Cell Cycle

Chapter 12

Cell Cycle: 90% of Cell's life is spent in _____?

Interphase

Interphase phases

Gap 1 -- normal growth
Synthesis -- chromosomes duplicated
Gap 2 -- Cell duplicates organelles and produces proteins for mitosis

What happens in mitosis?

Division of nucleus and sorting + seperating of chromosomes

Purpose of Mitosis

Reproduction, Growth + Development, Tissue renewal

Where are Cell Cycle Checkpoints?

G₁ checkpoint, G₂ checkpoint, M checkpoint

What does G₁ Checkpoint check for?

Is the cell large enough to enter the cycle?

What does G₂ Checkpoint check for?

Have the chromosomes duplicated?
Checks for Cyclin: Cyclin + Cdk → MPF

What does the M checkpoint check for?

Are all dyads attached to spindlefibers?

Phases of Mitosis

Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis*
*happens with the latter stages of mitosis. NOT part of mitosis.

Interphase

Cell has made preparations for division.

Prophase

Chromatin condense + visible
Spindle fibers synthesized
Nuclear membrane begins to dissolve

Prometaphase

Nuclear membrane dissolved
Centrosome almost at opposite poles
Kinetochore microtubules (spindle fibers) attach to dyads

Metaphase

Kinetochore microtubules push dyads to metaphase plate
Non kinetochore microtubules (also spindle fibers) grow + overlap

Anaphase

Monads migrate to opposite poles
use reeling model or pac man model

Reeling Method

Motor proteins pull on microtubules from centrosome end, Enzymes dissolve microtubules at centrosome end

Pac-Man method

Enzymes would dissolve microtubules from kinetochore end, while motor proteins "walk" the monat

Telophase

New nuclei membranes
Monads decondense
Microtubule breakdown

Cytokinesis (animal)

Contractile microfilaments made inside plasma membrane
initial contraction = cleavage furrow

Cytokinesis (plants)

Build new cell walls to divide daughter cells

Plant mitosis vs animal mitosis

Plants mitosis in meristem rapidly dividing areas to elongate tips of stem/root or expand width)
Animal mitosis throughout body

Plant cytoplasmic division = build cell wall
Animal cytoplasmic division - cleavage furrow