Whole genome and exome sequencing

How scientists look for gene changes

DNA is organized into approximately 20,000 genes. Genes are packaged into chromosomes. A person usually has 23 pairs of chromosomes, or a total of 46 chromosomes. This entire collection of DNA is called your genome.

Genes that do not work correctly can cause disease. There are different ways to look at your DNA. Researchers often use a technology called sequencing to look at your DNA. Sequencing “reads” each letter of the DNA and finds changes (also called “variations” or “mutations”) in your genes that may cause disease or affect your risk for a disease.

Whole genome sequencing

Researchers can look closely at large amounts of genetic information by sequencing, or “reading,” every letter in your DNA (your genome). Sequencing of a person’s entire genetic code is called “whole genome sequencing.”

Exome sequencing

Surprisingly, most of your genome does not contain genes. There are many sections of DNA that do not contain any genes. Often, researchers will sequence only the parts of the genome that contain genes. These parts are called the “exome.”

The exome makes up about 1 percent of the genome, and gives the instructions to make all the proteins in your body. Sometimes the fastest way to look for changes that may cause disease is to look only at the exome. This is called “exome sequencing.”