In our family studies we compare the DNA (genetic material) inherited by family members who have a specific eye disorder to DNA from those in the family who did not inherit the disorder. By finding a common region of DNA between affected family members that is not shared with others in the family, we are able to identify a region of DNA that contains the gene for the disorder of interest. The analysis used to do these family studies is called linkage analysis and its strength relies heavily on the number of family participants. By studying very large families and/or many families with the same disorder, enough data can be analyzed to eventually pinpoint the gene responsible for the disorder.

Once a disease region has been localized to a chromosomal location, it is possible to identify the causative gene by screening sequences within that region. DNA is composed of four different types of substances known as nucleotides: A (Adenine), T (Thymine), G (Guanine) and C (Cytosine). By determining the nucleotide sequence in a gene in an individual affected with the disorder it is possible to determine whether they carry an altered sequence to available published information or if it remains the same. If a change is identified, then sequencing a subset of the population for this gene will determine whether the change in the normal gene sequence is a polymorphism (non disease causing) or pathogenic (disease causing). In order to corroborate the evidence that a disease gene has been identified it is important to find changes in several unrelated families.

Once a gene is identified, we can study the gene and its protein product. We examine if there are different mutations (changes) within a given gene and, if so, if their effects on gene function vary. We also examine at what time and in what tissues the gene is active, and what its protein product does. This information gives us insight into the gene's function and its role in the development of the brain and extraocular muscles.