spindle A structure formed from microtubules in the cytoplasm during cell division that moves chromatids (see mitosis) or chromosomes (see meiosis) diametrically apart and gathers them in two clusters at opposite ends (poles) of the cell. Broad in the middle and narrowing to a point at either pole, its construction is directed by a microtubule-organizing centre, the centrosome. In the preliminary stages of cell division the centrosome divides, and the two daughter centrosomes move to opposite poles. Each organizes three sets of microtubules (or ‘spindle fibres’): the first set consists of a tuft of fibres, called the aster, radiating towards the cell periphery; the second set extends towards the centre of the cell to attach to chromatids or chromosomes; the third set also extends through the centre to overlap with its counterpart from the opposite pole at the spindle equator, the region halfway between the poles. The spindle becomes fully formed by metaphase, when the chromatids are attached to spindle fibres via their centromeres and lie at the spindle equator. During anaphase this set of fibres shortens and hauls the attached chromatids towards the corresponding pole of the cell. Also, the overlapping fibres at the equator actively engage and slide past each other to elongate the entire spindle. See also muscle spindle.

spindle The set of microtubular fibres that appear to move the chromosomes of eukaryotes during cell division. The spindle is formed only at mitosis or meiosis, appearing at metaphase and first arranging the chromosomes at its equator. Movement apart of chromatids then occurs during anaphase, probably as a result of the spindle fibres, which run from the centromere (spindle attachment) to the spindle pole and from pole to pole, sliding past one another in a ratchetlike manner, similar to the way muscle filaments slide past each other (see SLIDING-FILAMENT THEORY).

spindle The set of microtubular fibres that appear to move the chromosomes of eukaryotes during cell division. The spindle is formed only at mitosis or meiosis, appearing at metaphase and first arranging the chromosomes at its equator. Movement apart of chromatids then occurs during anaphase, probably as a result of contraction of the fibres that run from the centromere (spindle attachment) to the spindle pole, and from pole to pole.

spindle •addle, paddle, saddle, skedaddle, staddle, straddle •candle, Coromandel, dandle, Handel, handle, mishandle, Randall, sandal, scandal, vandal •manhandle, panhandle •packsaddle • side-saddle •backpedal, heddle, medal, meddle, pedal, peddle, treadle •Grendel, Kendall, Lendl, Mendel, Rendell, sendal, Wendell •cradle, ladle •beadle, bipedal, credal, needle, wheedle •diddle, fiddle, griddle, kiddle, Liddell, middle, piddle, riddle, twiddle •brindle, dwindle, kindle, spindle, swindle, Tyndale •paradiddle, taradiddle •pyramidal • apsidal •bridal, bridle, fratricidal, genocidal, germicidal, homicidal, idle, idol, infanticidal, insecticidal, intertidal, matricidal, parricidal, patricidal, pesticidal, regicidal, sidle, suicidal, tidal, tyrannicidal, uxoricidal •coddle, doddle, model, noddle, swaddle, toddle, twaddle, waddle •fondle, rondel •mollycoddle •caudal, chordal, dawdle •poundal, roundel •Gödel, modal, yodel •crinoidal •boodle, caboodle, canoodle, doodle, feudal, noodle, poodle, strudel, udal •befuddle, cuddle, fuddle, huddle, muddle, puddle, ruddle •bundle, trundle •prebendal • synodal •antipodal, tripodal •citadel •curdle, engirdle, girdle, hurdle •dirndl

spindle slender rod serving to twist and wind thread in spinning OE.; rod serving as an axis XIV. OE. spinel, corr. to OS. spinnila, (M)Du. spindel, OHG. spin(n)ila, -ala (G. spindel), f. *spin- SPIN; see -LE1.

spindle (spin-d'l) n. a collection of fibres seen in a cell when it is dividing. It plays an important part in chromosome movement in mitosis and meiosis and is also involved in division of the cytoplasm.

spindle: see spinning.