The fission yeast Schizosaccharomyces pombe is widely used as a model system for studies of the cell cycle and chromosome biology. To enhance these studies we have fused GFP to the chromodomain protein Swi6p, thus allowing nuclear and chromosome behaviour to be followed in living cells using time-lapse fluorescence microscopy. Like endogenous Swi6p, GFP-Swi6p localises to the nucleus and is concentrated at the heterochromatic centromeres and telomeres. The nucleus is highly dynamic during interphase: the clustered centromeres, in particular, are highly mobile. By expressing GFP-(α)2-tubulin and GFP-Swi6p in the same cells we observe that the clustered centromeres move in concert with the cytoplasmic microtubules, which is likely to reflect their association with the spindle pole body. Drug treatment indicates that this movement is dependent on intact cytoplasmic microtubules. We have also used GFP-Swi6p to investigate the properties of lagging chromosomes observed in mutants with defects in chromosome segregation. Lagging chromosomes display a variety of behaviours on anaphase spindles, most surprisingly, chromosomes appear to initiate microtubule interactions and move to the poles late in anaphase B. Interestingly, in cells displaying lagging chromosomes, the rate of spindle elongation is slowed by a factor of two. This suggests that cells are able to sense the presence of a lagging chromosome and slow anaphase B in order to allow it extra time to reach the pole. However, this mechanism is not dependent on the spindle checkpoint proteins Bub1p or Dma1p, raising the possibility that a novel checkpoint mechanism operates to retard spindle elongation if lagging chromosomes are detected. An alternative model is also discussed in which single defective kinetochores on lagging chromatids are able to interact simultaneously with microtubules emanating from both poles and affect spindle dynamics by counteracting the spindle elongation force.

Allshire
R. C.
,
Javerzat
J.-P.
,
Redhead
N. J.
,
Cranston
G.
 (
1994
).
Position effect variegation at fission yeast centromeres.
Cell
76
,
157
–
169
Google Scholar
Crossref
Search ADS
 
Allshire
R. C.
 (
1995
).
Elements of chromosome structure and function in fission yeast.
Semin. Cell Biol
6
,
55
–
64
Google Scholar
Crossref
Search ADS
 
Allshire
R. C.
,
Nimmo
E. R.
,
Ekwall
K.
,
Javerzat
J.-P.
,
Cranston
G.
 (
1995
).
Mutations derepressing silent centromeric domains in fission yeast disrupt chromosome segregation.
Genes Dev
9
,
218
–
233
Google Scholar
Crossref
Search ADS
 
Alexandru
G.
,
Zachariae
W.
,
Schleiffer
A.
,
Nasmyth
K.
 (
1999
).
Sister chromatid separation and chromosome re-duplication are regulated by different mechanisms in response to spindle damage.
EMBO J
18
,
2707
–
2721
Google Scholar
Crossref
Search ADS
 
Andersen
S. S.
,
Ashford
A. J.
,
Tournebize
R.
,
Gavet
O.
,
Sobel
A.
,
Hyman
A. A.
,
Karsenti
E.
 (
1997
).
Mitotic chromatin regulates phosphorylation of Stathmin/Op18.
Nature
389
,
640
–
643
Google Scholar
Crossref
Search ADS
 
Basi
G.
,
Schmid
E.
,
Maundrell
K.
 (
1993
).
TATA box mutations in the Schizosaccharomyces pombenmt1 promoter affect transcription efficiency but not the transcription start point or thiamine repressibility.
Gene
123
,
131
–
136
Google Scholar
Crossref
Search ADS
 
Baum
M.
,
Ngan
V. K.
,
Clarke
L.
 (
1994
).
The centromeric K-type repeat and the central core are together sufficient to establish a functional Schizosaccharomyces pombe centromere.
Mol. Biol. Cell
5
,
747
–
761
Google Scholar
Crossref
Search ADS
 
Beltraminelli
N.
,
Murone
M.
,
Simanis
V.
 (
1999
).
The S. pombe zfs1 gene is required to prevent septation if mitotic progression is inhibited.
J. Cell Sci
112
,
3103
–
3114
Google Scholar
 
Bernard
P.
,
Hardwick
K.
,
Javerzat
J.-P.
) (
1998
).
Fission yeast Bub1 is a mitotic centromere protein essential for the spindle checkpoint and the preservation of correct ploidy through mitosis.
J. Cell Biol
143
,
1775
–
1787
Google Scholar
Crossref
Search ADS
 
