4 Phases of the Cell Cycle :
1. G1 (gap 1) - stage = Interphase
2. S phase - stage = Interphase
3. G2 (gap 2) - stage = Interphase
4. M phase - stages = Mitosis & Cytokinesis
Cell Cycle – Interphase, Mitosis, & Cytokinesis
Mitosis
Mitosis is divided into 4 phases :
1. Prophase – 1st phase (longest)
2. Metaphase – 2nd phase
3. Anaphase – 3rd phase
4. Telophase – 4th (final) phase
(think PMAT to recall order)
Prophase (first)
1. Prophase – the 1st and longest phase of
mitosis during which the :
A. Chromosomes condense & become
visible.
B. Centrioles move to opposite sides of the
nucleus.
C. Nucleolus disappears.
D. Nuclear membrane breaks down.
E. Spindle (fanlike structure that helps
separate chromosomes) forms.
F. Spindle fibers attach to centromeres of
chromosomes.
Metaphase
2. Metaphase – 2nd phase of
mitosis during which the
chromosomes line up across
the center of the cell.
(M&M : Meta = middle)
Anaphase
3. Anaphase – 3rd phase of
mitosis during which the
centromeres split &
individual chromatids
move toward the poles.
(AAA – in ANAPHASE
chromosomes are pulled
APART & move AWAY to
opposite sides).
Telophase (opposite of Prophase happens)
4. Telophase – 4th & final phase of
mitosis during which the :
A. Chromosomes uncoil into a
mass of material & can’t be seen.
B. Nuclear membrane re-forms
around each cluster of
chromosomes.
C. Spindles break apart.
D. Nucleolus becomes visible in
each daughter cell.
*Cytokinesis usually occurs at
the same time as Telophase.
Cytokinesis
Cytokinesis – division of cytoplasm.
-In animal cells cytokinesis occurs
by drawing in the cytoplasm until it
pinches into 2 parts (cleavage
furrow).
-In plant cells cytokinesis occurs
when a structure known as the cell
plate forms midway between the
divided nuclei.
The cell plate becomes a separating
membrane & the cell wall forms in it.
Plant Cell Mitosis