2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part III: Genetics
Chapter 5: Molecular Genetics
The Search for Genes in Specific Diseases
A variety of methods have been used to assign individual genes to specific chromosomes, to link individual genes to one another, and to link diseases to specific genes.
Polymerase Chain Reaction
Polymerase chain reaction (PCR) is a technique used in molecular biology to amplify a single copy or a few copies of a segment of DNA or RNA by several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. PCR is a common and indispensable technique used in clinical and research laboratories for a broad variety of applications. Clinically, PCR has been utilized in establishing the etiology of ocular infections. For example, PCR performed on ocular fluids can detect numerous members of the herpes virus family.
PCR methods rely on thermal cycling, which involves exposing the reactants to repeated cycles of heating and cooling, permitting different temperature-dependent reactions of DNA melting and enzyme-driven DNA replication. Primers (short DNA fragments) containing sequences complementary to the target region, along with a DNA polymerase (usually Taq polymerase), enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the original DNA template is exponentially amplified.
Sugita S, Ogawa M, Shimizu N, et al. Use of a comprehensive polymerase chain reaction system for diagnosis of ocular infectious diseases. Ophthalmology. 2013;120(9):1761–1768.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.