Brinkley
B. R.
,
Zinkowski
R. P.
,
Mollon
W. L.
,
Davis
F. M.
,
Pisegna
M. A.
,
Pershouse
M.
,
Rao
P. N.
 (
1988
).
Movement and segregation of kinetochores experimentally detached from mammalian chromosomes.
Nature
336
,
251
–
254
Google Scholar
Crossref
Search ADS
 
Cande
W. Z.
,
McDonald
K. L.
 (
1985
).
In vitro reactivation of anaphase spindle elongation using isolated diatom spindles.
Nature
316
,
168
–
170
Google Scholar
Crossref
Search ADS
 
Chikashige
Y.
,
Ding
D. Q.
,
Funabiki
H.
,
Haraguchi
T.
,
Mashiko
S.
,
Yanagida
M.
,
Hiraoka
Y.
 (
1994
).
Telomere-led premeiotic chromosome movement in fission yeast.
Science
264
,
270
–
273
Google Scholar
Crossref
Search ADS
 
Chikashige
Y.
,
Ding
D.-Q.
,
Imai
Y.
,
Yamamoto
M.
,
Haraguchi
T.
,
Hiraoka
Y.
 (
1997
).
Meiotic nuclear reorganization: switching the position of centromeres and telomeres in the fission yeast Schizosaccharomyces pombe.
EMBO J
16
,
193
–
202
Google Scholar
Crossref
Search ADS
 
Clarke
L.
,
Baum
M.
,
Marschall
L. G.
,
Ngan
V. K.
,
Steiner
N. C.
 (
1994
).
Structure and function of Schizosaccharomyces pombe centromeres.
Cold Spring Harbor Symp. Quant. Biol
58
,
687
–
695
Google Scholar
Crossref
Search ADS
 
Ding
D. Q.
,
Chikashige
Y.
,
Haraguchi
T.
,
Hiraoka
Y.
 (
1998
).
Oscillatory nuclear movement in fission yeast meiotic prophase is driven by astral microtubules, as revealed by continuous observation of chromosomes and microtubules in living cells.
J. Cell Sci
111
,
701
–
712
Google Scholar
 
Ding
R.
,
McDonald
K. L.
,
McIntosh
J. R.
 (
1993
).
Three-dimensional reconstruction and analysis of mitotic spindles from the yeast, Schizosaccharomyces pombe.
J. Cell Biol
120
,
141
–
151
Google Scholar
Crossref
Search ADS
 
Ding
R.
,
West
R. R.
,
Morphew
D. M.
,
Oakley
B. R.
,
McIntosh
J. R.
 (
1997
).
The spindle pole body of Schizosaccharomyces pombe enters andleaves the nuclear envelope as the cell cycle proceeds.
Mol. Biol Cell
8
,
1461
–
1479
Google Scholar
Crossref
Search ADS
 
Dobie
K. W.
,
Hari
K. L.
,
Maggert
K. A.
,
Karpen
G. H.
 (
1999
).
Centromere proteins and chromosome inheritance: a complex affair.
Curr. Opin. Genet. Dev
9
,
206
–
217
Google Scholar
Crossref
Search ADS
 
Doe
C. L.
,
Wang
G.
,
Chow
C.
,
Fricker
M.
,
Singh
P. B.
,
Mellor
E. J.
 (
1998
).
The fission yeast chromo domain encoding gene chp1+ is required for chromosome segregation and shows a genetic interaction with alpha tubulin.
Nucl. Acids Res
26
,
4222
–
4229
Google Scholar
Crossref
Search ADS
 
Ekwall
K.
,
Ruusala
T.
 (
1994
).
Mutations in rik1, clr2, clr3 and clr4 genes asymmetrically derepress the silent mating-type loci in fission yeast.
Genetics
136
,
53
–
64
Google Scholar
 
Ekwall
K.
,
Javerzat
J.-P.
,
Lorentz
K.
,
Schmidt
H.
,
Cranston
G.
,
Allshire
R.
 (
1995
).
The chromo domain protein Swi6: A key component at fission yeast centromeres.
Science
269
,
1429
–
1431
Google Scholar
Crossref
Search ADS
 
Ekwall
K.
,
Nimmo
E. R.
,
Javerzat
J.-P.
,
Borgström
B.
,
Egel
R.
,
Cranston
G.
,
Allshire
R.
 (
1996
).
Mutations in the fission yeast silencing factors clr4 +and rik1 +disrupt the localisation of the chromo domain protein Swi6p and impair centromere function.
J. Cell Sci
109
,
2637
–
2648
Google Scholar
 
