1. in in vitro fertilization, the choosing of one embryo over others because it is assessed as having a higher likelihood of developing into a healthy, viable fetus.

2. the choosing of traits for future progeny through genetic analysis and manipulation. Preselection of traits—for example, sex (see sex preselection), intelligence, beauty, and various talents—is highly controversial, with the potential for preselecting designer children raising serious ethical considerations.

3. a family’s subjective assignment of the role of mutation carrier to one or more family members prior to knowledge of their actual genetic status. Family members often treat the preselected person in a special way, assuming that he or she is a mutation carrier.