Fig. 1. Segregation of a long compound chromosome. (A) Chromosome fusion through recombination of a bridging fragment [see (3) for details].
Circles indicate centromeres (black), TRP1 (red),
and LYS4 (green) loci; numbers indicate estimated
distances (Mb) to the active centromere. Chromosomes are not to scale. (B) Serial dilutions of log-phase cultures at 30°C for 48 hours (glucose) or
72 hours (galactose). Galactose inactivates the conditional centromere (pGAL). (C and D) Analysis of
SPBs (green, Spc42-GFP, asterisks), LYS4 (green), and
TRP1 (red) trajectories in wild-type and LC cells. Bud-directed chromatids are pulled away from their sisters
in the mother cell, which move comparatively less.
Arrowheads and arrows indicate segregation of TRP1
and LYS4, respectively. Time 0, anaphase onset. Scale
bars, 1 mm. (E) Spindle elongation dynamics (distance
between SPBs) in wild-type and LC(XII:IV)cen4Δ
cells (N = 20). The arrow marks spindle breakdown.
(F) Time of segregation (sister spots are separated
by >2 mm) relative to anaphase onset (left), or corresponding spindle length (right), for loci on the indicated chromosome, plotted against the distance to
the centromere. Nonlinear fit shows an asymptotic
relationship (N > 25). In (E) and (F), data points are
Fig. 2. Anaphase condensation is increased in the long compound chromosome. (A) Representative metaphase (left) and anaphase (right) cells with
labeled SPBs (large green dot), TRP1 (red), and LYS4 (green) loci. The positions of the fluorescent marks on the chromosomes are indicated (top) as
in Fig. 1. (B) Distance between the TRP1 and LYS4 spots [Δx in (A)] measured in time series in mother cells. (C) TRP1-LYS4 distances during metaphase (10 min before anaphase onset) and anaphase [shaded region in (B)]
in indicated compartments (N > 25). In these and the following graphs, boxes include 50% of data points, whiskers 95%. Median (lines) and mean (crosses)
are shown. Asterisks indicate P < 0.02 (*) or P < 0.001 (**). (D) TRP1-LYS4 distances [as in (C)] in depicted diploid cells (N > 20).