| UA | absorption unsharpness; ultra-audible; ultrasonic arteriography; umbilical artery; unauthorized abse... |
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| UAP | unlicensed assistive personnel; unstable angina pectoris; urinary acid phosphatase; urinary alkaline... |
| UHD | unstable hemoglobin disease |
| 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) |
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| 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) |
| conditional mutation | <molecular biology> A mutation that is only expressed under certain environmental conditions for example temperature sensitive mutants. (05 Jan 1998) |
| point mutation | <molecular biology> Mutation that causes the replacement of a single base pair with another pair. (18 Nov 1997) |
| polar mutation | <molecular biology> A mutation in a single gene which affects the rate of expression of other genes that are near it on a chromosome. (09 Oct 1997) |
| mutation | 1. A change in form, quality or some other characteristic. 2. <genetics> A permanent transmissible change in the genetic material, usually in a single gene. Also, an individual exhibiting such a change. Also called (in classical genetics) a sport. Origin: L. Mutatio from mutare = to change (18 Nov 1997) |
| mutation rate | The frequency with which a particular mutation appears in a population or the frequency with which any mutation appears in the whole genome of a population. Normally the context makes the precise use clear. See: fluctuation analysis. (18 Nov 1997) |
| private mutation | A rare mutation found usually only in a single family or a small population. It is like a privately printed book. (12 Dec 1998) |
| hereditary mutation | A gene change that occurs in a germ cell (an egg or sperm) to become incorporated in every cell in the body. Hereditary mutations (also called germline mutations) play a role in cancer as, for example, the eye tumour retinoblastoma and wilms' tumour of the kidney. (12 Dec 1998) |
| homeotic mutation | <embryology, genetics> A mutation that causes an organism to develop a homologous body part or structure in place of the part or structure that should normally be there (for example, developing a hand in place of a foot). (09 Oct 1997) |
| silent mutation | Mutations that have no effect on phenotype because they do not affect the activity of the product of the gene, usually because of codon ambiguity. (18 Nov 1997) |