CELL CYCLE The events in the life of a cell

Interphase Interphase is the time between cell divisions where the cell grows to full size, duplicates its DNA and rests Cells live a “normal” life in Interphase Interphase is broken into three different sub-phases G1, (G0), S and G2

Interstate highway BETWEEN States

Cell Cycle Diagram.

G 1 Phase – (Gap) Occurs just after cell division Cell must re-grow to normal size Proteins are made

G 0 Phase – Resting Phase Most of an adult’s cells are in Interphase Cell undergoes normal cell functions while resting A cell that skips this phase can become cancerous, growing uncontrollably humorous animation

Check points Places where cell checks itself for damage before proceeding Cancer bypasses check points

S Phase - Synthesis DNA is synthesized or copied in preparation for cell division

Point of no return Once a cell enters this S phase it is committed to go through cell division A cell must divide or self destruct upon entering

G2 Phase – Gap 2 Cell grows larger in preparation for cell division Organelles, Centrosomes, enzymes and proteins are replicated

Cell Division The way a cell reproduces 2 phases: Mitosis followed by Cytokinesis

M Phase - Mitosis Division of cell Nucleus DNA forms into chromosomes Chromosomes separate with identical pairs moving to opposite sides of the cell New nucleus forms around each set of chromosomes

Chromosomes = colored bodies Only appear during Mitosis

Chromosomes Sister chromatids = identical DNA Homologous chromosomes = same type chromosome in pairs (paternal/maternal) Centromere – connects chromatids Kineticore – winds up spindle fibers to separate chromatids

Prophase Cell is beginning mitosis DNA coils up and Chromosomes appear Spindle fibers form Centrioles appear Chromosomes Centrioles Spindle fibers

Metaphase Chromosomes line up along center Centrioles migrate to poles Spindle fibers attach to chromatids

Anaphase Spindle fibers pull duplicate chromatids apart Chromatids migrate to opposite poles Chromatids

Telophase Chromotids gather together on separate sides Membrane forms around chromosomes making 2 separate nuclei Cell membrane begins to pinch together Nuclear membrane

Mitosis

C Phase – Cytokinesis Division of the cytoplasm between cells Membrane closes off each cell 2 new daughter cells form, each an identical copy of the original parent cell

Cytokinesis Plant vs Animal Animal - Cleavage furrow Plant – Cell Plate

Interphase (again) Each daughter cell enters interphase, so it can regrow, rest and be a normal cell

overview 24 hour cycle

Cell cycle animation

Binary Fission - Cell division in Prokaryotes NO nucleus No mitosis Origen of replication is where DNA replicated first

Regulation of the cell cycle Cyclin – a protein that controls the cell cycle CDK – (Cyclin Dependant Kinase) binds to cyclin to form MPF A Kinase is an enzyme that activates proteins MPF – (Maturation Promoting Factor) helps start M phase)

Formation of MPF brings past G 2 checkpoint

Control of cell cycle you tubeControl of cell cycle you tube video Control of the Cell Cycle

Growth factor Protein released by certain body cells that stimulate other cells to divide

Density-dependant inhibition Crowded cells stop dividing

Anchorage dependence To divide, most cells must be attached to a substratum

CANCER – Cells mutate and grow Normally a mutant cell is destroyed or self destructs. Called Apoptosis This does no occur in cancer cell Cancer cells are not inhibited by density or lack of anchorage

Tumors – Mass of abnormal cells Benign tumor – remains at original site Malignant tumor – becomes invasive and impairs function of other cells Metastasis – The spread of cancer cells