Fig. 2. Backward forces on trailing arms cause a detached acentric arm fragment to move towards its partner. (A-D) Selected frames from a time-lapse series of an operation that generated an acentric fragment from a trailing arm during anaphase. (A) Before the operation. (B) Following the operation, the acentric fragment (arrowhead) moved backwards towards its partner with an initial velocity of 8 µm/minute. (C) The fragment crossed the equator and as its velocity decreased, it made contact with its partner (D). (E) As anaphase progressed, the fragment moved along with its partner to the opposite pole. Times are given in minutes and seconds. Bar, 5 µm (E). (F) A kinetic plot of the distance between the telomere of an acentric arm fragment (not depicted) and its partner telomere following laser microsurgery (arrow) as a function of time. The backward motion of the tethered fragment exhibited decreased velocity as the fragment approached its partner in the opposite half spindle prior to making contact, when the distance between telomeres became zero.