| chi site | <molecular biology> Short, active sequences of DNA which strongly encourages crossing over of chromosomes to occur at that site. These sites become chiasmata more often than other sites. (05 Jan 1998) |
|---|---|
| ribosome binding site | The region of a messenger RNA molecule that binds the ribosome to initiate translation. (09 Oct 1997) |
| cleavage site | A sequence in DNA that can be recognised and cut by a specific restriction enzyme. (12 Dec 1998) |
| combining site | <biochemistry, immunology> Any region of a molecule that binds or reacts with a given compound. Especially of the region of immunoglobulin that combines with the determinant of an appropriate antigen. (09 Jan 1998) |
| placental site trophoblastic tumour | A tumour usually arising in the uterus of parous women during reproductive years. Histologically, the tumour consists of a predominance of intermediate trophoblastic cells with fibrinoid material and vascular invasion. (05 Mar 2000) |
| Con A binding site | <biochemistry> A common misuse of the term receptor. Con A binds to the mannose residues of many different glycoproteins and glycolipids and the binding is therefore not to a specific site. It could be argued that the receptor is the Con A and cells have Con A ligands on their surfaces: certainly this would be less confusing. (05 Jan 1998) |
| multiple cloning site | Region of a phage or plasmid vector that has been engineered to contain a series of restriction sites that are usually unique within the entire vector. This makes it particularly easy to insert or excise (subclone) DNA fragments. (18 Nov 1997) |
| mutagenesis, site-directed | Mutagenesis where the mutation is caused by in vitro induction directed at a specific site in a DNA molecule. The most common method involves use of a chemically synthesised oligonucleotide mutant which can hybridise with the DNA target molecule. The resulting mismatch-carrying DNA duplex may then be transfected into a bacterial cell line and the mutant strands recovered. (12 Dec 1998) |
| polycloning site | Region of a phage or plasmid vector that has been engineered to contain a series of restriction sites that are usually unique within the entire vector. This makes it particularly easy to insert or excise (subclone) DNA fragments. (18 Nov 1997) |
| cos site | <molecular biology> A 12-nucleotide bases-long segment of single stranded DNA that exists at both ends of the bacteriophage lambda's double-stranded genome. The two cos sites at the ends of the genome are complementary to one another so that the genome can become circular once the virus has infected a host bacterium. The circular genome can then be duplicated continuously until there are many repeats of it strung together, the cos sites show the virus where to cut them apart right before they are packaged into individual capsids as new progeny viruses ready to infect more host cells. (10 Nov 1998) |
| privileged site | An anatomic area lacking lymphatic drainage, such as the brain, cornea, and hamster cheek pouch, in which heterologous tumours may grow because the host does not become sensitised. (05 Mar 2000) |
| P site | <molecular biology> The peptidyl tRNA binding site on the ribosome, the one to which the growing chain is attached, the incoming aminoacyl tRNA attaches to the A site. (18 Nov 1997) |
| secondary site | A second site in which cancer is found. Example: cancer in the lymph nodes near the breast is a secondary site. (09 Oct 1997) |
| sequence tagged site | <molecular biology> Short (200 to 500 base pairs) DNA sequence that has a single occurrence in the human genome and whose location and base sequence are known. Detectable by PCR, sequence tagged sites are useful for localising and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome. Expressed sequence tags are sequence tagged sites derived from cDNAs. (11 Jun 1998) |
| sequence-tagged site map | A map representing the order and spacing of sequence-tagged sites within a stretch of DNA. (05 Mar 2000) |