Cell Cycle, Mitosis, Cell Cycle Regulation PDF

THE CELL CYCLE Vocabulary Cell cycle- An orderly set of stages that take place during the cell’s life Can be split up into two parts: interphase and M phase  INTERPHASE Vocabulary Interphase- the phase of the cell cycle where the cell pr...

THE CELL CYCLE Vocabulary Cell cycle- An orderly set of stages that take place during the cell’s life Can be split up into two parts: interphase and M phase  INTERPHASE Vocabulary Interphase- the phase of the cell cycle where the cell prepares to divide, while also doing its normal functions in the body. Adult cells spend ~20 hrs per day in interphase Embryonic cells ~3 hrs per day in interphase Consists of 3 stages (G1, S, and G2)  G1 STAGE PART OF CELL CYCLE: INTERPHASE Recovers from the previous division, increases in size, and duplicates organelles. Still doing daily functions. G0 Stage occurs if the cell is not ready for S Phase (like a pause button)  S STAGE PART OF CELL CYCLE: INTERPHASE The process of DNA replication creates an identical copy of each DNA strand (chromatid) The two ”sister” chromatids will stay attached until mitosis Chromosome: :thread”, tightly coiled strands of DNA.  G2 STAGE PART OF CELL CYCLE: INTERPHASE Further cell growth occurs to prepare the cell for division (mitosis) Example: builds proteins needed for M phase  M (MITOTIC) PHASE Vocabulary: M Phase: the phase of the cell cycle where a single cell splits into two new cells. Purpose: growth and repair Includes Mitosis (division of the nucleus) and Cytokinesis (division of the cytoplasm)  PHASES OF MITOSIS Mitosis can be split into four phases: Prophase Metaphase Anaphase PMAT Telophase  PROPHASE PART OF CELL CYCLE: M PHASE Events: DNA condenses (squeezes together) into chromosomes Nucleus starts to disappear, nuclear envelope fragments Mitotic spindle starts to be built  PROPHASE PART OF CELL CYCLE: M PHASE Vocabulary: Histones: Proteins that help organize chromosomes Chromatin: loosely coiled DNA Chromosomes: tightly packed DNA Mitotic spindle: “molecular machine” that pulls chromosomes apart to make two daughter cells CHROMATIN AND CHROMOSOMES  METAPHASE PART OF CELL CYCLE: M PHASE Events: Centromeres of the chromosomes are pulled to the middle of the cell by the mitotic spindle. Metaphase plate - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - -- - - - - - - - - Longest phase- next phase can’t start Centromere until chromosomes are properly attached and positioned “M” for metaphase, “M” for middle  ANAPHASE PART OF CELL CYCLE: M PHASE Events: The two sister chromatids split at the centromere, becoming two daughter chromosomes Daughter chromosomes are pulled to opposite poles Shortest phase “A” for anaphase, “A” for apart  TELOPHASE PART OF CELL CYCLE: M PHASE Events: Mitotic spindle is broken down New nuclei form around both sets of daughter chromosomes Chromosomes decondense into chromatin  CYTOKINESIS PART OF CELL CYCLE: M PHASE The division of the cytoplasm to make two separate cells, usually starts during anaphase Animal Cells Cleavage furrow (indention of the membrane) pinches cell apart Plant Cells Building of a new cell wall between the daughter cells  Many of you will start driving soon. What are some things that you need to do to be allowed to drive. What are some things that you need to do to be safe when you get into a car? Driving a car is a regulated process, much like cell division. If cells divided out of control, what would happen?  CELL CYCLE REGULATION The cell cycle is regulated to make sure that cells divide in a controlled fashion. There isn’t infinite room for cells in the body, so cells should only divide when the body is growing, or to replace damaged cells.  CELL CYCLE REGULATION A checkpoint is a stage in the cell cycle where the cell checks certain signals and "decides" whether to go on with division. There are several checkpoints, but the most important are: G1 checkpoint, between G1 and S (makes sure cell is large enough, checks for growth signals) G2 checkpoint, between G2 and M (makes sure DNA is replicated and not damaged) M checkpoint, between metaphase and anaphase (makes sure chromosomes are attached to spindle fibers)  CELL CYCLE REGULATION What if the cell fails the checkpoint? If what’s wrong with the cell can be fixed, then the cell cycle can pause (the cell may go into G0 phase). If what’s wrong cannot be fixed (usually DNA damage), the cell will undergo apoptosis.  APOPTOSIS Apoptosis: Cell self-destruct Checkpoints signal a cell to go through apoptosis if it is too damaged to fix If damaged cells are allowed to divide, they will pass on that damage to their daughter cells, creating cells that don’t do normal body functions.  MUTATIONS Normally, proteins called regulators control the cell cycle and the checkpoints, giving the cell signals on what to do. For example, growth factors encourage a cell to grow and divide. If a cell develops a mutation that changes its regulators, it can start dividing out of control. That cell will pass on DNA damage with every division, creating a group of nonfunctional cells that divide out of control. These will be cancer cells.  MUTATIONS Mutations: Heritable (able to be inherited) changes in genetic information. 2 Types: Gene Mutations (Only in a single gene) Chromosomal Mutations (Whole chromosome) If a mutation results in a change to the cell cycle, this causes a tumor.