You began life as a single
cell, and now you are
approximately 75 trillion
cells!
How did that happen?
Chapter 6 – Bio 1-2 Book (Blue)

The division of cells into more cells enables
living things to repair damage, to grow and to
produce offspring.


You are made of 75-100 Trillion Cells!
Your cells continually need to be replaced, they
wear out.
◦ Digestive Tract –
few days
◦ Immune system cells –
6 weeks
◦ Pancreatic Cells –
1 year

Binary Fission:
◦ Cell division in a
single celled
organism produces
two genetically
identical organisms.
Asexual
Reproduction
 Circular
Chromosome
See video
The nucleus!
What
are the 3
major reasons that
cells must
continue to divide?

Chromatin:

Chromosome:
◦ Chromatin made compact
for cell division.

Sister Chromatids:
◦ Two identical chromosomes
joined together.

Centromere:
◦ The region where two
chromatids join.
Chromosome
◦ DNA wrapped around
protein
Cells spend 90% of their time “living”
and growing.
 The period of growth between
divisions.
 DNA REPRODUCTION.

“INITIAL”

Mitosis is divided into
four phases:
◦
◦
◦
◦

Prophase
Metaphase
Anaphase
Telophase
New Cell Structures:
◦ Centrioles (animal only)
◦ Spindle Fibers


http://highered.mcgrawhill.com/sites/0072495855/student_view0/c
hapter2/animation__mitosis_and_cytokinesis.
html
Song:
http://www.youtube.com/watch?v=pOsAbTi9
tHw
 Prophase:
◦ 1st phase of mitosis
◦ Replicated
chromosomes
become visible.
◦ The nuclear envelope
breaks down and
spindle fibers begin
to form.
◦ A pair of centrioles
help to organize the
spindle fibers.
PREPARE

Metaphase:
◦ 2nd phase of mitosis
◦ Chromosomes line
up at the center of
the cell.
◦ Spindle fibers
connect to the
centromeres of
each chromosome
to the spindle.
MEET IN THE MIDDLE

Anaphase:
◦ 3rd phase of mitosis
◦ Centromeres split,
and the sister
chromatids
separate.
◦ A complete set of
chromosomes move
to the opposite
sides of the cell.
APART - AWAY

Telophase:
◦ 4th (final) phase of
mitosis
◦ Chromosomes
spread out into
chromatin.
◦ The nuclear
envelope reforms
around each group
of chromosomes.
◦ Spindles break
apart.
MAKES TWO
PLANT CELL

Mitosis produces two nuclei, each with a
complete set of chromosomes.
Cytokinesis completes the cell division by
splitting one cell into two daughter cells.
ANIMAL CELL

A
B
C
D



How do cells know when to divide?
Cells use proteins to regulate the cell cycle.
Some cells respond to outside signals:
◦ When one cell touches another they will stop
dividing.
◦ Used in healing.

Some cells use internal signals:
◦ Internal proteins regulate the timing of the cell
cycle. CHECK POINTS!






Cancer develops when the body loses the
ability to control growth in some of its cells.
Cancer forms a mass called a tumor.
Cancer cells can metastasize – or form
secondary growths elsewhere in the body.
Cancer cells are called malignant – meaning
they invade normal tissues.
Benign tumors are not cancerous. They do
not spread to other body parts or come back
after being removed.
See video
http://learn.genetics.utah.edu/content/health/history/cancer/