| ILC | ichthyosis linearis circumflex; incipient lethal concentration |
|---|---|
| LA50 | total body surface area of burn that will kill 50% of patients (lethal area) |
| LC | Laennec cirrhosis; Langerhans cell; late clamped; large chromophobe; lecithin cholesterol acyltransf... |
| LC50 | median lethal concentration |
| LCSS | lethal congenital contracture syndrome |
| somatic mutation | Mutation that occurs in the somatic tissues of an organism and that will not, therefore, be heritable, since it is not present in the germ line. Some neoplasia is due to somatic mutation, a more conspicuous example is the reversion of some branches of variegated shrubs to the wild type (completely green) phenotype. Somatic mutation is probably also important in generating diversity in V gene regions of immunoglobulins. (18 Nov 1997) |
|---|---|
| somatic mutation theory of cancer | That cancer is caused by a mutation or mutations in the body cells (as opposed to germ cells), especially nonlethal mutations associated with increased proliferation of the mutant cells. (05 Mar 2000) |
| spontaneous mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| neutral mutation | A mutation that has no selective advantage or disadvantage. Considerable controversy surrounds the question of whether such mutations can exist. (18 Nov 1997) |
| new mutation | Redundant term for a heritable trait present in the offspring but in neither parent, i.e., not a pre-existing mutant form inherited. (05 Mar 2000) |
| substitution mutation | A mutation caused by a nucleotide base being replaced by a different one. (09 Oct 1997) |
| nonsense mutation | <molecular biology> A mutation that causes a polypeptide chain to be ended prematurely. (13 Nov 1997) |
| null mutation | Change in a gene that leads to nothing, for example to no enzyme or to a nonfunctioning enzyme. (12 Dec 1998) |
| suppressor mutation | <molecular biology> Mutation that alleviates the effect of a primary mutation at a different locus. May be through almost any mechanism that can give a primary mutation, but perhaps the most interesting class are the amber and ochre supressors, where the anticodon of the tRNA is altered so that it mis reads the termination codon and inserts an amino acid, preventing premature termination of the peptide chain. (18 Nov 1997) |
| deletion mutation | <molecular biology> A mutation in which one or more (sequential) nucleotides is lost by the genome. If the number lost is not divisible by 3 and is in a coding region, the result is a frameshift mutation. (18 Nov 1997) |
| down promoter mutation | <molecular biology> A mutation (a change in base pair sequence) in a promoter region, this results in lower gene expression (less transcription of the gene occurs). (09 Oct 1997) |
| induced mutation | A mutation caused by exposure to a mutagen. (05 Mar 2000) |
| insertion mutation | A mutation caused by the insertion of at least one extra nucleotide basein a DNA sequence. (09 Oct 1997) |
| ochre mutation | Mutation that changes any codon to the termination codon UAA. (18 Nov 1997) |