Download cell division - Lincoln Park High School

Bell Ringer
1. Why do cells need to divide in multicellular
organisms?
2. What is the difference between prokaryotes and
eukaryotes with regard to chromosomes?
3. What does a human chromosome consist of?
Draw one! Label.
4. Describe a role of chromatin in chromosome in
your own words.
DNA and Chromosomes
Chromatin
DN
A
The function of
chromatin is to
efficiently
package DNA
Histones
Cell Cycle
Cell Cycle is a sequence of events through
which a cell progresses during its lifetime
• Cell can be either in dividing (Mitotic
Phase) or non-dividing state (Interphase)
Interphase
about 90% of the cell cycle
G1 Phase (Gap 1):
•
•
•
•
Cell Growth
Protein Synthesis
Cell Metabolism
Preparation for S Phase
S Phase (synthesis):
– DNA is replicated
G2 Phase (Gap 2):
• Further Cell Growth
• Protein Synthesis
• Specialized
proteins needed for Cell Division
The cell grows during all three
phases, but chromosomes are
duplicated only during the S phase
Mitotic Phase
Mitosis:
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
is division of cytoplasm/cell:
– cleavage furrow forms in animal cells
– cell plate (cell wall) forms in plant cells
– daughter cells are identical
Figure 12.10a
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
100 m
Daughter cells
Figure 12.10b
(b) Cell plate formation in a plant cell (TEM)
Vesicles Wall of parent cell
forming
cell plate
Cell plate
1 m
New cell wall
Daughter cells
Cell Cycle
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis
Interphase
Animal Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Plant Cell
Prophase
Animal Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Plant Cell
Prophase
The cell prepares for nuclear division
• Animal and Plant Cell
– Packages DNA into
chromosomes
– nuclear envelope
breaks down
– Centrosomes move
apart and forms
spindle which guides
chr. separation
Metaphase
Animal Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Plant Cell
Metaphase
The cell prepares chromosomes for division
• Animal and Plant Cell
– Chromosomes line up at
the center of the cell
– Spindle fibers attach
from daughter cells to
chromosomes at the
centromere
Anaphase
Animal Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Plant Cell
Anaphase
The chromosomes divide
• Animal and Animal Cell
– Spindle fibers pull
chromosomes apart
– ½ of each chromosome
(called chromotid)
moves to each daughter
cell
Telophase
Animal Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Plant Cell
Telophase
The cytoplasm divides
• Animal Cell
–
–
–
–
–
chromosomes uncoil
2 nuclei form
spindle breaks down
nuclear envelope and
nucleoli reappear