Transcript Cell Division12-13 - McKinney ISD Staff Sites

Cell Division
Chapter 10
Anatomy of a
Chromosome
coils of DNA and proteins
Centromerewhere the
two
chromatids
attach
Chromatid- two exact copies of DNA that make up a chromosome
Limits to Cell Growth
• DNA Overload
– The larger a cell becomes, the more demands
the cell places on its DNA
• Exchanging Material
– The cell has trouble moving enough nutrients
and wastes across the cell membrane if the
cell is too big.
– Surface Area:Volume ratio can’t be too small
Cell Cycle
• Interphase (inter- means “between”)
– G1 phase – Cell growth
– S phase – DNA replication
– G2 phase – preparation for cell division
– Cells are in interphase most of the time.
• M phase
– Mitosis: prophase, metaphase, anaphase,
telophase, cytokinesis
• G0 phase
– Cells that cannot divide like nerve cells, red
blood cells, and cardiac cells
Prophase
A?
• What are the important
events happening during
Prophase?
Plant cells in prophase
Pair of centrioles
B?
C?
D?
Plant cells in prophase
Prophase
• Chromosomes condense
into sister chromatids
• Chromatids are joined by a
centromere
• Centrioles appear and form
mitotic spindle
• Nucleolus disappears and
nuclear envelope dissolves
• Longest phase of mitosis
(50-60%)
Pair of centrioles
Metaphase
Animal cell
Plant cell
A?
B?
C?
D?
• What events are occurring during
Metaphase?
Metaphase
Animal cell
Plant cell
• Centrioles on opposite ends of the cell
• Microtubules of mitotic spindle attach to
the centromeres
• Chromosomes line up across the middle
(equator) of the cell
Anaphase
• What
important
events are
occurring at
Anaphase?
A?
B?
Early anaphase (plant)
C?
D?
Anaphase (animal)
Late anaphase (plant)
Anaphase
Early anaphase (plant)
• Sister chromatids separate
• Chromosomes migrate to
opposite ends of the cell
Anaphase (animal)
Late anaphase (plant)
Telophase
Plant cell
Animal cell
• What important events happen during
Telophase?
A?
B?
C?
D?
Telophase
Plant cell
Animal cell
• Chromosomes begin to disperse
• Nuclear envelopes reform
• Mitotic spindle breaks apart
Animal cell
Cytokinesis
Plant cell
• Difficult to distinguish from telophase
• In animal cells the cell membrane pinches in
forming two daughter cells
• In plant cells a cell plate forms between the
daughter nuclei and a new cell wall forms at
the cell plate
Which stage is each photo in??
How do
you
know??
Now its YOUR turn! 
What are the important events at each
phase?
G1 phase –??
S phase –??
G2 phase –??
What types of cells would be in
G0 phase??
Cancer
• Uncontrolled cell growth
– Caused by smoking, exposure to radiation or
certain chemicals, some viruses
• Cancer cells smother normal cells
• Treatment options
– Surgery to remove tumor
– Radiation therapy to halt cell division
– Chemotherapy to halt cell division