| promorphology | <biology, study> Crystallography of organic forms; a division of morphology created by Haeckel. It is essentially stereometric, and relates to a mathematical conception of organic forms. See Tectology. (04 Mar 1998) |
|---|---|
| promoter | <molecular biology> A region of DNA to which RNA polymerase binds before initiating the transcription of DNA into RNA. The nucleotide at which transcription starts is designated +1 and nucleotides are numbered from this with negative numbers indicating upstream nucleotides and positive downstream nucleotides. most bacterial promoters contain two consensus sequences that seem to be essential for the binding of the polymerase. The first, the Pribnow box, is at about 10 and has the consensus sequence 5' TATAAT 3'. The second, the 35 sequence, is centred about 35 and has the consensus sequence 5' TTGACA 3'. most factors that regulate gene transcription do so by binding at or near the promoter and affecting the initiation of transcription. Much less is known about eukaryote promoters, each of the three RNA polymerases has a different promoter. RNA polymerase I recognises a single promoter for the precursor of rRNA. RNA polymerase II, that transcribes all genes coding for polypeptides, recognises many thousands of promoters. most have the Goldberg Hogness or TATA box that is centred around position 25 and has the consensus sequence 5' TATAAAA 3'. Several promoters have a CAAT box around 90 with the consensus sequence 5' GGCCAATCT 3'. There is increasing evidence that all promoters for housekeeping genes contain multiple copies of a GC rich element that includes the sequence 5' GGGCGG 3'. Transcription by polymerase II is also affected by more distant elements known as enhancers. RNA polymerase III synthesises 5s ribosomal RNA, all tRNAs and a number of small RNAs. The promoter for RNA polymerase III is located within the gene either as a single sequence, as in the 5s RNA gene or as two blocks, as in all tRNA genes. (13 Nov 1997) |
| promoter insertion | <molecular biology> Activation of a gene by the nearby integration of a virus. The long-terminal repeat acts as a promoter for the host gene. A form of insertional mutagenesis. (18 Nov 1997) |
| promoter regions | <genetics> DNA sequences which are recognised (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the pribnow box in bacteria and the tata box in eukaryotes. (12 Dec 1998) |
| promotion | Stimulation of tumour induction, following initiation, by a promoting agent which may of itself be noncarcinogenic. (05 Mar 2000) |
| prompt insulin zinc suspension | Sterile suspension of insulin in buffered water for injection, modified by the addition of zinc chloride such that the solid phase of the suspension is amorphous; it contains 40 or 80 units per ml; the duration of action is equivalent to that of insulin injection. Synonym: amorphous insulin zinc suspension, semilente insulin. (05 Mar 2000) |
| promuscis | <zoology> The proboscis of hemipterous insects. Origin: L, corruption of proboscis. Source: Websters Dictionary (01 Mar 1998) |
| promyelocyte | <haematology> Cell of the bone marrow that derive from myeloblasts and will give rise to myelocytes, precursors of myeloid cells and neutrophil granulocytes. (18 Nov 1997) |