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Cell Division and Reproduction Chapter 8.1 Why do cells go through cell division? • To grow – Organisms grow by ADDING more cells • To replace dead cells – All cells will die so they need to be replaced • To replace damaged cells – Cells will be damaged by injury (cut) Definition of Cell Division • Cell division is the process of one cell dividing into two identical daughter cells DNA - Hereditary Material • DNA is stored in a eukaryotic cells nucleus – Plant cells – Animal cells What is Chromatin? • Loose (stringy) DNA in a cells nucleus is called chromatin • DNA before cell division • DNA ‘hanging out’ Chromosome doubles • Chromatin condenses (shrinks up) and doubles just before cell division – This forms a chromosome (X). X X What is a Chromosome? • A chromosome is a structure made up of DNA and protein in the nucleus of a eukaryotic cell Cell Cycle • The cell cycle is the period of time from the beginning of one cell division to the beginning of the next. • The cell cycle has 3 parts: – Interphase – Mitosis – Cytokinesis See cycle on page 155 1. Interphase • First part of the cell cycle • Time in between cell divisions – Cell is on vacation • Longest phase. Most time is spent in interphase • At end, chromatin (stringy) doubles into a chromosome (X) Mitosis • Second part of the cell cycle • Makes 2 new identical nuclei • Has 4 steps: – Prophase – Metaphase – Anaphase – Telophase 2. Prophase • First step of mitosis • Chromatin in nucleus coils into chromosomes (X’s) • Nuclear membrane begins to disappear 3. Metaphase • Second step of mitosis • Chromosomes line up in the middle of the cell • Spindle fibers attach to the chromosomes 4. Anaphase • Third step of mitosis • Chromosomes separate and begin to move to opposite ends of the cell 5. Telophase • Final step of mitosis • Two new nuclei form around the separated chromosomes • Chromosomes unwind to form chromatin • Mitosis ends 6. Cytokinesis • • • • Final part of the cell cycle Makes 2 new identical daughter cells Shortest phase END of the cell cycle Cell Cycle • • • • • • Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Mitosis Cell Cycle Mnemonic • Write a mnemonic for cell division • (Ex. King Henry Died By Drinking Chocolate Milk.) • I • P • M Add a COLORED • A picture • T • C Cell Cycle Mnemonic • • • • • • I Played Music At The Concert
