| lethal dose 50 | <pharmacology> The amount, or dosage, of a toxin necessary to kill 50% of the experimental subjects. (16 Mar 1998) |
|---|---|
| lethal equivalent | A combination of selective effects that on average have the same impact on the composition of the gene pool as one death; e.g., two carriers at 50% risk of dying would be the lethal equivalent of one carrier at 100% risk, in the population genetics of recessive traits lethal equivalent is expressed as twice the sum of the expected number of deaths ascribable to the genetic load. Expression used of the genetic load of recessive genes in heterozygous state that if in homozygous state would cause death or carry a risk of death. The expected number of deaths from all such genes is expressed in lethal equivalent. (05 Mar 2000) |
| lethal factor | A disorder that prevents effective reproduction by those affected; e.g., Klinefelter syndrome. (05 Mar 2000) |
| lethal gene | A gene that produces a genotype that leads to death of the organism before reproduction is possible or that precludes reproduction; for a recessive gene the homozygous or hemizygous state is lethal. (05 Mar 2000) |
| lethal midline granuloma | Destruction of the nasal septum, hard palate, lateral nasal walls, paranasal sinuses, skin of the face, orbit and nasopharynx by an inflammatory infiltrate with atypical lymphocytic and histiocytic cells; presumably a form of lymphoma in most cases. An obsolete term for polymorphic reticulosis. Synonym: granuloma gangrenescens, malignant granuloma, midline malignant reticulosis granuloma. (05 Mar 2000) |
| lethal mutation | <genetics, molecular biology> Mutation that eventually results in the death of an organism carrying the mutation. (18 Nov 1997) |
| achondroplastic dwarfism | See: achondroplasia. (05 Mar 2000) |
| acromelic dwarfism | A form of dwarfism in which shortening is striking in the most distal segment of the limbs; autosomal recessive inheritance. Synonym: acromelic dwarfism. Origin: acro-+ G. Melos, limb, + ia, condition (05 Mar 2000) |
| aortic dwarfism | Underdevelopment of physical stature associated with severe aortic stenosis. (05 Mar 2000) |
| asexual dwarfism | Dwarfism in which adult sexual development is deficient. (05 Mar 2000) |
| ateliotic dwarfism | A state in which the secretion of all anterior pituitary hormones is inadequate or absent; caused by a variety of disorders that result in destruction or loss of function of all or most of the anterior pituitary gland. Rare forms of PHP are inherited as autosomal recessive or as an X-linked recessive. Synonym: ateliotic dwarfism, hypophyseal cachexia, hypophysial cachexia. (05 Mar 2000) |
| camptomelic dwarfism | Dwarfism with shortening of the lower limbs due to anterior bending of the femur and tibia. (05 Mar 2000) |
| panhypopituitary dwarfism | Type I is an autosomal recessive disorder with deficient human growth hormone, ACTH, FSH, etc., having delayed sexual development, hypothyroidism, and adrenal insufficiency; type II is similar but is an X-linked disorder. (05 Mar 2000) |
| mesomelic dwarfism | Dwarfism with shortness of the forearms and lower legs. (05 Mar 2000) |
| metatropic dwarfism | Congenital disproportionate dwarfism in which the trunk is long relative to the limbs at birth but undergoes reversal of this proportion with subsequent development. (05 Mar 2000) |