Download PANEL 18–1 The Principal Stages of M Phase (Mitosis and

PANEL 18–1 The Principal Stages of M Phase (Mitosis and Cytokinesis) in an Animal Cell
CELL DIVISION AND THE CELL CYCLE
INTERPHASE
INTERPHASE
microtubules
duplicated centrosome
S
G1
G2
cytosol
6 CYTOKINESIS
nuclear
envelope
1 PROPHASE
CELL
CYCLE
5
TELOPHASE
4
2 PROMETAPHASE
ANAPHASE
3 METAPHASE
plasma
membrane
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 (mitosis) and cytoplasmic division (cytokinesis).
In this figure, the M phase has been expanded for clarity.
Mitosis is itself divided into five stages, and these,
together with cytokinesis, are described in this panel.
1 PROPHASE
intact
nuclear
envelope
centrosome
forming
mitotic
spindle
kinetochore
condensing replicated chromosome, consisting of
two sister chromatids held together along their length
2 PROMETAPHASE
centrosome
at spindle
pole
kinetochore
microtubule
fragments of
nuclear envelope
The light micrographs shown in this panel are of a
living cell from the lung epithelium of a newt. The
same cell has been photographed when viewed by
differential-interference-contrast microscopy at
different times during its division into two daughter
cells. (Courtesy of Conly L. Rieder.)
At prophase, the replicated
chromosomes, each consisting
of two closely associated sister
chromatids, condense. Outside
the nucleus, the mitotic spindle
assembles between the two
centrosomes, which have replicated and moved apart. For
simplicity, only three
chromosomes are shown. In
diploid cells, there would be two
copies of each chromosome
present.
time = 0 min
Prometaphase starts
abruptly with the
breakdown of the nuclear
envelope. Chromosomes
can now attach to spindle
microtubules via their
kinetochores and undergo
active movement.
chromosome in active motion
time = 79 min