Genetic diseases are known occur due to various types of mutations in the human genome. The molecular assays to diagnose these diseases have been developed based on the type of mutation commonly seen in each disease. Advances in the field molecular genetics have now made it possible to sequence whole exome or whole genome of an individual through next generation sequencing. Whole exome sequencing is already being used in clinical practice for diagnosis of rare disorders. It is now possible to sequence multiple genes responsible for a phenotype at much lower cost using these technologies. Hence the question arises whether the traditional methods based on capillary electrophoresis are still relevant or not? And the answer is a big YES. Although next generation sequencing can provide an answer in most of the cases, there are certain situations in molecular diagnostics where Sanger sequencing can provide efficient and cost effective solutions. Diseases showing genetic homogeneity for mutations, like sickle cell anemia, achondroplasia etc, common mutations in populations and those caused due of mutations in single genes of small size, e.g Beta thalassemia, are better tested using sanger sequencing of specific exons.
Sanger sequencing is very important for familial segregation study, prenatal diagnosis and family screening following identification of a variant in next generation sequencing based assay. Fragment analysis following fluorescent primer based PCR is very helpful in initial screening of patients with Duchenne muscular dystrophy or Spinal muscular atrophy, wherein the common genetic mechanism is a deletion/duplication of one or several exon/s. Triplet repeat disorder testing for diseases like Spinocerebellar ataxias, Fragile X syndrome etc, relies heavily on capillary electrophoresis for detection of repeat expansion. Various examples of relevance of capillary electrophoresis in today’s era of molecular diagnosis of genetic diseases will be discussed in the presentation.