The Cell Cycle
Sections 5.1-5.2
The cell cycle is a
regular pattern of
growth, DNA
replication, and
cell division.
Four Main Stages
• The cell cycle has four main stages:
1.
2.
3.
4.
Gap 1 (G1)
Synthesis (S)
Gap 2 (G2)
Mitosis (M)
•
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Interphase
First Stage: Gap 1
(G1)
– Cell carries out normal functions
• Ex: skeletal muscle cell contracts to move joints
– Cells also continue to grow during
this stage.
– Cells spend most of their time in this
stage.
• Length of this stage depends on the type of the cell
Second Stage: DNA synthesis
(S)
• DNA is copied
• At the end of the
synthesis stage, the
cell nucleus
contains two
complete sets of
DNA.
Third Stage: Gap 2 (G2)
•Cells continue to carry
out their normal
functions
•Additional growth
occurs
Fourth Stage: Mitosis (M)
• Includes two processes:
– Mitosis
• division of the cell and its contents
• During mitosis, the nuclear membrane dissolves, the
duplicated DNA condenses around proteins and separates,
and two nuclei form.
– Cytokinesis
• Process that divides the cell cytoplasm
• Result is two daughter cells that are genetically identical to
the original cell.
• Mitosis occurs only if the cell is
large enough and the DNA
undamaged.
• Cells divide at different rates.
–The rate of cell division varies with
the need for those types of cells.
–Some cells are unlikely to divide (G0).
• Cell size is limited.
–Volume increases faster than surface
area.
• Surface area must allow for
adequate exchange of materials.
–Cell growth is coordinated with
division.
–Cells that must be large have unique
shapes.
Chromosomes
• DNA plus proteins is
called chromatin.
• One half of a duplicated
chromosome is a
chromatid.
• Sister chromatids are
held together at the
centromere.
• Telomeres protect DNA
and do not include
genes.
• Chromosomes
condense at the start of
mitosis.
chromatid
telomere
centromere
telomere
Condensed, duplicated chromosome
• Cells divide during
mitosis and
cytokinesis.
• Mitosis and
cytokinesis produce
two genetically
identical daughter
cells.
– Interphase (G1, S, G2)
prepares the cell to
divide.
– During interphase, the
with
DNA is duplicated. nucleus
DNA
Parent cell
centrioles
spindle fibers
centrioles
4 Phases of Mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
• PMAT
Remember this…
Please Make A Taco
Prophase
• Chromatin condenses into
chromosomes (consisting
of two identical sister
chromatids).
• Nuclear envelope breaks
down
• Nucleolus disappears
• Centrosomes and
centrioles begin to move
to opposite sides of the
cell
• Spindle fibers form from
the centrioles
Interphase -> Prophase
Metaphase
• Spindle fibers
attach to the
centromere of
each
chromosome.
• Chromosomes
align along the cell
equater
• Meta=Middle
Prophase -> Metaphase
Anaphase
• Sister chromatids
separate from
each other.
• Spindle fibers
begin to shorten,
which pulls the
sister chromatids
away from each
other and toward
opposite sides of
the cell.
Metaphase -> Anaphase
Telophase
• Complete set of
identical
chromosomes is
positioned at each
pole of the cell.
• Nuclear membranes
start to form
• Chromosomes begin
to uncoil
• Spindle fibers fall
apart
Anaphase -> Telophase
Cytokinesis
• Divides the cytoplasm into
two daughter cells, each
with a genetically identical
nucleus
• Completion of one full stage
of the cell cycle
• Differs in animal and plant
cells
– In animal cells, cleavage
furrow forms pinching the
membrane closed.
– In plant cells, a cell plate
forms.
• Cells enter interphase and
the cylces begins again
Telophase -> Cytokinesis
Formation of New
Cells…
• Critical in both multicellular and
single-celled organisms
• Single-celled organisms use cell
division to reproduce
• Multicellular organisms use it for
growth, development, and repair.
Cell Cycle Book Directions
• Title Page: Your name
• Interphase: picture, description,
label…nucleus, chromatin, centrioles, and
spindle fibers
• Mitosis: definition
• Prophase: picture, description, label…nuclear
membrane, chromosomes, centrioles, and
spindle fibers
Cell Cycle Book Directions
• Metaphase: picture, description, label…
chromosomes, centrioles, and spindle fibers
• Anaphase: picture, description,
label…chromatid, centrioles, and spindle
fibers
• Telophase: picture, description, label…nuclear
membrane, chromatid, centrioles, and spindle
fibers
• Cytokinesis: picture, description,
label…nucleus, chromatin, and centrioles