Genetics Unit: Mitosis
How many stages of cell division
do you see in this image?
Cell Cycle
Mitosis will be
our main
focus.
First, we
will look at
Interphase…
)
Interphase
•
•
•
Longest stage of cell
division (90% of cell
cycle)
Nucleus is visible
Cell is growing and DNA
is being replicated.
)
Most
of
these
cells
are
Interphase:
3 Phases
in Interphase
1. G1: Cell is Growing
2. S: DNA is Synthesized
(DNA Replication)
3. G2: Organelles
duplicate in preparation
for division
)
Key Vocabulary
• DNA molecules are packaged
into chromosomes
.
– Human somatic cells (body
cells) have 46 chromosomes.
– Human gametes (sperm or eggs)
have 23 chromosomes.
• Chromosomes are made of a
material called chromatin
.
Key Vocabulary
• Chromatin is composed of DNA and
proteins
.
• It is supercoiled around proteins, called
.
histones
• Together the DNA and histone molecules
form bead-like structures called
nucleosomes
Key Vocabulary
• The chromosome is
duplicated.
• Each duplicated
chromosome consists
of two sister
chromatids
.
• These are connected
by a centromere .
Mitosis (M Phase)
The M Phase consists of:
• Mitosis and Cytokinesis
Four Stages of Mitosis:
• Prophase
• Metaphase
• Anaphase
• Telophase
For Homework: Left-side IntNB assignment: Write an Acrostic Poem for the four
stages of Mitosis
Preparing for Division
Late Interphase: G2
Centrosomes (with centriole pairs)
Nuclear membrane still visible
Nucleolus
Chromatin has been replicated
Preparing for Division
Late Interphase: G2
Early Spindle Apparatus
Prophase
Centromere
Nuclear
membrane
disappears
Chromosome consisting of two sister chromatids
Metaphase
Chromosomes line up at an
imaginary line between the
centrosomes at opposite ends
of the cell.
The spindle attaches to
the centromeres.
Anaphase
Spindles pull the
“daughter”
chromosomes appart
Telophase
Two nuclei become visible
In animal cells, a Cleavage
Furrow is visible
In plant cells, a cell plate is
now visible
Cytokinesis
The cytoplasm and
organelles divide.
Telophase & Cytokinesis
What’s the end product?
• Two identical daughter cells ready to start
the cycle again… or not.
• Some cells (like your nerve and muscle
cells) do not undergo division.
• For those that do (your skin and the lining
of your intestinal tract) how would you
know how quickly division takes place?