Transcript MITOSIS
CELL CYCLE The life cycle of a cell consists of a repeating set of events Phases of Cell Cycle • Interphase G1: Normal cell function S: DNA Replication G2: Preparation for cell division • M Phase (Red ) Mitosis Cytokinesis G1 Phase • Period of normal cell function • Cell growth and synthesis of materials needed for proper cell function take place • Certain cells never leave G1 Known as G0 Red blood cells, neurons, skeletal muscle cells These cells will not divide or grow, but will continue to function until cell death • Cells which will divide pass through a "point of no return" and proceed through S, G2 and mitosis. S Phase • DNA synthesis occurs. • Genes copy themselves by the process known as replication. Chromosomes consist of two identical strands once replication is completed. Each of these strands is called a chromatid. During mitosis the chromatids will separate and each chromatid will become a separate chromosome. M Phase • Mitosis: division of the nucleus Prophase Metaphase Anaphase Telophase • Cytokinesis: division of cell cytoplasm Animals—Cleavage Furow Plants—Cell plate Timing for a Typical Cell Cycle • Plants: usually 10-30 hours • Animals: 1824 hours • Varies from 20 minutes to several days or weeks • Greatest variation in G1 See Cell Cycle Animation Interphase • Most cells are in interphase, the phase between cell divisions. • The chromosomes are uncondensed with their strands existing as chromatin in the nucleus. They become condensed as chromosomes during mitosis. • Label- centrioles, chromatin, nucleus, MITOSIS • Mitosis: the nuclear division of a cell • Cytokinesis- produces two identical daughter cells. • Recognizable phases of mitosis: Prophase Metaphase Anaphase Telophase Early Prophase • Chromosome condensation – get thicker • Nuclear envelope breaks down • Centrioles move toward opposite poles and pulls the spindle fibers with them Late Prophase • Chromosomes very thick • Nuclear • Membrane disappears • The centromere attaches the chromosome to the spindle fibers. • Do NOT have to know kinetochore Metaphase • Chromosomes are aligned at the equator and are attached to the spindle. Anaphase • Individual chromatids pull apart.. Telophase and Cytokinesis Telophase • Chromosomes reach the poles • Nuclear envelope forms around each chromosome set Cytokinesis• Daughter cells become separated by cell membranes. Cytokinesis and Late Telophase • Chromosomes de-condense / get thinner • A nucleolus forms as the cells enter into interphase. Onion Root Tip: Interphase Onion Root Tip: Prophase Onion Root Tip: Metaphase Onion Root Tip: Anaphase Onion Root Tip: Telophase Interphase Prophase Prophase Metaphase Anaphase Telophase Telophase Which Stage is This?