Transcript Section 10.2 (Pg. 279-285): The Process of Cell Division

Section 10.2 (Pg. 279-285):
The Process of Cell Division
Eukaryote
Chromosomes
- Are genetic information bundled
into packages of DNA
- Make it possible to separate DNA
precisely during cell division
- Are packaged differently in
prokaryotes and eukaryotes
- Prokaryotes: small, circular
chromosome
- Eukaryotes: multiple chromosomes
Prokaryote
Eukaryotic Chromosomes
- Are made of chromatin
- DNA coils around proteins called histones
- DNA coiled around histones forms a unit
called a nucleosome
- Chromosome shape is supercoiled
chromatin
Prokaryotic Cell Cycle
- Prokaryotic cell division is called
binary fission
1) Cell grows and chromosome duplicates
2) Cell membrane pinches in
3) Cell divides into two daughter cells
Prokaryotic Cell
The Eukaryotic Cell Cycle
- Is when a cell grows, prepares for
cell division, then divides
- Is separated into two major parts:
1) Interphase
2) Cell division
- Interphase and cell division have
their own phases
Interphase
- Is the portion of a cell’s life in between
cell division
- G1 phase: Cell Growth
– Cell grows and performs normal functions
- S phase: DNA Synthesis
– DNA is copied for cell division
- G2 phase: Preparation for Cell Division
– Organelles and molecules are copied for cell
division
Cell Division
- Is also called M phase
- Contains the phases of cell division
- Mitosis
– Is the division of the nucleus
– Has 4 separate phases
- Cytokinesis
– Is the division of the cytoplasm
DNA During Cell Division
- Forms replicated chromosomes
– Each half of the chromosome is
called a sister chromatid
– They are held together by a
centromere
- Is separated into daughter
chromatids during cell division
Before Cell Division
- Cells are in interphase
– Nucleus is intact
– DNA has NOT yet formed
chromosomes
– Centrioles are lumped together near
the nucleus
Phases of Mitosis
1) Prophase
–
–
–
–
Replicated chromosomes condense
Nuclear envelope disappears
Nucleolus disappears
Centrioles move to the opposite sides of the
cell
– Mitotic spindle forms from centrioles
Phases of Mitosis
2) Metaphase
– Chromosomes attach to the spindles
and line up along the center
(midline) of the cell
Phases of Mitosis
3) Anaphase
– Sister chromatids separate and
move along the spindle fibers to
opposite ends of the cell
Phases of Mitosis
4) Telophase
– Nuclear envelope re-forms around
chromatids
– Nucleolus re-forms
– Chromatids uncoil into chromatin
– Spindle breaks apart
– Centrioles move near the re-forming
nuclei
Cytokinesis
- Completes cell division by splitting the cell
membrane and cytoplasm in two
- Different in animal and plant cells
– In animal cells the cell membrane pinches the
cell in two
– In plant cells a cellulose cell plate forms in
between the nuclei to make a cell wall