the beginning of one cell division to the beginning of the next. ⢠The cell cycle has 3 parts: â Interphase. See cycle on page 155. â Mitosis. â...
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 diving 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 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
