Genetic Considerations in Oculoplastic Disorders

In this chapter we describe some basic genetic principles in the context of oculoplastic disease. We will review genetics starting from chromosome to protein. We will review the interaction between genes and environment and their involvement together in disease or presentation. We will discuss the relationship between gene and phenotype. We will discuss that not all genetic disorders penetrate each generation, a phenomenon called incomplete penetrance. We will discuss how the same condition in a single family can present with a range of symptoms, a lesson called variable expressivity. We will also review the basic anatomy of the human genome. The bulk of the chapter will then focus on recognizable patterns of inheritance. There are illustrations for quick reference to demonstrate each inheritance type. Each illustration includes a diagram including male and female figurines as well as the more classic Punnett squares. These illustrations will help those unfamiliar with genetics grasp the concepts without detailed reading or further exploration. We also review the different types of genetic testing which are chromosomal- and sequence-based tests. We hope these guidelines will allow appropriate test ordering by the oculoplastic physician.