Genetics, Origin and Evolution of Kinetochores

HE term liinetochore (= movement place; SHARP, 1934) is used in T this paper to mean the specialized region of the clironiosonir~ wlicre tlie property of active riiobility on the spindle is manifested irrespective o f the number or extension of these regions in the clironiosoin(' body and of other properties tliat may be associated with tho region of active mobility.The expression localized hinetocliore is uwd when a single region is present in tlie clironiosoine body which manifests the property ot active mobility in conjunction with the property of a special cycle of division.The expres4ons diffuse and multiple liinetochores, respectivcly, arc' uwti to iimin the apparent distribution of tlie property of active mobility tlirougliout tlie whole body of the clironiosonie, and the existence ol' sevc.r:rldistinct regions in the cliroinosoine body t1i:i t have this property.TIic, propchrty of a special cycle of division c m n o t :ilways be recognized in llie first of these types.The term non-localizcd kinetochore i k , u s d when the type of kinetochore found is not a localized one, h i t when it may or m a y not be of the diffuse type.The term centromere is used as a syiionyni 01 localired ltinctochorcl bec:~use it has almost acquired this meaning in the literature.B r G h the term centroniere (understood a5 R region which is the cenlrc. of tlic forccs responsible for [he chromosome beliaviour during divisii bn) is mainly :I term having a genetic significance.Thus, tlie crossing-over per unit cytological length near the centroniere ic, 1owt.rthan elsewhere.'I'lit.term centromere lacks the universality necessary to embrace all tlic wgions in question.These regions havc~ in coniinon only one property.llic propcrty of active mobility, and among tlie existing terms, kinctocliorcmovenient placeis the one which expre best tlih plienonivnon.It has the advantage that it docs not iniply tlie existence ol' any specialized ))organ)) or ))body)) at this region of the chromoso~ne, arid it is independent of the structure of tlie region in question.I do not, Iiowevor, consider it an ideal term, but, as it is fairly good for the expo4tion 5 0 l l l C body.