Cell Growth and Division
• The human body forms two types of cells, body
cells and sex cells.
• You produce more body cells than sex cells
Why do cells divide?
• For reproduction
– asexual reproduction
• one-celled organisms with
same DNA as parent.
• For growth
– from fertilized egg to
multi-celled organism
• For repair & renewal
– Regeneration is when a
body part regrows and may
form a new organism.
amoeba
Cell cycle
M
Mitosis
G2
Gap 2
• Cell has a “life cycle”
• Broken down into steps
cell is formed from
a mitotic division
cell grows & matures
to divide again
G1, S, G2, M
epithelial cells,
blood cells,
stem cells
S
Synthesis
cell grows & matures
to never divide again
liver cells
G1G0
brain / nerve cells
muscle cells
G1
Gap 1
G0
Resting
Interphase
First step of the Cell Cycle
• Divided into 3 phases:
– G1 = 1st Gap (Growth)
• cell doing its “everyday job”
• cell grows
– S = DNA Synthesis
• copies chromosomes
– G2 = 2nd Gap (Growth)
• prepares for division
• cell grows (more)
• produces organelles,
proteins, membranes
Interphase
•
During this phase, cells go
through periods: rapid growth,
DNA synthesis.
•
Cells spend the majority of their
time in interphase.
•
Nucleus well-defined
– DNA loosely packed in long
chromatin fibers
•
Chromosomes are structures that contain DNA, that
determine what traits a living thing will have.
•
•
•
•
During cell division each chromosome has to make an exact copy
of itself.
During Interphase, you can’t see chromosomes.
As the cell prepares to divide the chromosomes become compact
and visible.
Centromere: is found in the center of the
Chromosomes.
Cell Cycle
Interphase
On the back: write and answer the questions:
What type of cells go through all four steps of the cell cycle (G1, S, G2, M)?
What type of cells don’t divide?
Chromosomes
Mitosis
Second step of the Cell Cycle
• Dividing cell’s DNA between
2 daughter nuclei
• 4 phases
– prophase
– metaphase
– anaphase
– telophase
green = key features
Prophase
• Chromatin condenses to form visible
chromosomes
• Centrioles (are organelles that help the
cell divide) move to opposite poles of
cell
• Microtubules come from the centrioles
to form mitotic spindle
– Helps coordinates movement of
chromosomes
• Nucleolus disappears
• Nuclear membrane breaks down
Prophase “pasta”
green = key features
Metaphase
• Chromosomes align along
middle of cell
• meta = middle
– spindle fibers coordinate
movement
Metaphase
green = key features
Anaphase
• Sister chromatids separate
– move to opposite poles
– pulled at centromeres
• increased production of
ATP by mitochondria
• Poles move farther apart
Anaphase
green = key features
Telophase
• Chromosomes arrive at
opposite poles
– daughter nuclei form
– nucleoli form
– chromosomes disperse
• no longer visible under
light microscope
• Spindle fibers disperse
• Cytokinesis begins
– cell division
Telophase
Cytokinesis in Animals
• Animals
– constriction belt of actin
microfilaments around
equator of cell
• cleavage furrow forms
• splits cell in two
– Cytoplasm pinches off
Cytokinesis in Plants
• Plants
– Since they have a cell
wall, the cleavage furrow
would not work instead a
cell plate forms, which
helps to make a new cell
wall and new cell
membrane
Results of Mitosis
• The division of the nucleus
• Two new cells that have the same number
of chromosomes as the original cell.
Overview of Cell Cycle
interphase
prophase
I.P.M.A.T.
(pro-metaphase)
cytokinesis
metaphase
anaphase
telophase
Mitosis in whitefish blastula
Mitosis in animal cells
Mitosis in plant cell
onion root tip
metaphase
anaphase
Tumors
• Tumor: is a mass of abnormal cells that
develops when cancerous cells divide and
grow uncontrollable
2 types:
1. Benign Tumors: are non cancerous tumors
2. Malignant Tumors: are cancerous tumors
Cancer
• There are over 200
types of cancers
• Occurs in almost any
part of the body.
• Are named by the
place in the body
where they begin.
Treating and Preventing Cancer
• Treatment
– Surgery
• Usually the best treatment because they can completely
remove the tumor.
– Radiation
• Consists of beams of high-energy waves.
– Chemotherapy
• Is the use of drugs to treat a disease, which is carried
throughout the body through the bloodstream
• Preventing
– Avoid smoking
– Eating health diet
– Protect their skin from bright sunlight