Mitosis (cell division)
O…M…G…. More notes? Sweet! I’m telling you, Captain Science,
there is nothing I would rather do than take notes on a Monday
morning. I was thinking the best thing about today was going to
be food, but this is soooo much better. Well…except for chocolate.
It’s not quite as good as that, but close. (It’s definitely better than
white chocolate, but that’s not really chocolate anyhow. It’s just
yogurt pretending to be chocolate. Gross. And speaking of
chocolate, Mr. Mason likes dark chocolate. Just FYI.)
Anyhow…yeah! Notes! Woohoo!!!
Why do cells need to divide?
Why do cells need to divide?
• The work of the cell occurs at the boundaries.
Why do cells need to divide?
• The work of the cell occurs at the boundaries.
• What if Anchorage doubled in size but it didn’t
add any new roads, airports, or ports? What if
it tripled in size?
Mitosis
• Mitosis – The process of cell replication in
somatic (body) cells
The Cell Cycle
Interphase
• Cell spends the majority of life in interphase
Interphase
• Cell spends the majority of life in interphase
– G1: Cells grow to mature size (growth phase)
Interphase
• Cell spends the majority of life in interphase
– G1: Cells grow to mature size (growth phase)
– S: Cell’s DNA is copied (synthesis phase)
Interphase
• Cell spends the majority of life in interphase
– G1: Cells grow to mature size (growth phase)
– S: Cell’s DNA is copied (synthesis phase)
– G2: Cell prepares for division
Interphase
• Cell spends the majority of life in interphase
– G1: Cells grow to mature size (growth phase)
– S: Cell’s DNA is copied (synthesis phase)
– G2: Cell prepares for division
– G0: ???
Interphase
• Cell spends the majority of life in interphase
– G1: Cells grow to mature size (growth phase)
– S: Cell’s DNA is copied (synthesis phase)
– G2: Cell prepares for division
– G0: Cell exits cell cycle. Cells are not copying DNA
or preparing to divide. (The vast majority of the
body’s cells are in G0 , simply doing their job
instead of preparing to divide.)
Mitosis
• Mitosis – The actual process of division,
broken into 5 steps:
– Prophase
– Metaphase
– Anaphase
– Telophase
– Cytokinesis
1. Prophase
• Chromatin (loose, uncoiled DNA) coils into
tightly wound chromosomes
• Sister chromatids (identical copies of
chromosomes) held together by a centromere.
• Nulear membrane breaks down and
disappears.
• Centrioles move to opposite poles and spindle
fibers start to extend.
Prophase
2. Metaphase
• Chromosomes move to the equator of the cell
• Spindle fibers connect to chromosomes at the
centromere
3. Anaphase
• The sister chromatids separate and move
towards the opposite poles, pulled by
shortening spindle fibers
4. Telophase
•
•
•
•
Chromatids reach the opposite ends of cell
Mitotic spindle disappears
Chromosomes start to uncoil into chromatin
Nuclear envelope starts to reform
Telophase
Cytokinesis
• Cell membrane pinches inward at the cleavage
furrow*, eventually splitting the one original
cell into two daughter cells (*no furrow
evident in plant cells)
Cytokinesis