Transcript 113704_Mitosis_Intro.pptx

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. 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
– cells have biochemical needs proportional to
their size, and the membrane is the means by
which things move in and out - and the cell
membrane grows more slowly than the
volume as cell size increases.
Why do cells need to divide?
• The work of the cell occurs at the boundaries –
cells have biochemical needs proportional to
their size, and the membrane is the means by
which things move in and out - and the cell
membrane grows more slowly than the volume
as cell size increases.
• What if Anchorage doubled in size but it didn’t
add new roads, airports, or ports at a
proportional rate? 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.
• Nuclear 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 – a new cell wall is built
between the two new daughter cells)
Cytokinesis