• A Guide for Patients and Families

    ExomeSeq is a test that looks at most of the genes. This test may be useful for patients whose medical and family histories suggest a genetic cause for their signs and symptoms. Most patients who have whole exome sequencing (WES) have had other genetic testing that did not find a genetic cause of their condition.

    > Download a printable version of our Guide for Families.

  • Genetics Information

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    Genes are chemical instructions that tell a cell what job to perform. A gene is like a recipe for making a particular protein. Proteins do important jobs in every cell of the body.

    Genes are written in code, with four chemicals (represented by the letters A, T, C, and G) that spell out the instructions to make a protein. People generally have two copies of most genes, one copy from each parent.

    Genes make proteins.

    Most genes are made up of introns and exons. Exons are the parts of the gene that contain the information used to make a protein. They are the “coding” part of the gene. Introns are regions of DNA in between exons and do not code for proteins.

    Parts of a gene: Introns and exons

    Your DNA is your own personal blueprint for life. The genome includes a person’s entire DNA, both the introns and the exons. The exome includes only the exons (the parts used to make proteins). The introns and other non-coding sequences of DNA are not part of the exome. If you think of the genome as all of the action in a football game, the exome is like the game highlights with many of the important plays.

      Genome vs. Exome.

    There are several types of genetic tests. Some genetic tests “read” the genetic code of a single gene to see if that gene has any changes. Other genetic tests look for extra or missing pieces of DNA. Whole exome sequencing reads through the exons of most of the genes all at once.

    A mutation is a change in the DNA. Mutations may cause proteins to work poorly or to not be made at all. If you think of a gene as a recipe for making a protein, a mutation is like a mistake in the recipe that causes the protein to not work normally.

    Mutations may be “misspellings” where the wrong letter is included in the gene, or they may be deletions or duplications where there is missing or extra DNA in a gene. Genetic mutations are random. People cannot do anything to cause mutations or to stop them from happening.

    Genetic mutations: an error in the recipe.