Cell Cycle
Chapter 12~
The Cell Cycle
Cell Division: Key Roles
Genome: cell’s genetic information
Somatic (body cells) cells
Gametes (reproductive cells): sperm
and egg cells
Chromosomes: DNA molecules
Diploid (2n): 2 sets of chromosomes
Haploid (1n): 1 set of chromosomes
Chromatin: DNA-protein complex
Chromatids: replicated strands of a
chromosome
Centromere: narrowing “waist” of
sister chromatids
Mitosis: nuclear division
Cytokinesis: cytoplasm division
Meiosis: gamete cell division
Centromere Chromosome
Centriols
Spindle fibers
Sister
Chromotides
The Cell Cycle
Interphase (90% of cycle)
• G1 phase~ growth
• S phase~ synthesis of DNA
• G2 phase~ preparation for
cell division
Mitotic phase
• Mitosis~ nuclear division
• Cytokinesis~ cytoplasm
division
Mitosis
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Prophase
Chromosomes visible
Nucleoli disappear
Sister chromatids
Mitotic spindle forms
Centrosomes move
Metaphase
Centrosomes at
opposite poles
Centromeres are
aligned
Kinetochores of sister
chromatids attached
to microtubules
(spindle)
Anaphase
Paired centromeres
separate; sister
chromatids liberated
Chromosomes move
to opposite poles
Each pole now has a
complete set of
chromosomes
Telophase
Daughter nuclei form
Nuclear envelopes
arise
Chromatin becomes
less coiled
Two new nuclei
complete mitosis
Cytokinesis
Cytoplasmic division
Animals:
cleavage furrow
Plants:
cell plate
Why Division
The reasons that cells divide.
• The larger the cell the more demands the cell
places on its DNA.
• The second reason is it has a harder time
moving enough nutrients and wastes across
the membrane.
DNA doesn’t copy itself except for during
cell division
Cell Cycle regulation
Growth factors
Density-dependent
inhibition
Anchorage
dependence
Regulators
These help tell cells when to divide and
when to stop or to not divide at all.
These are proteins that regulate cell
division. They are called Cyclins.
There are 2 types of regulators internal and
external growth factors.
Cancer is uncontrolled cell growth.
Because it doesn’t respond to internal
growth factors or external growth factors
Internal growth factors- are proteins that respond to
events inside the cell.
• Like they don’t let it divide till all the chromosomes
have been copied
• Don’t let it go into anaphase until the spindle
fibers are attached
External growth factors- proteins that respond to
events outside the cell.
• Tell it to speed up or slow down the cell cycle
• Growth factors stimulate cell growth and division
of cells.
• Another are molecules found on the surface of
neighboring cells that tell the cell to slow down or
stop dividing
• These prevent excessive cell growth
Cancer
Transformation
Tumor: benign or malignant
Metastasis