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