| axis of symmetry | An axis through a particle (e.g., a virus) on such a plane that, if the particle is rotated on the axis, there are two or more positions at which the particle appears identical. (05 Mar 2000) |
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| bilateral symmetry | <biology> Describes an organism which is divisible into equal mirror halves in one plane only. (09 Oct 1997) |
| pseudo-symmetry | <chemistry> A kind of symmetry characteristic of certain crystals which from twinning, or other causes, come to resemble forms of a system other than that to which they belong, as the apparently hexagonal prisms of aragonite. Origin: Pseudo- + symmetry. Source: Websters Dictionary (01 Mar 1998) |
| symmetry | 1. A due proportion of the several parts of a body to each other; adaptation of the form or dimensions of the several parts of a thing to each other; the union and conformity of the members of a work to the whole. 2. <biology> The law of likeness; similarity of structure; regularity in form and arrangement; orderly and similar distribution of parts, such that an animal may be divided into parts which are structurally symmetrical. Bilateral symmetry, or two-sidedness, in vertebrates, etc, is that in which the body can be divided into symmetrical halves by a vertical plane passing through the middle; radial symmetry, as in echinoderms, is that in which the individual parts are arranged symmetrically around a central axis; serial symmetry, or zonal symmetry, as in earthworms, is that in which the segments or metameres of the body are disposed in a zonal manner one after the other in a longitudinal axis. This last is sometimes called metamerism. 3. <botany> Equality in the number of parts of the successive circles in a flower. Likeness in the form and size of floral organs of the same kind; regularity. Axis of symmetry. <geometry> See Axis. Respective symmetry, that disposition of parts in which only the opposite sides are equal to each other. Origin: L. Symmetria, Gr.; with, together + a measure: cf. F. Symetrie. See Syn-, and Meter rhythm. Source: Websters Dictionary (01 Mar 1998) |
| symmetry axis | <radiobiology> The straight line (usually vertical) through the centre of a configuration, when the configuration is symmetric to all (axisymmetric, like the tokamak) or some (periodic, like the stellarator) rotations about this line. Usually the z-axis. (09 Oct 1997) |
| dyad symmetry element | Dyad symmetry element bound by serum response factor to control the expression of c fos. (18 Nov 1997) |
| dyad symmetry of DNA | <molecular biology> Two areas of a DNA molecule whose base pair sequences are repeats of each other, inverted relative to each other, or are palindromes. (09 Oct 1997) |
| inverse symmetry | Correspondence of the right or left side of an asymmetrical individual to the left or right side of another. (05 Mar 2000) |