Ekwall
K.
,
Olsson
T.
,
Turner
B. M.
,
Cranston
G.
,
Allshire
R. C.
 (
1997
).
Transient inhibition of histone acetylation alters the structural and functional imprint at fission yeast centromeres.
Cell
91
,
1021
–
1032
Google Scholar
Crossref
Search ADS
 
Ekwall
K.
,
Cranston
G.
,
Allshire
R. C.
 (
1999
).
Novel fission yeast mutants which alleviate transcriptional silencing in centromeric flanking repeats and disrupt chromosome segregation.
Genetics
153
,
1153
–
1169
Google Scholar
 
Fankhauser
C.
,
Marks
J.
,
Reymond
A.
,
Simanis
V.
 (
1993
).
The S. pombe cdc16 gene is required both for maintenance of p34cdc2 kinase activity and regulation of septum formation: a link between mitosis and cytokinesis?.
EMBO J
12
,
2697
–
2704
Google Scholar
Crossref
Search ADS
 
Fesquet
D.
,
Fitzpatrick
P. J.
,
Johnson
A. L.
,
Kramer
K. M.
,
Toyn
J. H.
,
Johnston
L. H.
 (
1999
).
A Bub2p-dependent spindle checkpoint pathway regulates the Dbf2p kinase in budding yeast.
EMBO J
18
,
2424
–
2434
Google Scholar
Crossref
Search ADS
 
Fraschini
R.
,
Formenti
E.
,
Lucchini
G.
,
Piatti
S.
 (
1999
).
Budding yeast Bub2 is localized at spindle pole bodies and activates the mitotic checkpoint via a different pathway from Mad2.
J. Cell Biol
145
,
979
–
991
Google Scholar
Crossref
Search ADS
 
Fuge
H.
 (
1972
).
Morphological studies on the structure of univalent sex chromosomes during anaphase movement in spermatocytes of the crane fly Pales ferruginea.
Chromosoma
39
,
403
–
417
Google Scholar
Crossref
Search ADS
 
Funabiki
H.
,
Hagan
I.
,
Uzawa
S.
,
Yanagida
M.
 (
1993
).
Cell cycle-dependent specific positioning and clustering of centromeres and telomeres in fission yeast.
J. Cell Biol
121
,
961
–
976
Google Scholar
Crossref
Search ADS
 
Goshima
G.
,
Saitoh
S.
,
Yanagida
M.
 (
1999
).
Proper metaphase spindle length is determined by centromere proteins Mis12 and Mis6 required for faithful chromosome segregation.
Genes Dev
13
,
1664
–
1677
Google Scholar
Crossref
Search ADS
 
Gould
K. L.
,
Simanis
V.
 (
1997
).
The control of septum formation in fission yeast.
Genes Dev
11
,
2939
–
2951
Google Scholar
Crossref
Search ADS
 
Gunawardena
S.
,
Rykowski
M. C.
 (
2000
).
Direct evidence for interphase chromosome movement during the mid-blastula transition in Drosophila.
Curr. Biol
10
,
285
–
288
Google Scholar
Crossref
Search ADS
 
Hagan
I. M.
 (
1998
).
The fission yeast microtubule cytoskeleton.
J. Cell Sci
111
,
1603
–
1612
Google Scholar
 
Hagan
I. M.
,
Hyams
J. S.
 (
1988
).
The use of cell division cycle mutants to investigate the control of microtubule distribution in the fission yeast Schizosaccharomyces pombe.
J. Cell Sci
89
,
343
–
357
Google Scholar
 
Hagan
I. M.
,
Riddle
P. N.
,
Hyams
J. S.
 (
1990
).
Intramitotic controls in the fission yeast Schizosaccharomyces pombe: the effect of cell size on spindle length and the timing of mitotic events.
J. Cell Biol
110
,
1617
–
1621
Google Scholar
Crossref
Search ADS
 
Hagan
I.
,
Yanagida
M.
 (
1995
).
The product of the spindle formation gene sad1+ associates with the fission yeast spindle pole body and is essential for viability.
J. Cell Biol
129
,
1033
–
1047
Google Scholar
Crossref
Search ADS
 
Hagan
I.
,
Yanagida
M.
 (
1997
).
Evidence for cell cycle-specific, spindle pole body-mediated, nuclear positioning in the fission yeast Schizosaccharomyces pombe.
J. Cell Sci
110
,
1851
–
1866
Google Scholar
 
