| mice, knockout | Mice whose genome contains a gene whose function has been disrupted, or "knocked-out". A common method of producing disabled genes using recombinant DNA technology is by inserting an antibiotic resistance gene into the normal DNA sequence of a clone of the gene being studied. This disrupts the gene's action, thereby preventing it from making an active protein product. Cells in which this transfer is successful are then injected into mouse embryos, producing chimeric mice. These mice are bred to yield a strain in which all the cells contain the knocked-out gene. Knockout mice are used as animal models for various diseases, such as cystic fibrosis, and are helping to clarify the functions of the genes studied within the fields of immunology, cancer genetics, and developmental biology. (12 Dec 1998) |
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| mice, mutant strains | Mice bearing mutant genes which are phenotypically expressed in the animals. (12 Dec 1998) |
| mice, neurologic mutants | Mice which carry mutant genes for neurologic defects or abnormalities. (12 Dec 1998) |
| mice, nude | Mutant mice homozygous for the recessive gene "nude" which fail to develop a thymus. They are useful in tumour studies and studies on immune responses. (12 Dec 1998) |
| mice, obese | Mutant mice exhibiting a marked obesity coupled with overeating, hyperglycaemia, hyperinsulinaemia, marked insulin resistance, and infertility when in a homozygous state. They may be inbred or hybrid. (12 Dec 1998) |
| mice, quaking | Mice homozygous for the mutant autosomal recessive gene, quaking (qk), associated with disorder in myelin formation and manifested by axial tremors. (12 Dec 1998) |
| mice, scid | Mice homozygous for the mutant autosomal recessive gene "scid" which is located on the centromeric end of chromosome 16. These mice lack mature, functional lymphocytes and are thus highly susceptible to lethal opportunistic infections if not chronically treated with antibiotics. The lack of b- and T-cell immunity resembles severe combined immunodeficiency (scid) syndrome in human infants. Scid mice are useful as animal models since they are receptive to implantation of a human immune system producing scid-human (scid-hu) haematochimeric mice. (12 Dec 1998) |
| mice, transgenic | Laboratory mice that have been produced from a genetically manipulated egg or embryo. The technique involves microinjection of foreign DNA fragments into the nucleus of the fertilised egg and transferring it into the uterus of a foster mother mouse. The inserted gene becomes integrated into every cell and tissue of the developing mouse, including its germ line cells. (12 Dec 1998) |
| micella | Origin: NL, dim. Of L. Mica a morsel, grain. <biology> A theoretical aggregation of molecules constituting a structural particle of protoplasm, capable of increase or diminution without change in chemical nature. Source: Websters Dictionary (01 Mar 1998) |
| micellar | Having the properties of an assemblage of micelles, i.e., of a gel. (05 Mar 2000) |
| micelle | 1. <biochemistry> A globule of lipid molecules in water where their nonpolar ends face inward and their polar tails face outward. 2. <chemistry> A colloid particle formed by an aggregation of small molecules. (12 Jan 1998) |
| micelles | Electrically charged colloidal particles or ions consisting of oriented molecules; aggregates of a number of molecules held loosely together by secondary bonds. (12 Dec 1998) |
| Michaelis complex | Binary complex of an enzyme. (05 Mar 2000) |
| Michaelis constant | <chemistry> The true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction (usually symbolised by Ks), the concentration of the substrate at which half the true maximum velocity of an enzyme-catalyzed reaction is achieved (when velocities are measured under initial rate and steady state conditions). The ratio of rate constants (k2 + k3)/k1 in the single-substrate enzyme-catalyzed reaction: E + S &dblarr; ES &dblarr; E + products where E represents the free enzyme, S is the substrate, and ES is the central binary complex. The expression for the Michaelis constant will be more complex for multisubstrate reactions. An apparent Michaelis constant is a constant determined either under conditions that are not strictly steady state and initial rate or one that varies with the concentration of one or more cosubstrates. See: Michaelis-Menten equation. Synonym: Michaelis-Menten constant. (05 Mar 2000) |
| Michaelis, Leonor | <person> German-U.S. Chemist, 1875-1949. See: Michaelis-Gutmann body, Michaelis constant, Michaelis-Menten constant, Michaelis-Menten equation, Michaelis-Menten hypothesis. (05 Mar 2000) |