| lethal dwarfism | Dwarfism leading to intrauterine or neonatal death. (05 Mar 2000) |
|---|---|
| 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) |
| active mutant | A mutant with overt phenotypic expression. (05 Mar 2000) |
| amber mutant | A mutant with a mutation resulting in a UAG codon. (05 Mar 2000) |
| auxotrophic mutant | Mutant with a nutritional requirement not present in the wild type organism. Synonym: defective organism, deficiency mutant. (05 Mar 2000) |
| gap mutant | <molecular biology> A fruit fly of the genus Drosophila which is missing a number of adjacent segments because the segments failed to develop. (09 Oct 1997) |
| rats, mutant strains | Rats bearing mutant genes which are phenotypically expressed in the animals. (12 Dec 1998) |
| virulent phage mutant | A mutant of a phage that is unable to establish lysogeny. (05 Mar 2000) |
| relaxed mutant | A mutant bacterium that continues to synthesise RNA in a medium that lackscertain nutrients or amino acids which that sort of bacterium normallyneeds present before it can make RNA. (09 Oct 1997) |
| ced mutant | <organism> Giant multinucleate fresh water amoeba (up to 5mm long) much used for studies on the mechanism of cell locomotion. (18 Nov 1997) |
| cell division cycle mutant | A yeast cell which has cell division cycle genes that have mutated to become sensitive to temperature, at certain temperatures (usually high ones), various parts of the normal yeast cell cycle become abnormal, and in some strains the yeast cell does not survive at all. (09 Oct 1997) |