| recognition factors | Factors which effect "recognition" of target antigens by polymorphonuclear leukocytes; apparently the Fc portion of antibody molecules and the activated third component of complement (C3), for both of which phagocytes have receptor sites. (05 Mar 2000) |
|---|---|
| recognition sequence | A nucleotide sequence --typically composed of 4, 6, or 8nucleotides -- that is recognised by a restriction endonuclease. Type II enzymes cut (and theircorresponding modification enzymes methylate) within or very near the recognition sequence. (09 Oct 1997) |
| recognition time | The interval between the application of a stimulus and the recognition of its nature. (05 Mar 2000) |
| pattern recognition | In information retrieval, machine-sensing or identification of visible patterns (shapes, forms, and configurations). (harrod's librarians' glossary, 7th ed) (12 Dec 1998) |
| pattern recognition, visual | Visually perceived characters, shapes, displays, or designs. (12 Dec 1998) |
| cell recognition | <cell biology> Interaction between cells that is possibly dependent upon specific adhesion. Since the mechanism is not entirely clear in most cases, the term should be used with caution. (26 Mar 1998) |
| signal recognition particle | A complex between a 7S RNA and six proteins. SRP binds to the nascent polypeptide chain of eukaryotic proteins with a signal sequence and halts further translation until the ribosome becomes associated with the rough endoplasmic reticulum. One of the SRP proteins (srp54) binds GTP and in association with 7SRNA and srp19 has GTPase activity. (18 Nov 1997) |
| signal recognition particle receptor | Receptor for the signal recognition particle (SRP) found in the membrane of the endoplasmic reticulum. Also called docking protein. Heterodimeric, both protomers having GTP binding capacity, though dissimilar binding sites. Not until the complex of SRP, ribosome, message and nascent polypeptide chain binds to the SRP receptor is the block to further chain elongation released and concurrently the SRP is released, leaving the ribosome attached to the endoplasmic reticulum membrane. Cotranslational transport of the polypeptide delivers it into the lumen of the ER. (18 Nov 1997) |
| dual recognition hypothesis | An outmoded hypothesis that is known to be incorrect now that the structure of the T-cell receptor is known. The proposal was that viral (and some chemical) antigens were recognised in association with histocompatibility antigens by separate receptors on the T-cell. The generation of cytotoxic T-cells was by association with Class I MHC antigens, of T helper cells by association with Class II MHC antigens. See: altered self hypothesis. (18 Nov 1997) |
| amber codon | <molecular biology> One of the three terminator codons. Its sequence is UAG. See: ochre codon, opal codon. (18 Nov 1997) |
| ambiguous codon | <molecular biology> A codon that codes for more than one amino acid. (09 Oct 1997) |
| codon | <molecular biology> The coding unit of DNA that specifies the function of the corresponding messenger RNA. A triplet of bases recognised by anticodons on transfer RNA and hence specifying an amino acid to be incorporated into a protein sequence. The code is degenerate, i.e. Each amino acid has more than one codon. The stop codon determines the end of a polypeptide. (18 Nov 1997) |
| codon, initiator | Any codon that directs initiation of genetic translation (translation, genetic) by stimulating the binding of initiator trna. In prokaryotes, the codons aug or gug can act as initiators while in eukaryotes, aug is the only initiator codon. (12 Dec 1998) |
| codon, nonsense | A codon that is not assigned to an amino acid or to any stop signal. It was originally thought that nonsense codons were synonymous with terminator codons (codon, terminator) in that they signaled termination of a protein chain. Recent studies have found this not to be true. (12 Dec 1998) |
| codon, terminator | Any codon that signals the termination of genetic translation (translation, genetic) by triggering the hydrolysis of the aminoacyl bond connecting the completed polypeptide to the trna. Terminator codons (uaa, uag, and uga) do not specify amino acids. (12 Dec 1998) |