Hahnenberger
K. M.
,
Carbon
J.
,
Clarke
L.
 (
1991
).
Identification ofDNA regions required for mitotic and meiotic functions within the centromere of Schizosaccharomyces pombe chromosome I.
Mol. Cell. Biol
11
,
2206
–
2215
Google Scholar
Crossref
Search ADS
 
He
X.
,
Patterson
T. E.
,
Sazer
S.
 (
1997
).
The Schizosaccharomyces pombe spindle checkpoint protein Mad2p blocks anaphase and genetically interacts with the anaphase-promoting complex.
Proc. Nat. Acad. Sci. USA
94
,
7965
–
7970
Google Scholar
Crossref
Search ADS
 
He
X.
,
Jones
M. H.
,
Winey
M.
,
Sazer
S.
 (
1998
).
Mph1, a member of the Mps1-like family of dual specificity protein kinases, is required for the spindle checkpoint in S. pombe.
J Cell Sci
111
,
1635
–
1647
Google Scholar
 
Ivanova
A. V.
,
Bonaduce
M. J.
,
Ivanov
S. V.
,
Klar
A. J.
 (
1998
).
The chromo and SET domains of the Clr4 protein are essential for silencing in fission yeast.
Nature Genet
19
,
192
–
195
Google Scholar
Crossref
Search ADS
 
Janicke
M. A.
,
LaFountain
J. R.
Jr. (
1984
).
Malorientation in half-bivalents at anaphase: analysis of autosomal laggards in untreated, cold-treated, and cold-recovering crane fly spermatocytes.
J. Cell Biol
98
,
859
–
869
Google Scholar
Crossref
Search ADS
 
Khodjakov
A.
,
Cole
R. W.
,
McEwen
B. F.
,
Buttle
K. F.
,
Rieder
C. L.
 (
1997
).
Chromosome fragments possessing only one kinetochore can congress to the spindle equator.
J. Cell Biol
136
,
229
–
240
Google Scholar
Crossref
Search ADS
 
Kim
S. H.
,
Lin
D. P.
,
Matsumoto
S.
,
Kitazono
A.
,
Matsumoto
T.
 (
1998
).
Fission yeast Slp1: an effector of the Mad2-dependent spindle checkpoint.
Science
279
,
1045
–
1047
Google Scholar
Crossref
Search ADS
 
Ladrach
K. S.
,
LaFountain
J. R.
Jr. (
1986
).
Malorientation and abnormal segregation of chromosomes during recovery from colcemid and nocodazole.
Cell Motil. Cytoskel
6
,
419
–
427
Google Scholar
Crossref
Search ADS
 
Li
R.
 (
1999
).
Bifurcation of the mitotic checkpoint pathway in budding yeast.
Proc. Nat. Acad. Sci. USA
96
,
4989
–
4994
Google Scholar
Crossref
Search ADS
 
Lorentz
A.
,
Heim
L.
,
Schmidt
H.
 (
1992
).
The switching gene swi6 affects recombination and gene expression in the mating-type region of Schizosaccharomyces pombe.
Mol. Gen. Genet
233
,
436
–
442
Google Scholar
Crossref
Search ADS
 
Lorentz
A.
,
Osterman
K.
,
Fleck
O.
,
Schmidt
H.
 (
1994
).
Switching gene swi6, involved in repression of silent mating type loci in fission yeast, encodes a homologue of chromatin-associated proteins from Drosophila and mammals.
Gene
143
,
139
–
143
Google Scholar
Crossref
Search ADS
 
Mallavarapu
A.
,
Sawin
K.
,
Mitchison
T.
 (
1999
).
A switch in microtubule dynamics at the onset of anaphase B in the mitotic spindle of Schizosaccharomyces pombe.
Curr. Biol
9
,
1423
–
1426
Google Scholar
Crossref
Search ADS
 
Marshall
W. F.
,
Straight
A.
,
Marko
J. F.
,
Swedlow
J.
,
Dernburg
A.
,
Belmont
A.
,
Murray
A. W.
,
Agard
D. A.
,
Sedat
J. W.
 (
1997
).
Interphase chromosomes undergo constrained diffusional motion in living cells.
Curr. Biol
7
,
930
–
939
Google Scholar
Crossref
Search ADS
 
