- The place, in Latin.. In genetics, a locus is the place a gene occupies on a chromosome. One locus, two loci.
* * *1. A place; usually, a specific site. 2. The position that a gene occupies on a chromosome. 3. The position of a point, as defined by the coordinates on a graph. [L.]- l. caeruleus [TA] a shallow depression, of a blue color in the fresh brain, lying laterally in the most rostral portion of the rhomboidal fossa near the cerebral aqueduct; it lies near the lateral wall of the fourth ventricle and consists of about 20,000 melanin-pigmented neuronal cell bodies whose norepinephrine-containing axons have a remarkably wide distribution in the cerebellum as well as in the hypothalamus and cerebral cortex. SYN: l. cinereus, l. ferrugineus, substantia ferruginea.- l. cinereus SYN: l. caeruleus.- cis-acting l. a section of DNA that affects the activity of DNA sequences on that same molecule of DNA.- complex l. a set of closely linked genetic loci with a common function, as in the major histocompatibility complex l..- l. of control a theoretical construct designed to assess a person's perceived control over his/her own behavior; classified as internal if the person feels in control of events, external if others are perceived to have that control.- l. ferrugineus SYN: l. caeruleus.- genetic l. the set of homologous parts of a pair of chromosomes that may be occupied by allelic genes. The l. thus comprises a pair of locations (except in the X chromosome in males). The concept of a l. is somewhat idealized, not taking into account accidents that may occur in meiosis such as duplication of loci as a result of unequal crossing-over, translocations, inversions, etc.- marker l. a l. on a chromosome or in a stretch of DNA that can be identified ( e.g., a restriction fragment length polymorphism) and can serve in linkage analysis and in the isolation of a disease gene. SEE ALSO: linkage marker.- sex-linked l. any l. that in normal karyotypes is borne on a heterosome; commonly but incorrectly applied to an X-linked l..- Y-linked l. any (haploid) l. that in normal karyotypes is borne on the Y chromosome. The known content is so far small.
* * *1) a place or site of an event, activity, or thing <the integrity of the tissues determines the extent and \locus of the damage (Sylvia E. Hines)>2) the position in a chromosome of a particular gene or allele
* * *n.1. (in anatomy) a region or site. The locus caeruleus is a small pigmented region in the floor of the fourth ventricle of the brain.
* * *lo·cus (loґkəs) gen. and pl. loґci [L. â€œa placeâ€] 1. a place or site, as in the body. 2. in genetics, the position of a gene on a chromosome, different forms of genes (alleles) being found at the same position on homologous chromosomes. The standard method of designating a locus consists of the chromosome number; p (short arm) or q (long arm); region and band number written without separation (11, 12, 13, etc.), moving outward from the centromere; sub-band and sub-sub-band, again written without separation. The centromere is designated by "cen" and the telomere or terminal by "ter."
Medical dictionary. 2011.