Mode of flagellum formation and relationship with the cell cycle. (A) In Chlamydomonas, the flagella are disassembled prior to mitosis during the asexual life cycle. (B) In the procyclic form of Trypanosoma brucei, a new flagellum is constructed while the old one remains in place. Mature and assembling flagella are shown in green and red, respectively (see text for details). The tip of the elongating flagellum is indicated with arrowheads and the plane of cleavage is shown by dotted lines.