| RE | radium emanation; readmission; rectal examination; reference emitter; reflux esophagitis; regional e... |
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| RELP | restriction fragment length polymorphism |
| RELV | restriction fragment length variant |
| RFLP | restriction fragment length polymorphism |
| MHC restriction | <immunology> Restriction on interaction between cells of the immune system because of the requirement to recognise foreign antigen is association with MHC antigens (major histocompatibility antigens). Thus, cytotoxic T-cells will only kill virally infected cells that have the same Class I antigens as themselves, whereas helper T-cells respond to foreign antigen associated with Class II antigens. (18 Nov 1997) |
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| host restriction-modification | A bacterial system where the bacterium is able to destroy invading DNA from a bacteriophage (virus which infects bacteria) while at the same time preventing the destruction of their own DNA. The phage DNA is cleaved by a restriction enzyme made by the bacterium, the bacterial DNA is modified (usually with methylation) so that the enzyme will not destroy it. (09 Oct 1997) |
| DNA restriction enzymes | <enzyme> Enzymes that are part of the restriction-modification systems. They catalyze the endonucleolytic cleavage of DNA sequences which lack the species-specific methylation pattern in the host cell's DNA. Cleavage yields random or specific double-stranded fragments with terminal 5'-phosphates. The function of restriction enzymes is to destroy any foreign DNA that invades the host cell. most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. They are also used as tools for the systematic dissection and mapping of chromosomes, in the determination of base sequences of dnas, and have made it possible to splice and recombine genes from one organism into the genome of another. Registry number: EC 3.1.21 (12 Dec 1998) |
| DNA restriction-modification enzymes | Systems consisting of two enzymes, a modification methylase and a restriction endonuclease. They are closely related in their specificity and protect the DNA of a given bacterial species. The methylase adds methyl groups to adenine or cytosine residues in the same target sequence that constitutes the restriction enzyme binding site. The methylation renders the target site resistant to restriction, thereby protecting DNA against cleavage. (12 Dec 1998) |
| ecori restriction enzyme | <enzyme, molecular biology> A commonly-used restriction enzyme (enzyme which will cleave the phosphodiester bonds of DNA at specific nucleotide sequences) that came from the bacteria Escherichia coli and recognises the sequence GAATTC. The enzyme will make a staggered cut of the double-stranded DNA molecule by cutting between the G and A on both strands. (09 Oct 1997) |
| lactase restriction | An inherited trait in which there is low lactase activity and thus there is defective lactose intestinal metabolism. Compare: lactase persistence. (05 Mar 2000) |
| active mutant | A mutant with overt phenotypic expression. (05 Mar 2000) |
| amber mutant | A mutant with a mutation resulting in a UAG codon. (05 Mar 2000) |
| auxotrophic mutant | Mutant with a nutritional requirement not present in the wild type organism. Synonym: defective organism, deficiency mutant. (05 Mar 2000) |
| gap mutant | <molecular biology> A fruit fly of the genus Drosophila which is missing a number of adjacent segments because the segments failed to develop. (09 Oct 1997) |
| rats, mutant strains | Rats bearing mutant genes which are phenotypically expressed in the animals. (12 Dec 1998) |
| virulent phage mutant | A mutant of a phage that is unable to establish lysogeny. (05 Mar 2000) |
| relaxed mutant | A mutant bacterium that continues to synthesise RNA in a medium that lackscertain nutrients or amino acids which that sort of bacterium normallyneeds present before it can make RNA. (09 Oct 1997) |
| ced mutant | <organism> Giant multinucleate fresh water amoeba (up to 5mm long) much used for studies on the mechanism of cell locomotion. (18 Nov 1997) |
| cell division cycle mutant | A yeast cell which has cell division cycle genes that have mutated to become sensitive to temperature, at certain temperatures (usually high ones), various parts of the normal yeast cell cycle become abnormal, and in some strains the yeast cell does not survive at all. (09 Oct 1997) |