Each gene has two copies, one inherited from the father and the other from the mother. Being a carrier of a mutation means that the person has a change in one of the copies of a particular gene.
What are genes?
Each one of our cells contains genetic information, or DNA, organized into basic units, genes. Those that don’t function correctly are the ones responsible for genetic disorders.
The changes in the genes are called mutations, and we all carry a variable number of them.
Although carriers are healthy people, if both parents have a mutation in the same gene the probability of having a sick child is 25%