Download What are Chromosomes

Why do you look like your parents?
Why do twins look alike?
We inherit our parent’s traits.
What makes heredity possible?
Soon after microscopes were
developed, scientists suspected
that it was something in the nuclei
of our cells!
When a cell is about to divide,
something happens in the
nucleus.
Chromosomes appear!
They line up
Then they separate
It happens in animal cells
And plant cells
Line up
Separate
What’s going on?
Something in the chromosomes is
so important
that each new cell needs a copy of it!
What are Chromosomes ?
The electron microscope reveals
a chromosome is a coiled up thread.
Coils and coils
of DNA.
Before a cell can divide,
the nucleus must divide
In Humans, there are 46 long strands of DNA in that
nucleus, looking like 46 fishing lines all cast out at once.
How could they be separated without getting
tangled and broken?
What is RULE #1 if someone hooks a fish
when a group is fishing from a boat?
Reel in your line!
Chromosomes are
reeled in DNA!
The process of reeling in
the DNA, lining up the
duplicate reels
(chromosomes)
and making sure each
new nucleus gets one of
each kind is called
MITOSIS
A Chromosome is
TWO identical
strands of DNA
A Chromatid is ONE
of those two strands
The chromatids are
separated during
Mitosis
There are FIVE PHASES of Mitosis
Interphase
Metaphase
Telophase
They are:
Prophase
Anaphase
Followed by the actual
CYTOKINESIS!
cell division:
cell
movement
division
When a cell is about to divide,
the nucleus prepares to divide first.
The Chromosomes appear!
(The lines are being reeled in.)
This phase is called
PROPHASE
The chromosomes line up
This is called
METAPHASE
Then the chromatids separate
This is called
ANAPHASE
Finally the nucleus
completes it’s division
The chromosomes begin to unwind
and new nuclear membranes appear
And forms a
cleavage furrow
This is called
TELOPHASE
After Nuclear Division (Mitosis)
the cell divides in half.
This is called
Cytokinesis
Each of the two new cells then
enters a growth phase
called
INTERPHASE
The five Phases of MITOSIS
Football game analogy
They are: Interphase
Centrioles
Intermission: The game
hasn’t begun yet
The five Phases of MITOSIS
Football game analogy
Prophase Metaphase Anaphase Telophase
Players
WickedMet
Witch AnnaNew
casts
locker
a spell.
rooms
Ropes
appear
The Pros show up
drag
atappear)
Lineup
the players into their
around
own
them
endand
zones
the
(the chromosomes
Noooooooooooooo!
terrified players
telephone home!
CYTOKINESIS
Football game analogy
The ground begins to shake!
A crack in the earth appears
along the fifty yard line!
CYTOKINESIS
Football game analogy
Where there was one stadium
there are now two!
Interphase
Mitosis in Plant Cells
Metaphase
Telophase
Prophase
Anaphase
CYTOKINESIS!
cell
movement
division
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Mitosis vs. Meiosis
Mitosis
Meiosis
Produces body cells
Produces sperm cells
or egg cells
Mother cell divides into
two daughter cells
Mother cell divides into
four daughter cells
Chromosomes initially
line up in one line
Chromosomes initially
line up as pairs
The daughter cells
are diploid
The daughter cells
are haploid
(2 of each kind)
46 Chromosomes / cell
(1 of each kind)
23 chromosomes / cell
Tetrads
Chromosome #1
from your dad
Tetrads
Chromosome #1
from your mom
Division I
Division II
Prophase
Prophase I
Metaphase
Metaphase I
Anaphase
Anaphase I
Telophase
Prophase II
Metaphase II
Anaphase II
Lets compare Sperm making (Spermatogenesis)
with Egg making (Oogenesis)
Pronounced “OH OH Genesis”
One cell gets all
the cytoplasm
One cell gets all
the cytoplasm
Cancer
These mutated cells no longer respond to
signals that regulate growth and division
The cells grow and divide rapidly forming
a ball of cells called a tumor
Cancer Cells may be
carried in the blood
stream to other
places
This is called
Metastisis
Liver Cancer