Download CELL CYCLE

CELL CYCLE
Mitosis
DNA
 In order for the DNA to fit inside the
nucleus, it must compact itself by coiling
 When DNA is unwound it is called
chromatin
 When the DNA is completely compacted
it is in the form of chromosomes
Cell Cycle
 Period from the beginning of one cell
division to the beginning of the next cell
division
 Divided into 2 parts:
 Interphase
 Cell Division
Interphase
 Occurs between cell divisions
 Cell prepares all the materials necessary for cell
growth and prepares it for division
 Accounts for 90% of the total time in the cell
cycle
 Divided into 3 stages:
 G1
 S
 G2
G1
 Also known as gap 1
 Characterized by growth and
development
S
 Also known as the synthesis phase
 Once the cell enters the S phase it is
committed to cell division
 Chromosomes in the nucleus replicate
G2
 Also known as gap 2
 Cell makes organelles and other
materials
 Centrioles replicate to form 2 pairs
Cell Division
 Splitting of one cell to form 2 cells
 Divided into 2 parts:
 Mitosis
 Cytokinesis
Mitosis
 Process during which a cell’s nucleus
divides into two identical nuclei
 It is divided into 4 phases:




Prophase
Metaphase
Anaphase
Telophase
Prophase
 Nucleus condenses
 Proteins form microtubules which form a fibrous
structure called the mitotic spindle
 Spindle stretches out between opposite poles of
the cell
 Nuclear envelope and nucleolus
break down
 Centromere attaches to spindle fibers
 Fibers move chromatids to center of
cell
Metaphase
 Chromosomes are pulled to center of cell
 Chromosomes line up on an imaginary line
called the metaphase plate
 ALIGNMENT IS CRUCIAL TO
ENSURE THAT EACH CELL
GETS A COMPLETE SET OF
CHROMOSOMES
Anaphase
 Centromeres divide
 Spindle fibers pull chromatids toward opposite
poles
 Chromatids are 2 identical sets of daughter
chromosomes
 Ends when chromosomes are at opposite ends
of the cell
Telophase
 2 daughter nuclei form
 Nuclear envelopes form around each set of
chromosomes
 Nucleoli appear
 Chromosomes uncoil to form chromatin
 Mitotic spindle disassembles
Cytokinesis
 Process in which the cell’s cytoplasm
divides to make 2 daughter cells
 Each daughter forms around 1 of the 2
nuclei produced during mitosis
Steps in Cytokinesis
 Begins during telophase
 The cell membrane, at the center of the cell,
folds inward to form a cleavage furrow
 The cell continues to pinch in half at the furrow
until the membrane meets and forms a division
resulting in 2 cells with complete cell
membranes