A CELL’S ROLE IN
CREATING AN
ORGANISM
Uni-cellular organism
•Organism
is composed of a singe cell
•Single cell performs all life functions
•Examples: yeast, bacteria
Multicellular Organisms
•Organism
composed of more than
one cell
•Examples: plants, animals
•Cells
develop special jobs and group
together in an organized way . . .
Mutlicellular Organism
•Levels of organization
cells -->
tissues -->
organs -->
organ systems -->
organisms
•Cells
•Are
the basic unit
of structure and
function in living
things
•Examples- blood
cells, nerve cells,
bone cells, etc
•Tissues
•Made
up of groups
of similar cells that
perform a
particular function
•Examples—
connective,
epithelial, muscle,
and nerve
•Organs
•Made
up of tissues
that work
together to
perform a specific
activity
•Examples - heart,
brain, skin, etc.
•Organ
systems
•Groups
of two or more
organs that work
together to perform a
specific function for
the organism.
--Examples - digestive
system, nervous system,
skeletal system, etc.
•Organism
•Entire living
thing that can
carry out all basic life
processes
Essential Question
•How
do organisms get to be
MULTI-cellular?
Cell growth and Division
•
Why can’t cells get infinitely
large?
1. Because
the info stored in
DNA can only meet the needs
of a limited sized cell . . . Too
big of a cell leads to an
“information crisis”
Why can’t cells get infinitely
large?
2.Because a cell that is too big
can not efficiently have
nutrients delivered and
wastes removed
Diffusion and Cell Size Lab
Limits to cell size
•DNA overload
•Problems exchanging materials
•Ratio of surface area to volume
Surface Area
Surface Area
Surface Area
How do cells divide?
Cell division is a pattern of growth and
division for the cell.
The cell will grow so that when it divides
it will be the proper size and the new cell
will have all of the “parts” that it needs.
Cells will continue to do this until they
die.......
The cell cycle focuses on what happens in
the nucleus……. So lets first get to know
the terms associated with our DNA.
•Every cell has 6 feet of
DNA inside its nucleus!
How does the cell fit 6 ft of DNA in
a nucleus?
•The DNA is tightly packaged
inside the nucleus.
•We will see how this works on
the next slide.
Chromatin:
•DNA and proteins spread out loosely in
the nucleus
•Like a bowl of spaghetti
Chromosome:
Long, rod-shaped structures composed of
DNA and proteins
Duplicated
Chromosome:
Even when it is duplicated it is still
considered a chromosome…..just
duplicated
*Each arm is now called a sister chromatid
held together at the centromere
*ONLY IN THIS STAGE WHEN THE CELL IS
DIVIDING!
Chromosome
Structure:
Super Coiling of
DNA
(YouTube Clip—click image)
Chromosomes are
formed from a
single DNA strand
that contains
MANY genes

NOTE: Gene = a region of DNA that
controls a hereditary characteristic (trait)
1 chromosome = 1-strand of DNA
How many strands of DNA do we
have in a normal body cell?
46
1. Every species has a set number of
chromosomes in each cell
2. Humans have 46 chromosomes (23
pairs) in EVERY cell with the
EXCEPTION of sex cells
Check out other
organisms!
1.
2.
SEX CHROMOSOMES
–
chromosomes that determine the sex of
an organism
–
Humans…Normal Female = XX
Normal Male = XY
–
Chromosome pair #23
AUTOSOMES
• All of the other chromosomes in an
organism.
• Chromosome pairs #ed 1-22
• Organisms receive one copy of
each autosome from each parent
•So we have 23 pairs!
•One from mom and one from Dad
• The two copies of each autosome
are called HOMOLOGOUS CHROMOSOMES
•Their “bands” line up!
HOMOLOGOUS CHROMOSOMES
= chromosomes
of the same
size, shape, and
banding
pattern. One
chromosome of
the pair came
from each
parent.
1. Haploid (1n) = cells that contain
ONE SET of chromosomes
(germ cells/sex cells/gametes)
2. Diploid (2n) = cells that contain
TWO SETS of chromosomes
(somatic cells / body cells)
i.e. When a
sperm cell
(1n) and an
egg cell (1n)
combine, the
new cell will
be diploid
(2n)
1.
2.
