lethal allele, an allele that produces a phenotypic effect that causes the death of the organism at any stage of life. The allele may be dominant, incompletely dominant, or recessive. Human diseases caused by lethal genes include Huntington’s disease, which is transmitted as an autosomal-dominant trait, and sickle cell anemia, which shows recessive lethality. Compare sublethal allele. See also lethal equivalent.
