Cell Cycle and Mitosis Student PDF

CELL CYCLE AND CELL REPRODUCTION Honors Biology Framingham High School  CELL REPRODUCTION IN PROKARYOTES Binary fission: DNA is copied, cell splits in two. Most bacteria are always ready to divide, with multiple copies of their chromosome r...

CELL CYCLE AND CELL REPRODUCTION Honors Biology Framingham High School  CELL REPRODUCTION IN PROKARYOTES Binary fission: DNA is copied, cell splits in two. Most bacteria are always ready to divide, with multiple copies of their chromosome ready made. Reproduction can be very fast. (20 min for E. coli, 16-18 min in Salmonella enterica serovars.) CELL DIVISION IN EUKARYOTES C E L L C YC L E MITOSIS & CYTOKINESIS  G1 phase: growth phase 1. Cell grows to THE CELL CYCLE adult size and begins performing any specialized tasks. At the G1 checkpoint, the cell will go into either: Mitosis & cytokinesis G0 phase: the cell no longer grows and G1 does not divide. It continues to do its tasks. G2 S phase: synthesis phase. The cell makes a copy of all DNA molecules. S G2 phase: growth phase 2. The cell begins to stockpile ATP, store food, etc. so that it can divide.  CELL REPRODUCTION IN EUKARYOTES DNA is copied at S phase before mitosis  Mitosis: division of the nucleus Prophase & Prometaphase Metaphase Anaphase Telophase  Cytokinesis: division of the cell The parent cell splits into two daughter cells.  PROPHASE & PROMETAPHASE Chromosomes condense Centrioles move to opposite sides of cell Aster (spindle) fibers form from centrioles Nuclear membrane disappears (—prometaphase)  DNA PACKAGING 2 meters (6’) of DNA in each cell —must be heavily compacted to fit in nucleus DNA is wrapped around histone proteins Histones then stick together  METAPHASE Microtubules anchored on centrioles push and pull chromosomes Chromosomes align along center of cell Chromosomes moved by motor proteins walking down the microtubules (aster fibres) Microtubules are lengthened and/or shortened which push away or pull towards the centrioles  ANAPHASE Centromere breaks and chromatids are pulled apart Motor proteins “walk” the chroma- tids down the microtubules, which are also disassembled  TELOPHASE Nuclear membranes begin to form around the DNA at each end of the cell; results in two nuclei The cell starts to go through cytokinesis  CYTOKINESIS “Cell Splitting” A ring of protein forms around equator of cell The ring gradually contracts , splitting the cell in two Cleavage furrow  MITOSIS & CYTOKINESIS ANIMATION & VIDEO See the Canvas site for the animations. MITOSIS & CYTOKINESIS SUMMARY  Cell is in anaphase XENOPUS (FROG) XLK2 CELL (100X) H. SAPIENS CELLS (1000X) CANCER  DISEASE OF THE CELL CYCLE: CANCER Cancer: mutant cells undergo continuous division (cell cycle proceeds without stopping: no G0) Large masses of fast-growing cells form tumors. The primary tumor Beagle with a tumor is the mass of cells from the initial mutant. Cancer cells can metastasize (break away) from the primary tumor & spread to other parts of the body, CT scan showing brain tumor Mammogram showing forming secondary tumors. a tumor  GETTING CANCER Cancer is caused by genetic mutations that lead to uncontrolled cell reproduction. Multi-hit hypothesis: many specific mutations in the same cell are required to develop cancer. (One mutation is not enough) Mutation that tells the cell to divide when it shouldn’t Mutation that blocks apoptosis Mutation that stops contact inhibition Mutation that damages the ECM (to metastasize.  FACTORS THAT CAN INCREASE THE RISK FOR CANCER Environmental factors Genetics Anything that can cause It is possible to inherit some mutations in your DNA can cancer-causing mutations from cause cancer your ancestors. This increases chemicals your risk because you do not radiation need to acquire as many over Viruses the course of your life. Because mutations are rare and accrue slowly, cancer is usually only seen late in life.  TREATING CANCER Surgical excision Primary tumors must be excised; very successful unless part of tumor remains, or tumor has metastasized Chemotherapy Drugs that interfere with mitosis; affects any rapidly dividing cells Serious side effects as normal fast dividing cells killed Radiation therapy Ionizing radiation aimed at or inserted into tumor Problems with targeting; collateral damage Immunotherapy