| PPG | photoplethysmography; platelet proteoglycan; portal pressure gradient |
|---|---|
| PSG | peak systolic gradient; phosphate, saline, and glucose; polysomnogram; presystolic gallop; pregnancy... |
| PVG | pulmonary valve gradient |
| SDG | sucrose density gradient |
| THUG | thyroid uptake gradient |
| DNA sequence, unstable | DNA region comprised of a variable number of repetitive, contiguous trinucleotide sequences. Presence of these regions is associated with diseases such as fragile x syndrome and myotonia atrophica. (12 Dec 1998) |
|---|---|
| insertion sequence | Mobile nucleotide sequences that occur naturally in the genomes of bacterial populations. When inserted into bacterial DNA, they inactivate the gene concerned, when they are removed the gene regains its activity. Closely related to transposons and range in size from a few hundred to a few thousand bases, but are usually less than 1500 bases. (18 Nov 1997) |
| intervening sequence | <molecular biology> Alternative but uncommon name for an intron. (18 Nov 1997) |
| tandem repeat sequence | <molecular biology> Multiple copies of the same base sequence on a chromosome, used as a marker in physical mapping. (09 Oct 1997) |
| termination sequence | <molecular biology> The three codons, UAA known as ochre, UAG as amber and UGA as opal, that do not code for an amino acid but act as signals for the termination of protein synthesis. They are not represented by any tRNA and termination is catalysed by protein release factors. There are two release factors in E. Coli, RF1 recognises UAA and UAG, RF2 recognises UAA and UGA. Eukaryotes have a single GTP requiring factor, eRF. See: ochre suppressor, amber suppressor. (13 Jan 1998) |
| enhancer sequence | <molecular biology> A nucleotide sequence, located as many as several thousand base pairs away in either direction from the target gene, which enhances transcription of that gene. (14 Nov 1997) |
| evolutionarily conserved sequence | A base sequence in a DNA molecule (or an amino acid sequence in a protein) that has remained essentially unchanged throughout evolution. (12 Dec 1998) |
| Expressed Sequence Tag | <molecular biology> Expressed sequence tags are sequence tagged sites derived from cDNAs. See: sequence tagged site. Acronym: EST (06 Aug 1998) |
| flanking sequence | <molecular biology> Short DNA sequences bordering a transcription unit. Often these do not code for proteins. (18 Nov 1997) |
| leader sequence | <molecular biology> In the regulation of gene expression for enzymes concerned with amino acid synthesis in prokaryotes, the leader sequence codes for the leader peptide that contains several residues of the amino acid being regulated. Transcription is closely linked to translation and if translation is retarded by limited supply of amino acyl tRNA for the specific amino acid, the mode of transcription of the leader sequence permits full transcription of the operon genes, otherwise complete transcription of the leader sequence prematurely terminates transcription of the operon. (18 Nov 1997) |