If the mother is the only carrier of the defective gene, there is a 50 % chance of passing the affected gene on to male children (in which case they would develop symptoms in adulthood). The chance of passing the defective gene to female children is also 50% (in which case they would be carriers of the gene, but usually would not ever develop actual symptoms).
If the father is the only carrier of the defective gene the chances of passing the defective gene to a male child are 0%. However, it is 100% certain that the defective gene will be passed on to a female child, and she will be a carrier of the gene.
Note: Females are usually ONLY carriers. However, it is not unheard of for females to develop symptoms as well, although, these symptoms are usually not as severe as in males.