Carrier = an organism that has inherited a genetic trait or mutation, but displays no symptoms X-linked traits = traits that are passed on from parents to offspring on the X chromosome (the chromosome related to gender). Example is colorblindness. Dominance = a relationship between alleles of a single gene, in which one allele masks the phenotypic expression of another allele. Recessive = an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Allele is masked by dominant allele.