Genetics is the most recent discipline to emerge in pathology. The revolution in genetics, and our knowledge of genetic disorders, has been precipitated by the very rapid advances which have occurred in recombinant DNA (rDNA) technology, which allows the sequencing of the genetic make up of individuals.
There are two main branches of laboratory genetics:
- Clinical cytogenetics, which involves the microscopic analysis of chromosomal abnormalities, such as an increase or reduction in the number of chromosomes or a translocation of part of one chromosome to another. These techniques are used to diagnose such conditions as Downs Syndrome.
- Molecular genetics, which uses the tools of DNA technology to analyse mutations (changes) in genes. Many genes have been identified that are associated with such diseases as cystic fibrosis, breast cancer and diabetes mellitus.
The simple concept that genetic disorders involve single gene defects is changing, with more complex modes of genetic inheritance including polygenic, multifactorial (genes interacting with the environment), unstable DNA and epigenetic mechanisms (eg. imprinting), being described. As the Human Genome Project reaches its conclusion in the next few years, the number of human genes isolated will require the laboratory geneticist to keep up with new knowledge on a daily basis.
Pathologists involved in Genetics also play an important part in the "molecular medicine" team. This team provides patients with genetic problems, and their families, specialised advice from a range of health professionals including clinicians, counsellors, and the pathologist. The Pathologist is an essential team member because of his/her expertise in interpreting the results of laboratory genetic tests.