The events in the life of a cell CELL CYCLE The events in the life of a cell
Interphase 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 .
G1 Phase – (Gap) Occurs just after cell division Cell must re-grow to normal size Proteins are made
Cyklins mediate process
G0 Phase – Resting Phase Most of an adult’s cells are in Interphase, stopping in G0 Cell undergoes normal cell functions while resting A cell that skips this phase can become cancerous, growing uncontrollably Humourous cell cycle video 3.5 mins
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
M Phase - Mitosis Division of cell Nucleus DNA forms into chromosomes Chromosomes separate with identical pairs moving to opposite sides of the cell New nuclear membrane 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
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 G2 checkpoint
Control of the Cell Cycle Control of cell cycle you tube video
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 something
CANCER – Cells mutate and grow Normally a mutant cell is destroyed or self destructs. Called Apoptosis This does not 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
Interphase (again) Each daughter cell enters interphase, so it can regrow, rest and be a normal cell
Mitosis
Interphase The non dividing portion of the cell cycle Most of the time a cell is in interphase
Prophase Chromosomes become visible Spindle fibers form Nuclear envelope breaks down Centrioles are replicated (Animal cells only)
Metaphase Chromosomes are aligned at the metaphase plate. Polar microtubules vs. Kinetochore microtubules.
Anaphase Each Kinetochore “eats” the spindle fiber and the sister chromatids are moved apart. The polar microtubules push the poles apart.
Telophase The nucleus reforms The chromosomes become chromatin Cytokinesis begins
CytoKinesis The complete separation of daughter cells. Membrane sides connect
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
Onion cell mitosis
Animal cells Interphase Prophase Metaphase Anaphase Telophase
Plant cells Prophase Anaphase Metaphase Interphase Telophase
Metaphase Interphase Prophase Cytokinesis Anaphase interphase