Chapter 4 Section 3
Mitosis
The Cell Cycle
 Your
body produces millions of
cells in order for you to grow
and to replace cells that have
died
 Ex. Stomach lining is replaced
every few days
The Life of a Cell
 Cell
Cycle
The
life cycle of a cell
 Begins
when the cell is formed
and ends when the cell divides
and forms new cells
Before a cell divides
 It must first make a copy of its
DNA
 DNA contains the information
that tells a cell how to make
proteins.
 DNA is organized into
chromosomes
Making More Prokaryotic Cells
 Prokaryotic cells and their
DNA are relatively simple
 Bacteria have ribosomes and
a single circular molecule of
DNA
 Therefore division for bacteria
is simple
Binary Fission
 Splitting
into 2 parts
 Each resulting cells contain
one copy of the DNA
Binary Fission

http://diverge.hunter.cuny.edu/~weigang/Images/06-11_binaryfission_1.jpg
Eukaryotic Cells and Their DNA
 Larger
and more complex than
prokaryotic cells
 Because of this, eukaryotic
cells have MORE DNA
 Chromosomes contain DNA
and Proteins
Eukaryotic Cells
Number
of chromosomes
differs from one kind of
organism to the next
Number has nothing to do
with the complexity of the
organism
 Fruit
Fly- 8 chromosomes
 Potato- 48 chromosomes
 Humans- 46 chromosomes
Homologous Chromosomes
 Chromosomes
information
 Pairs
with matching
Making More Eukaryotic Cells
3
main stages of cell cycle
 Stage 1 or Interphase - cell
grows and copies its
organelles and chromosomes,
DNA and protein strands are
loosely coiled pieces of thread
Interphase continued
 After
the chromosomes are
duplicated, the two copies are
called CHROMOTIDS which
are held together at a region
called a CENTROMERE
 Chromatids coil and condense
into an X shape
Mitosis, Stage 2
 Chromatids
separate
 Mitosis – process of
chromosome separation
Two
 Each
new nuclei are made
new cell receives a copy
of each chromosome
Stage 3 of Cell Cycle
 Cytokinesis
 The
cell divides and produces
2 new cells that are identical to
the original cell