Normal transition of a dikinetid to a monokinetid in a control cell prior tobasal body duplication. In this case, the anterior basal body ofthe pair is linked to and uses the striated rootlet (SR) as a guide duringmovement. MKS3p is shown at each basal body near the cell surface (transitionzone–associated MKS3p) and also at the attachment of the anterior basalbody to the SR (SR-associated MKS3p). We propose that this second location ofMKS3p is temporary because MKS3p is not required as a guide once the anteriorbasal body has moved away from the posterior one sufficiently to develop itsrootlets and foster the growth of another basal body. The lower portion of thepanel diagrams the transition from a dikinetid to a monokinetid inMKS3-depleted cells. We propose that, in the absence of MKS3p, theanterior basal body loses its mooring and can no longer utilize the SR as aguide for migration. Without guidance, the basal body wanders out of alignment,resulting in skewed SRs, disorganized basal body rows and muddled corticalridge organization.