US is inherited or passed from parents to their children through genes. Genes are located in every cell of the body and contain the instructions that tell cells what to do. Some genes specify traits such as hair color. Other genes are involved in the development of body parts, such as the ear. Still others determine how parts of the body work. Each person inherits two copies of each gene; one gene comes from each parent. Sometimes genes are altered or mutated. Mutated genes may cause cells to act differently than expected.
US is passed along in families by autosomal recessive inheritance, which requires two copies of the US gene before the disorder is seen. Each parent of a child with US usually has one standard and one mutated US gene. A child with US receives two mutated genes, one from each parent. Usually parents are unaware that they have or carry a US gene. This is because they would need two of the mutated genes in order to have signs of US. Presently, at least eight different genes are thought to cause the various types of US.
Original address of this page:
www.nih.gov/nidcd/health/pubs_hb/usher.htm#causes
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