Which gene the child receives from a parent is determined randomly. Just as when we flip a coin, whether it comes up heads or tails is a random event. Occasionally, something happens that causes a gene to change. Geneticists call this change a mutation. It is estimated that each of us have several mutated genes.
Most mutations have no effect on the individual, but some mutations cause disease.
In order to have Usher Syndrome, a person must have a mutation in both genes of the pair that can cause Usher Syndrome. However, this person will be a carrier of Usher Syndrome. It is estimated that about 1 in every 75 people carry an Usher gene, most do not know they carry the gene. If both of the mother and father are carriers, they could have children with Usher Syndrome. If the child receives the changed gene from each parent, that child will have a pair of changed genes.