Essential Cell Biology 5th edition

628
PANEL 18–1 THE PRINCIPAL STAGES OF M PHASE IN AN ANIMAL CELL
CELL DIVISION AND THE CELL CYCLE
INTERPHASE
S
G 1 G 2
INTERPHASE
cytosol
microtubules
duplicated centrosome
nuclear
envelope
CYTOKINESIS
5
TELOPHASE
4
ANAPHASE
CELL
CYCLE
MITOSIS
2
3
1 PROPHASE
PROMETAPHASE
METAPHASE
plasma
membrane
nucleolus
decondensed
chromosomes
in nucleus
During interphase, the cell increases in size. The DNA
of the chromosomes is replicated, and the
centrosome is duplicated.
M PHASE
The division of a cell into two daughters occurs in the
M phase of the cell cycle. M phase consists of nuclear division,
or mitosis, and cytoplasmic division, or cytokinesis. In this
figure, M phase has been greatly expanded for clarity. Mitosis is
itself divided into five stages, and these, together with
cytokinesis, are described in this panel.
In the light micrographs of dividing animal cells shown in
this panel, chromosomes are stained orange and
microtubules are green.
(Courtesy of Julie Canman and Ted Salmon.)
MITOSIS
1
intact
nuclear
envelope
kinetochore
PROPHASE
centrosome
forming
mitotic
spindle
At prophase, the
duplicated chromosomes,
each consisting of two
closely associated sister
chromatids, condense.
Outside the nucleus, the
mitotic spindle assembles
between the two
centrosomes, which have
begun to move apart. For
simplicity, only three
chromosomes are drawn.
condensing duplicated
chromosome with two sister
chromatids held together along their length
MITOSIS
2 PROMETAPHASE
Prometaphase starts
abruptly with the
spindle pole
breakdown of the nuclear
envelope. Chromosomes
can now attach to spindle
microtubules via their
kinetochores and undergo
active movement.
fragments of
nuclear envelope
kinetochore
microtubule
chromosome in motion
Panel 18.01a