What is an individual who has a recessive disease causing allele?

An individual with a recessive disease-causing allele carries one or two copies of the allele for the disease but may not exhibit symptoms if they have a dominant normal allele. If they have two recessive alleles, they will typically express the disease. Carriers, who possess one recessive allele and one normal allele, can pass the allele to their offspring, potentially leading to the disease in subsequent generations if both parents are carriers.