| addition mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
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| addition-deletion mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
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| addition | 1. The act of adding two or more things together; opposed to subtraction or diminution. "This endless addition or addibility of numbers." 2. Anything added; increase; augmentation; as, a piazza is an addition to a building. 3. <mathematics> That part of arithmetic which treats of adding numbers. 4. A dot at the right side of a note as an indication that its sound is to be lengthened one half. 5. A title annexed to a man's name, to identify him more precisely; as, John Doe, Esq.; Richard Roe, Gent.; Robert Dale, Mason; Thomas Way, of new York; a mark of distinction; a title. 6. Something added to a coat of arms, as a mark of honor; opposed to abatement. <geometry> Vector addition, that kind of addition of two lines, or vectors, AB and BC, by which their sum is regarded as the line, or vector, AC. Synonym: Increase, accession, augmentation, appendage, adjunct. Origin: F. Addition, L. Additio, fr. Addere to add. Source: Websters Dictionary (01 Mar 1998) |
| addition compound | Strictly, a complex of two or more complete molecules in which each preserves its fundamental structure and no covalent bonds are made or broken (e.g., hydrates of salts, adducts), loosely, association of acids with basic organic compound's (e.g., amines with HCl), more loosely, addition of two molecules without loss of any atom, but forming new covalent bonds (e.g., CH2==CH2 + Br2 → BrCH2-CH2Br). (05 Mar 2000) |
| addition polymer | <chemistry> A polymer which is formed from the fusion of two monomers which join completely without losing any small molecules. (15 Jan 1998) |
| addition reaction | <chemistry> Any reaction in which two chemicals combine to form a single chemical. (15 Jan 1998) |
| terminal addition enzyme | <enzyme> A non-template-directed DNA polymerase normally found in vertebrate thymus and bone marrow. It catalyses the elongation of oligo- or polydeoxynucleotide chains and is widely used as a tool in the differential diagnosis of acute leukaemias in man. Chemical name: Nucleoside-triphosphate:DNA deoxynucleotidylexotransferase Registry number: EC 2.7.7.31 (12 Dec 1998) |
| acquired mutation | A change in a gene or chromosome that occurs in a single cell after the conception of the individual. That change is then passed along to all cells descended from that cell. Acquired mutations are involved in the development of cancer. (12 Dec 1998) |
| amber mutation | <molecular biology> A mutation from a codon which codes for an amino acid into the amber codon UAG, which normally signals that the translation of mRNA into an amino acid chain should stop. The mutation causes the amino acid chain to stop forming before it is actually completed. (09 Oct 1997) |
| back mutation | <molecular biology> A mutation that causes a mutant gene to revert to its original wild-type base sequence. Compare: forward mutation. (09 Oct 1997) |
| reading-frameshift mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
| germinal mutation | A mutation in the germ cells (the cells which will undergo meiosis to form the gametes). Such mutations are therefore passed on to offspring. (09 Oct 1997) |
| germ-line mutation | Any detectable and heritable alteration in the lineage of germ cells. Mutations in these cells (i.e., "generative" cells ancestral to the gametes) are transmitted to progeny while those in somatic cells are not. (12 Dec 1998) |
| reverse mutation | <molecular biology> A mutation that causes a mutant gene to revert to its original wild-type base sequence. Compare: forward mutation. (09 Oct 1997) |
| chromosomal mutation | Can refer to any of a number of DNA mutations which results in a change in the protein encoded by the mutated gene, such as point mutations, insertion or deletion mutations (frameshift mutations), or nonsense mutations. More often this refers to mutations involving chromosomes, such as the inversion of part of one chromosome such that the inverted part no longer matches with its homologous pair, a translocation of one part of a chromosome to a different chromosome, deletions of parts of chromosomes, or accidents which happen during the division of the nucleus like the unequal portioning of chromosomes between the daughter cells. (09 Oct 1997) |
| missense mutation | <molecular biology> A mutation that alters a codon for a particular amino acid to one specifying a different amino acid. (18 Nov 1997) |