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The Tragic Ending
Cell Division in Eukaryotes
• As you are sitting in class now, your
cells are growing, dividing and dying.
Cuts and bruises are healing
Muscle cells are
get larger when
you exercise.
RBC’s are being
produced in your
bones at a rate of
10-15 million per sec.
Worn out cells in the palm of your hand are being replaced.
Cell Division
How do you grow?
The number of cells in your body is increasing!!
How Do Cells Increase In
Number?
• In your body, all of your cells, except your
sex cells, divide by a process called mitosis.
• In mitosis, a parent cell divides to form two
identical daughter cells.
• The daughter cells have the same contents
of the parent’s nucleus.
Cell Cycle
• Most of a eukaryotic cell’s life is
spent in a phase called interphase.
• Interphase consists of three stages: G1, S,
and G2
– G1: a time of growth and maintenance
– S: DNA is replicated: this commits the
cell to divide
– G2: more growth as the cell prepares
for division
Cell Cycle
• Mitosis: division of the
nucleus:
– Four phases: prophase,
metaphase, anaphase and
telephase.
• Cytokinesis: division
of the cytoplasm
• After the cell divides
into 2 identical daughter
cells, the cycle starts
over again.
http://www.cellsalive.com/cell_cycle.htm
Cell Cycle
Interphase
• Chromatin coils up into chromosomes
• A copy of each chromosome in the nucleus is
produced
• These duplicated chromosomes are held
together by a centromere.
• Cells that no longer divide are always in
interphase.
Interphase
Mitosis in Animal Cells
• A form of asexual
reproduction
• The nucleus of a cell
divides, producing 2
nuclei that are
identical to each
other
• Has 4 phases:
prophase, metaphase,
anaphase, telophase
Prophase
• Duplicated chromosomes become fully visible
• Organelles called centrioles move to opposite ends of
the cell
• The nucleolus and nuclear membrane disintegrate
• Threadlike spindles stretch across the cell between
the centrioles
Prophase
Metaphase
• Duplicated chromosomes line up across the
center, or equator, of the cell.
• Each centromere attaches to 2 spindle fibers
Metaphase
Anaphase
• Each centromere splits and the identical
chromosomes separate and move towards
opposite ends of the cell.
Anaphase
Telophase
• Spindle fibers disappear
• Chromosomes uncoil and are harder to see
• A nuclear membrane forms around each mass
of chromosomes
• A new nucleolus forms in each new nucleus
Telophase
Cytokinesis
• The cytoplasm and its contents divide
into 2 individual daughter cells.
• Each daughter contains a nucleus and
identical chromosomes.
Virtual Lab
• Cell Reproduction
• http://bio.rutgers.edu/~gb101/virtuallabs_10
1.html
Mitosis in Plant Cells
• What’s Different?
• Plant Cells do not have centrioles
• A cell plate forms between 2 new nuclei
• New cell walls form along the cell plate, and
new cell membranes form inside the cell walls.
Plant Mitosis
"And do you, Michelle, take Andrew
until mitosis do you part?"
Chromosomes
-The 22
autosomes are
numbered by size.
-The
other two chromosomes, X
and Y, are the sex chromosomes.
The above picture of the human
chromosomes lined up in pairs is
called a karyotype.