Masuda
H.
,
Hirano
T.
,
Yanagida
M.
,
Cande
W. Z.
 (
1990
).
In vitro reactivation of spindle elongation in fission yeast nuc2 mutant cells.
J. Cell Biol
110
,
417
–
425
Google Scholar
Crossref
Search ADS
 
Maundrell
K.
 (
1993
).
Thiamine-repressible expression vectors pREP and pRIP for fission yeast.
Gene
123
,
127
–
130
Google Scholar
Crossref
Search ADS
 
Moreno
S.
,
Klar
A. J. S.
,
Nurse
P.
 (
1991
).
Molecular genetic analysis of fission yeast Schizosaccharomyces pombe.
Meth. Enzymol
194
,
795
–
823
Google Scholar
Crossref
Search ADS
 
Murone
M.
,
Simanis
V.
 (
1996
).
The fission yeast dma1 gene is a component of the spindle assembly checkpoint, required to prevent septum formation and premature exit from mitosis if spindle function is compromised.
EMBO J
15
,
6605
–
6616
Google Scholar
Crossref
Search ADS
 
Nabeshima
K.
,
Saitoh
S.
,
Yanagida
M.
 (
1997
).
Use of green fluorescent protein for intracellular protein localization in living fission yeast cells.
Meth. Enzymol
283
,
459
–
471
Google Scholar
Crossref
Search ADS
 
Nabeshima
K.
,
Nakagawa
T.
,
Straight
A. F.
,
Murray
A.
,
Chikashige
Y.
,
Yamashita
Y. M.
,
Hiraoka
Y.
,
Yanagida
M.
 (
1998
).
Dynamics of centromeres during metaphase-anaphase transition in fission yeast: Dis1 isimplicated in force balance in metaphase bipolar spindle.
Mol. Biol. Cell
9
,
3211
–
3225
Google Scholar
Crossref
Search ADS
 
Ngan
V. K.
,
Clarke
L.
 (
1997
).
The centromere enhancer mediates centromere activation in Schizosaccharomyces pombe.
Mol. Cell. Biol
17
,
3305
–
3314
Google Scholar
Crossref
Search ADS
 
Nimmo
E. R.
,
Pidoux
A. L.
,
Perry
P. E.
,
Allshire
R. C.
 (
1998
).
Defective meiosis in telomere-silencing mutants of Schizosaccharomyces pombe.
Nature
392
,
825
–
828
Google Scholar
Crossref
Search ADS
 
Paro
R.
,
Hogness
D. S.
 (
1991
).
The polycomb protein shares a homologous domain with a heterochromatin-associated protein of Drosophila.
Proc. Nat. Acad. Sci. USA
88
,
263
–
267
Google Scholar
Crossref
Search ADS
 
Partridge
J. F.
,
Borgstrom
B.
,
Allshire
R. C.
 (
2000
).
Distinct protein interaction domains and protein spreading in a complex centromere.
Genes Dev
14
,
783
–
791
Google Scholar
 
Pidoux
A. L.
,
Armstrong
J.
 (
1992
).
Analysis of the BiP gene and identification of an ER retention signal in Schizosaccharomyces pombe..
EMBO J
11
,
1583
–
1591
Google Scholar
Crossref
Search ADS
 
Pidoux
A. L.
,
Allshire
R. C.
 (
2000
).
Centromeres: getting a grip of chromosomes.
Curr. Opin. Cell Biol
12
,
308
–
319
Google Scholar
Crossref
Search ADS
 
Saitoh
S.
,
Takahashi
K.
,
Yanagida
M.
 (
1997
).
Mis6, a fission yeast inner centromere protein, acts during G1/S and forms specialised chromatin required for equal segregation.
Cell
90
,
131
–
143
Google Scholar
Crossref
Search ADS
 
Shelby
R. D.
,
Hahn
K. M.
,
Sullivan
K. F.
 (
1996
).
Dynamic elastic behavior of alpha-satellite DNA domains visualized in situ in living human cells.
J. Cell Biol
135
,
545
–
557
Google Scholar
Crossref
Search ADS
 
Steiner
N. S.
,
Clarke
L.
 (
1994
).
A novel epigenetic affect can alter centromere function in fission yeast.
Cell
79
,
865
–
874
Google Scholar
Crossref
Search ADS
 
Takahashi
K.
,
Murakami
S.
,
Chikashige
Y.
,
Funabiki
H.
,
Niwa
O.
,
Yanagida
M.
 (
1992
).
A low copy number central sequence with strict symmetry and unusual chromatin structure in fission yeast centromere.
Mol. Biol. Cell
3
,
819
–
835
Google Scholar
Crossref
Search ADS
 
