A healthy person can still transmit a genetic disorder. A carrier possesses one copy of a recessive disease-causing allele yet does not show the associated phenotype. The second, functional allele produces enough of the needed protein to maintain normal function.

Carriers of cystic fibrosis, Tay-Sachs, or sickle cell alleles are usually asymptomatic. When two carriers reproduce, each pregnancy carries a 25 percent risk of an affected child. Population screening programs identify carriers so that couples can make informed reproductive choices.

Molecular tests detect specific pathogenic variants. Family history alone is often incomplete because carriers remain healthy. Expanded carrier screening panels now examine dozens or hundreds of recessive conditions in a single assay, improving detection rates across diverse ancestries.

• Individual with one recessive disease allele
• Typically shows no clinical symptoms
• Can transmit the allele to offspring
• Identified through genetic testing