rapid growth of new tests with both greater accuracy and precision in many areas of laboratory medicine. Infectious agents can be identified by virtue of unique DNA sequences.
Molecular identification of chromosomal rearrangements is used not only in diagnosis, but also in monitoring for the effectiveness of therapy and detection of residual disease. Genetic alterations underlying heart diseases, iron metabolism defects, and congenital abnormalities, to name a few, are appreciated to be far more common than was previously recognized.
Prenatal screening is now available to detect hemoglobin disorders and many metabolic diseases, such as cystic fibrosis. Genetic susceptibility to inherited cancer is another dynamic new testing area. 
For example, the advent of new treatments for certain breast cancers depends on identification of a gene that is amplified and over-expressed in those cancers; the gene amplification can be identified by molecular testing. The metabolism of many important medications can also be predicted by molecular techniques.