Takahashi
K.
,
Yamada
H.
,
Yanagida
M.
 (
1994
).
Fission yeast minichromosome loss mutants mis cause lethal aneuploidy and replication abnormality.
Mol. Biol. Cell
5
,
1145
–
1158
Google Scholar
Crossref
Search ADS
 
Tanaka
K.
,
Kanbe
T.
 (
1986
).
Mitosis in the fission yeast Schizosaccharomyces pombe as revealed by freeze-substitution electron microscopy.
J. Cell Sci
80
,
253
–
268
Google Scholar
 
Taylor
S. S.
 (
1999
).
Chromosome segregation: dual control ensures fidelity.
Curr. Biol
9
,
562
–
564
Google Scholar
Crossref
Search ADS
 
Trelles-Sticken
E.
,
Loidl
J.
,
Scherthan
H.
 (
1999
).
Bouquet formation in budding yeast: initiation of recombination is not required for meiotic telomere clustering.
J. Cell Sci
112
,
651
–
658
Google Scholar
 
Wadsworth
P.
,
Shelden
E.
,
Rupp
G.
,
Rieder
C. L.
 (
1989
).
Biotin-tubulin incorporates into kinetochore fiber microtubules during early but not late anaphase.
J. Cell Biol
.
109
,
2257
–
2265
.
Google Scholar
Crossref
Search ADS
 
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Fig. 2A

graphic

Dynamic movement of the fission yeast. Sequence of interphase (G2) cell expressing GFP-Swi6p (HM123P) obtained with DeltaVision deconvolution light microscope. Images are projections of stack of images through the cell that have been subjected to iterative deconvolution. The time interval between stacks is 1 minute. The other, less mobile, GFP-Swi6p spots are the telomeres, and mating type locus.

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Fig. 2B

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Interphase (G2) cell expressing GFP-Swi6p and GFP-tubulin (strain 2693). A bright GFP-Swi6p spot (centromeres) moves in parallel with the cytoplasmic MTs.

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Fig. 2C

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Cell expressing GFP-Swi6p and GFP-tubulin. Centromere/SPB region associates with MTs of the post-anaphase array of MTs. The nucleus is deformed as it is dragged towards the centre of the daughter cell.

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Fig. 2D

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Time-lapse microscopy of strain 2693 (GFP-Swi6 and GFP-tubulin) was performed in the absence and presence of the microtubule-disrupting drug TBZ (cells go out of focus as TBZ is added and GFP labelled MTs disappear). Movement of bright centromeric GFP-Swi6 spots is dramatically reduced in the presence of TBZ.

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Fig. 3A

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Cell in mitosis progressing from early anaphase B though to movement of daughter nuclei back towards the new cell centres.

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Fig. 3B

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High resolution images taken from a sequence of a cell in early anaphase B. Individual centromeres can be distinguished at the poles.

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Fig. 3C

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Sequence obtained with DeltaVision light microscope of G2 cell entering mitosis. De-clustering of centromeres and telomeres at the start of mitosis can be clearly seen.

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Fig. 5A

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Normal mitosis in a mutant, no lagging chromosome.

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Fig. 5B

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Class 1: a chromosome lags behind the main mass of the upper daughter nucleus.

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Fig. 5C

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Class 1: a chromosome is observed lagging briefly but catches up.

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Fig. 5D

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Class 2: a chromosome fails to move towards either pole.

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Fig. 5E

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Class 3: a lagging chromosome fails to reach the pole during the period of observation.

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Fig. 5F

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Class 4: uneven segregation with a lagging chromosome moving to the bottom pole.

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Fig. 5G

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Class 5: a chromosome moves first towards the upper pole, then changes direction and moves to the lower pole.

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Fig. 5H

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Class 5: a chromosome moves first towards the upper pole, then changes direction, oscillates, and eventually joins with the upper daughter nucleus.

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Fig. 5I

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Class 6: a chromosome moves towards the upper pole, then moves towards the lower pole but becomes stranded between the mid-zone and the lower pole.

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Fig. 5J

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Class 6: a chromosome moves first towards the lower pole, but changes direction, oscillates and becomes stranded, a second chromosome moves away from the upper pole and also becomes stranded.

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Fig. 8

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csp10-2 csp10 cell with a lagging chromosome (strain 2493).

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