Cell Divison & Regulation

Interphase

G1, Synthesis, G2, G₀ (cells spend 90% of their time in this group of phases)

Gap 1 (G1)

Growth, protein synthesis, organelle synthesis

Synthesis (S)

DNA is duplicated

Gap 2 (G2)

Growth, synthesis of microtubules, cell cycle checkpoints

G₀

Resting state (quiescent), cells NOT preparing to divide but are still metabolically active (majority of cells reside in this state)

Mitosis

Nuclear division, produces 2 identical daughter cells, composed of 5 phases

Prophase

Chromosomes begin to condense, spindle apparatus begins to form

Prometaphase

Nuclear envelope disassembles, spindle fibers attach to kinetochores

Metaphase

Chromosomes align along metaphase plate, this occurs due to a pull on the chromosomes that comes from the poles at the ends of the cell

Anaphase

Sister chromatids are pulled apart and to opposite poles (this is achieved through the shortening of microtubues)

Metaphase Plate

An imaginary line that goes down the center of the cell

Sister Chromatids

Created through duplication of chromosomes, made BEFORE cell division begins, held together at centromere

Cohesin

Protein that holds sister chromatids together, gets cleaved by enzymes during anaphase

Telophase

Reversal of prophase, nuclear envelope reforms around DNA, chromosomes unfold back into chromatin

Cytokinesis

Division of cytoplasm, begins DURING telophase, NOT a part of mitosis

Animal Cytokinesis

Cleavage furrow pinches of separated nuclei to produce 2 separate cells

Plant Cytokinesis

New cell wall forms producing 2 separate cells

Cell-Cycle Clock (Cyclin)

Molecules dependant on kinases (CDKs), always present but usually inactive

G1 Checkpoint

Most important checkpoint in mammals, green light = continuation into S phase, red light = exits cell cycle and enters G₀

M-Phase Promoting Factor (MPF)

G2 checkpoint, protein dimer consists of cyclin and CDKs, targets: condensins, proteins involved in mitotic spindle formation, lamins

Anaphase Promoting Complex (APC)

M-Phase checkpoint, complex of 11-13 proteins that mark cell cycle proteins for degredation

External Regulation Factors

Growth factors, density-dependant inhibition, anchorage dependance