individual who has a recessive, disease-causing allele at a particular locus
on one chromosome of a pair and a normal allele at that locus on the other
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
A carrier is an individual who carries and is capable of passing on a genetic mutation associated with a disease and may or may not display disease symptoms. Carriers are associated with diseases inherited as recessive traits. In order to have the disease, an individual must have inherited mutated alleles from both parents. An individual having one normal allele and one mutated allele does not have the disease. Two carriers may produce children with the disease.