Karyotype:
A picture of the chromosomes in a
dividing cell
Used to examine an individual’s
chromosomes
K
a
r
y
o
t
y
p
e
Normal
Male
K
a
r
y
o
t
y
p
e
Karyotype
BEFORE
Mitosis
http://wise.berkeley.edu/student/topFrame.php?projectID=23132
Karyotype
AFTER
Mitosis
http://wise.berkeley.edu/student/topFrame.php?projectID=23132
Haploid cell
Diploid cell
http://scigjt13.wordpress.com/2011/03/02/karyotype-of-alzheimers-disease/
Remember:
How many chromosomes do
humans have?
The Cell Cycle: Interphase and Mitosis
Mitosis is a process that helps
organisms grow, develop, and heal.
Mitosis refers to the division of “body
cells.” Think My Toe
(AKA--Mitotic Phase)
INTERPHASE:
Centrioles
• Period of cell
growth and
development
that precedes
mitosis and
follows
CYTOKINESIS
(cell splitting)
• Longest phase
of the cell
cycle
1. G1 = Growth 1—most cell growth (cell contents are
duplicated)
2. S = Synthesis—DNA is duplicated
3. G2 = Growth 2—cell grow a little to prepare for division
and “double checks” for errors
1. PROPHASE:
•
•
Chromatin condense and
thicken – now called
chromosome. (DUPLICATED)
The nuclear envelope breaks
down
• Centrioles
move to opposite
"poles“ (or ends)
of the cell
2. METAPHASE:
1.
2.
The spindle fibers
(centriole) fully
develops
The duplicated
chromosomes align
at the metaphase
plate (middle)
3. ANAPHASE:
1.
2.
3.
Sister chromatids of the
duplicated chromosomes
separate and begin
moving to opposite ends
(poles) of the cell.
Spindle fibers lengthen
and elongate the cell.
Each pole contains a
complete set of
chromosomes.
4. TELOPHASE:
1. Nucleus begins
to form at
opposite poles.
2. The nuclear
envelopes and
nucleoli also
reappear.
CYTOKINESIS:
= the division of the original
cell's cytoplasm. (There are
now two separate cells)
Cytokinesis: Animal Cell vs. Plant cell
Animal Cell
• Cleavage furrow
forms and pinches
cell in half.
http://wps.aw.com/bc_campbell_concepts_5/30/7910/2025031.cw/index.html
Cytokinesis: Animal Cell vs. Plant cell
Plant Cell
• Cell plate forms to
divide the cell.
http://wps.aw.com/bc_campbell_concepts_5/30/7910/2025031.cw/index.html
CELL CYCLE
MITOSIS
1.Prophase
1. Interphase
2.Metaphase
2. Cell
3.Anaphase
Division
(Mitosis +
Cytokinesis)
4.Telophase
Cell Cycle Regulation
 Cell growth and division are carefully controlled.
 Not all cells will go through the cell cycle at the
same rate.
• Examples of cells
rapidly dividing:
• Examples of cells
NOT dividing often:
http://stearn.ca/blog/wp-content/uploads
/2009/05/red-blood-cells.bmp
http://www.caring4cancer.com/uploadedImages/Website-C4C-20/Skin
_Cancer_(Non-Meloma)/The_Basics/Epidermis-dermis.jpg
http://apps.uwhealth.org/adam/graphics/images/en/19917.jpg
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=
cooper&part=A1967&rendertype=figure&id=A1982
http://www.rush.edu/rumc/images/ei_0062.gif
http://activebodyreadymind.com/images/Nerve.jpg
Cell Cycle Regulation continued . . .
 Cells that do not need to grow and divide can
enter G0 (resting) until they are needed.
Regulation
 Cells have both internal and external regulators.
Are all of the chromosomes attached
Is the cell
to spindle fibers and properly
big enough?
aligned on the metaphase plate?
• Internal
regulators—are
called cyclin and
they make sure
the cell is ready at
certain
checkpoints . . .
If not, the cycle
stops (see diagram) Has all of the DNA
duplicated completely
or properly?
Is the cell big enough?
Regulation continued . . .
• External regulators—
are called growth factors.
