Cell Cycle
The process of cell growth
that results in cell division
to form an identical copy of
itself
Phases of Cell Cycle
Cell Cycle
Cell growth
Cell division
( Interphase)
(Mitosis)
Interphase – Cell growth
• Cell growth and copying of DNA in preparation for
cell division.
• Cell spends about 90% of the cell cycle in this phase
• Can be divided into sub phases:
• G1 phase (“first gap” or 1st growth phase)
• S phase (“ DNA synthesis”)
nd
• G2 phase (“second gap” or 2 growth phase)
Phases of Cell Cycle
Cell Cycle
90%
10%
Cell growth
Cell division
( Interphase)
(Mitosis)
G1 Phase
S Phase
G2 Phase
Interphase
• G1 Phase
• Cell grows in
size
• Protein
synthesis
• Nucleus intact
• Whole cell is
actively growing
• S Phase
• DNA synthesis
• Replication of
DNA
• 2 copies of
each DNA.
• G2 Phase
• Cell grows
• Prepare for cell
division
• Proteins made that
are needed for cell
division.
• Centromere appear
in animal cells
Organization of
DNA
G1-Phase (Chromatin)
DNA+Histone -> coil ->chromatin
S-Phase ( daughter DNA strand)
Chromatin->(unwind)-> replicate-> 2
daughter DNA strand
G2-Phase (forming Chromatids)
2daughter DNA-> condense-> 2 sister
chromatids
Mitosis ( Chromatids->chromosomes)
Sister chromatids->condense->
chromosome
Sister chromatids linked at “Centromere”
Interphase
• G1 Phase
• S Phase
• Cell grows in size
• Protein synthesis
• Nucleus intact
• Whole cell is actively
growing
• DNA synthesis
• Replication of DNA
• 2 copies of each
DNA.
1 set of DNA(chromatin)
2 sets of daughter DNA
• G2 Phase
• Cell grows
• Prepare for cell
division
• Proteins made that
are needed for cell
division.
• Centromere appear
in animal cells
Daughter DNA strands
condenses to form 2
sister chromatid
Overview: The Key Roles of Cell
Division
• The ability of organisms to reproduce best
distinguishes living things from non-living matter
• Growth and development of organism from an
egg to an adult require that cells divide and
grow.
• Tissue repair and renewal
•Chromatin to chromosomes illustration:
Chromatin
G1 Phase
Duplicates
itself
S Phase
Coils up into
chromosomes
G2-M Phase
Why does DNA need to change
More efficient division
from chromatin to chromosome?
o 2 identical “sister”
chromatids attached at
an area in the middle
called a centromere
o When cells divide,
“sister” chromatids
separate and 1 goes to
each new cell
Interphase
• G1 Phase
1 set of DNA(chromatin)
• S Phase
• G2 Phase
2 sets of daughter DNA
Daughter DNA strands
condenses to form 2
sister chromatid
Cell Division—Mitosis Notes
Cell Division — process by which
a cell divides into 2 new cells
• Why do cells need to divide?
1.If cell gets too big, it cannot
get enough nutrients into the
cell and wastes out of the cell
Phases of Cell Cycle
90%
10%
Cell Cycle
Cell growth
Cell division
( Interphase)
(Mitosis)
G1 Phase
S Phase
G2 Phase
Prophase
Metaphase
Anaphase
Telophase
Mitosis
• Nuclear division
• Involves DNA getting separated into two distinct
nucleus
• The original cell is called the parent cell; 2 new cells are
called daughter cells
• Each daughter cell is exactly like the parent cell – same
kind and number of chromosomes as the original cell
2
Daughter
Cells
Parent Cell
• 4 phases of nuclear division (mitosis), directed
by the cell’s DNA (PMAT)
Prophase
Metaphase—(Middle)
Anaphase—(Apart)
Anaphase—(Apart)
Telophase—(Two)
Prophase
Nuclear Envelope
Centriole
 Chromosomes coil
up
 Nuclear envelope
disappears
 Spindle fibers form
Spindle Fibers
Metaphase—(Middle)
 Chromosomes line up
in middle of cell
 Spindle fibers connect
to chromosomes
Anaphase—(Apart)
 Chromosome
copies divide
 Spindle fibers pull
chromosomes to
opposite poles
Telophase—(Two)
 Chromosomes uncoil
 Nuclear envelopes
form
 2 new nuclei are
formed
 Spindle fibers
disappear
Cytokinesis — the division of the rest of the cell
(cytoplasm and organelles) after the nucleus
divides
In animal cells the cytoplasm
pinches in
In plant cells a cell plate forms
Cell Plate
•After mitosis and cytokinesis, the cell returns to
Interphase to continue to grow and perform
regular cell activities
Phases of Cell Cycle
Cell Cycle
10%
90%
Cell growth
Cell division
( Interphase)
(Mitosis)
G1 Phase
S Phase
G2 Phase
Prophase
Metaphase
Cell division
(Cytokinesis)
Anaphase
Telophase
Cell Cycle
Cell Cycle Regulation
G0 Stage:
- Cell has decided not to divide
- Cell does all the normal function
G1 Check Point
- Between G1 and S phase
- Cell decides to divide or delay
division
G2 Checkpoint
- Between S phase and G2 phase
- Checks whether the DNA replication
was successful
M Checkpoint
- Between M phase and Cytokinesis
- Checks whether nuclear division was
successful
Mitosis Plant cells
Mitosis Animal cells