Most sex-linked (X-linked) conditions are recessive. This means that in a person with two X-chromosomes (females), both copies of a gene (i.e., one on each X-chromosome), must have a change or mutation whereas in a person with one X-chromosomes (males), only one copy of a gene must have a mutation. A female with a mutation in one copy of a gene on the X-chromosome is said to be a 'carrier' for an X-linked condition. For X-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the X -chromosome can transmit either the X-chromosome with this mutation or a normal X-chromosome to her children. Autosomal dominant inheritance refers to the pattern of inheritance of a condition directly or indirectly due to a dominant faulty gene located on autosome. Autosomal recessive inheritance is the condition caused directly or indirectly due to a recessive faulty gene copy on autosome. Sex-linked dominant is a rare trait that is caused by a single abnormal gene on the X-chromosome.