Genetic A genetic disorder is a disease caused by problems in someone's DNA. A disorder can be from just a single gene or an entire chromosome. Most disorders are quite rare and affect one in every thousand people. Genetic mutations are mostly caused by genes that are passed down by their parents. Depending on the type of disorder a person can have recessive or dominant genes to a particular disease. For example, Person A has a gene for Autism whereas person B doesn't. If the child has a recessive gene towards the Autism, he/she would not carry it. If the gene is dominant then the child will carry it.
Environment While some disorders or mutations are genetic.....it can also be caused by the environment. A good example of environmental mutations -disorders can be the exposure to radiation or smoking. Other causes from the environment can include .....cosmic rays,tobacco and even some viruses.