Exome sequencing (also known as Whole Exome Sequencing or WES) is a technique for sequencing all the protein-coding genes in a genome (known as the exome). It consists of first selecting only the subset of DNA that encodes proteins (known as exons), and then sequencing that DNA using any high throughput DNA sequencing technology. There are 180,000 exons, which constitute about 1% of the human genome, or approximately 30 million base pairs. The goal of this approach is to identify genetic variation that is responsible for both Mendelian and common diseases such as Miller syndrome and Alzheimer's disease without the high costs associated with whole-genome sequencing.