- A small rodent belonging to the genus Mus.- knockout m. a m. from whose genome a single gene has been artificially deleted.Experimental animals lacking specific genes have become valuable research tools in many branches of medicine, including genetics, physiology, pharmacology, immunology, cell biology, and oncology. A transgenic animal is one into whose genome a foreign gene, constructed by recombinant DNA technology, has been deliberately inserted. Placement of the inserted gene at a specific locus in the genome is made possible by incorporating it in a vector in which it is flanked by DNA sequences unique to the target site. The artificial genetic material is introduced into an embryo, which then develops into a chimera whose tissues contain both normal cells and cells containing the transgene. Matings among such animals yield some offspring that are homozygous for the transgene. If the inserted gene is a nonfunctional (null) allele, it deletes or “knocks out” the normal, wild allele. Not only is the deleted gene not expressed, but the offspring of matings among homozygous individuals constitute a pure strain, all of whose members lack the gene. Although theoretically any animal could be subjected to the knockout technique, mice have been used almost exclusively. Mice are small and easily maintained, and they reproduce rapidly and have a short life span. In addition, m. and human genomes are strikingly similar, with about 75% correspondence of genes. The fact that knockout mice lacking a wide variety of genes are often phenotypically normal indicates that the m. genome, like that of human beings, often has sufficient redundancy to compensate for a single missing pair of alleles. Knockout mice lacking the p53 tumor suppressor gene are used in studies of carcinogenesis, while those lacking the gene for the LDL receptor constitute an animal model of human familial hypercholesterolemia. Knockout mice have proved valuable in revealing the functions of genes for which mutant strains were not previously available.- New Zealand mice inbred strains of mice, either black (NZB) or white (NZW), unique among strains used in experimental immunology because of their proclivity to spontaneous immunologic abnormalities and disorders including systemic lupus erythematosus similar to that found in humans.- transgenic mice (tranz′jen-ik) Mice that have a piece of foreign DNA integrated into their genome.
* * *1) any of numerous small rodents with pointed snout, rather small ears, elongated body, and slender hairless or sparsely haired tail, including all the smaller members of the genus Mus (as the medically significant house mouse, M. musculus) and many members of other rodent genera and families having little more in common than their relatively small size2) a dark-colored swelling caused by a blow specif BLACK EYE
* * *(mous) 1. any of numerous small rodents of the family Muridae; some are household pests around the world and others are used as experimental animals. 2. a small weight, or movable structure.
Medical dictionary. 2011.