An autosomal recessive gene is one which is required in two copies on an autosome to be active in an organism. For instance, a person who carry two copies of the same abnormal gene (in other words, this person is homozygous for the gene) will experience effects from that gene (for instance, he or she might then suffer from a disease coded by that gene). The gene can be inherited from both parents who carry the gene; sons and daughters have an equal chance of inheriting the gene. If a person has a genetic disease but his or her parents seem normal, then this probably means that: The parents of this person are heterozygous, unaffected carriers of the disease, or The person inherited one copy of the gene from a parent, and the other "good" copy underwent a mutation early in the person's embryonic development