Transcript Mitosis and the Cell Cycle

Cell Cycle:
Mitosis
How you got from one to trillions!!
Cell Cycle
• Interphase
•
•
•
•
Longest phase (94%)
G1: Cell growth
S: Replication of DNA
G2: Growth for division of cell
• Mitosis
• Division of nucleus and
chromosomes
• Cytokinesis
• Division of cytoplasm and
organelles into two daughter
cells.
Mitosis Cell Basics
• Somatic (body) cells.
• Diploid (2n): one
chromosome from
each parent. (n=23)
• Duplicated
chromosomes have 2
sister chromatids.
• Attached at
centromere in the
middle.
Both are called chromosomes!!
Mitosis
• Responsible for:
• Growth and replacement
• Repair
• Asexual Reproduction
Interphase
• Resting period.
• Nerve and muscle
cells rarely or don’t
divide.
• Cancer cells
continually divide.
• Most important: DNA
replication while
chromatin. S phase.
Interphase
Prophase
• 1st stage of mitosis
• Preparation
• Chromosomes condense.
• Nuclear membrane and
nucleolus disappear.
• Spindle forms: spindle
fibers from centrioles.
Prophase
Metaphase
• 2nd stage of mitosis
• Meet in the Middle.
• All chromosomes are lined
up at the middle, also
called the equator.
• Spindle fibers are attached
to the centromeres, one
from each centriole.
• Equal pulling from opposite
sides.
Metaphase
Anaphase
• 3rd stage of mitosis
• Moving away
• Centromeres split.
• Sister chromatids are
pulled to opposite poles
by spindle fibers.
• Each is now considered a
chromosome.
• Two diploid cells are
forming.
Anaphase
Telophase
• 4th stage of mitosis
• Two nuclei.
• Chromosomes change to
chromatin.
• Nuclear membrane
reforms.
• New nucleoli form.
• Cytokinesis is usually
happening at the same
time as telophase.
Telophase
Cytokinesis
• Cell membrane and cytoplasm
division.
• Plant cells have a cell plate that
forms between the new nuclei.
• Animal cells have a cleavage
furrow.
• Two new diploid daughter cells.
Video Quiz
• Let’s see how
well you know
your mitosis!!
Cell cycle signals
inactivated Cdk
• Cell cycle controls
 Cyclins
 regulatory proteins
 levels cycle in the cell
 Cdks
activated Cdk
 cyclin-dependent kinases
 phosphorylates cellular proteins
• activates or inactivates proteins
 Cdk-Cyclin complex
 triggers passage through different stages of cell
cycle
Cyclins & Cdks
1970s-80s | 2001
• Interaction of Cdk’s & different cyclins triggers the
stages of the cell cycle
Leland H. Hartwell
checkpoints
Tim Hunt
Cdks
Sir Paul Nurse
cyclins
Spindle checkpoint
G2 / M checkpoint
Chromosomes attached
at metaphase plate
• Replication completed
• DNA integrity
Active
Inactive
Inactive
Cdk / G2
cyclin (MPF)
M
Active
APC
C
cytokinesis
mitosis
G2
G1
S
MPF = Mitosis
Promoting Factor
APC = Anaphase
Promoting Complex
Cdk / G1
cyclin
Active
G1 / S checkpoint
Inactive
• Growth factors
• Nutritional state of cell
• Size of cell