102
UNIT ONE
Telophase and Cytokinesis
Nuclear envelopes begin to
reassemble around two daughter
nuclei. Chromosomes decondense.
Spindle disappears. Division of
the cytoplasm into two cells.
Anaphase
Sister chromatids separate to
opposite poles of cell. Events
begin which lead to cytokinesis.
Metaphase
Chromosomes align along
equator, or metaphase plate
of cell.
Prophase
Chromosomes condense and
become visible. Nuclear
envelope and nucleolus
disperse. Spindle apparatus
forms.
Late Interphase
Cell has passed the
restriction checkpoint
and completed DNA
replication, as well as
replication of centrioles
and mitochondria, and
synthesis of extra
membrane.
Early Interphase
of daughter cells—
a time of normal cell
growth and function.
Cleavage
furrow
Nuclear
envelopes
Nuclear
envelope
Chromatin
fibers
Chromosomes
Spindle fiber
Centromere
Aster
Centrioles
Late prophase
Sister
chromatids
Microtubules
Mitosis
Cytokinesis
S phase
G
2
phase
G
1
phase
Interphase
Restriction
checkpoint
(a)
(b)
(c)
(d)
(e)
FIGURE 3.36
Mitosis and cytokinesis produce two cells from one. (
a
) During interphase, before mitosis, chromosomes are visible only as
chromatin F
bers. A single pair of centrioles is present, but not visible at this magniF
cation. (
b
) In prophase, as mitosis begins, chromosomes have
condensed and are easily visible when stained. The centrioles have replicated, and each pair moves to an opposite end of the cell. The nuclear
envelope and nucleolus disappear, and spindle F
bers associate with the centrioles and the chromosomes. (
c
)
In metaphase, the chromosomes
line up midway between the centrioles. (
d
) In anaphase, the centromeres are pulled apart by the spindle F
bers, and the chromatids, now individual
chromosomes, move in opposite directions. (
e
) In telophase, chromosomes complete their migration and become chromatin, the nuclear envelope
reforms, and microtubules disassemble. Cytokinesis, which began during anaphase, continues during telophase. Not all chromosomes are shown in
these drawings. (Micrographs approximately 360×)
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