• If cells are touching
other cells = no growth
• If space with no
neighboring cells =
grow/divide
http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch8/ir/imagelib_tab_1/33.htm
http://www.yourcancertoday.com/ContentResources/Image/growth.jpg
Cancer
 Cancer = uncontrolled cell growth
. . . cancer cells do NOT respond to regulator signals
. . . results in masses of cells called tumors
. . . cancer = a disease of the cell cycle
http://www.youtube.com/watch?v=LEpTTolebqo&feature=related
Cancer:
•Results in masses of cells
called tumors –malignant
vs. benign
•Metastasize = travel
MEIOSIS:
GOING FROM DIPLOID
TO HAPLOID
Making Gametes: Egg and Sperm
CELL DIVISION WITH
MEIOSIS
Where do your
genes come
from?
The cell cycle remains the same
except…
G1
Division:
meiosis &
cytokinesis
G2
S
Video: Amoeba Sisters
Meiosis makes unique haploid cells.
As you study meiosis focus on two things:
•How are we ‘mixing things up’ so that our
offspring are unique?
•How are we moving and separating the
chromosomes so that we end up with ½ the
material?
Process of nuclear division that reduces the
number of chromosomes in new cells to
HALF the number in the original cell.
Diploid  Haploid
http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/
Sex Cells (Gametes) are Haploid: ½ the genetic information!
Meiosis results in . . .
Sex Cells
a. Female gamete = egg cell
b. Male gamete = sperm cell
Images from: http://www.giantmicrobes.com/us/products/eggcell.htmland http://photovalet.com/68969
Cells undergo all the phases of interphase
 Then they enter MEIOSIS which involves
TWO distinct cell divisions
Division 1
Image from: http://www.citruscollege.edu/lc/archive/biology/Pages/Chapter09-Rabitoy.aspx
Division 2
Checkpoint:
1.
What happens during interphase?
2.
Where in an organism’s body will cells carry out
meiosis?
Before Meiosis I happens, the cell will go
through interphase:
G1, S, G2 (just like Mitosis)
1. Meiosis I
a. Prophase I
(crossing over)
b. Metaphase I
c. Anaphase I
(homologous chromosomes separate)
d. Telophase I and cytokinesis
Prophase I
Prophase I is the longest and most
complex phase.
All of the events that
occurred during
prophase of mitosis
occur +
Homologous
chromosomes come
together to form a
SYNAPSE (TETRAD).
CROSSING-OVER occurs.
Crossing Over:
Portions of chromatids break
off and attach to adjacent
chromatids on the
homologous chromosome
This allows for more genetic
variability! We don’t want
everyone to look the same.
 Occurs during Prophase I
Metaphase I
•Homologous chromosomes
line up randomly at
the center of the cell. We call this
independent assortment.
•Instead of all the chromosomes lining up in
Metaphase in a single-file line, they will
pair up with their homologous partner
Mitosis
Meiosis
Metaphase I
SOCKS!!!!!
Lets practice with homologous
chromosomes
Anaphase I
• During
anaphase the homologous chromosomes in
the center of the cell divide.
Telophase I / Cytokinesis
•Telophase I two nuclei form (23 duplicated
chromosomes in each)
•Cytokinesis occurs resulting in 2 haploid
daughter cells.
Interphase
Prophase
I
Metaphase
I
Anaphase
I
Cytokinesis
Telophase
I
Images from: http://www.phschool.com/science/biology_place/biocoach/meiosis/teloi.html
Meiosis II
• Meiosis
II comes directly after cytokinesis. No growth
(interphase) takes place.
• Meiosis II is broken into 4 events:
• prophase
II
• metaphase II
• anaphase II (sister chromatids separate)
• telophase II and cytokinesis ( 4 haploid cells)
• The
steps of Meiosis II are identical to mitosis.
Prophase II
• Prophase
II is the same
as prophase in mitosis.
• Chromatin condenses
into chromosomes
• Nuclear envelope breaks
down
Metaphase II
• Metaphase
II is the same as
metaphase in mitosis.
• Duplicated chromosomes line
up in the middle of the cell
• Spindle fibers from the
centrioles
attach to each sister chromatid
Anaphase II
• Anaphase
II is the same as
anaphase in mitosis.
• Sister chromatids separate.
Telophase II
• Telophase
II is the same as
telophase in mitosis.
• At the end
of the second Cytokinesis
in Meiosis there are 4 haploid cells
• Males:
4 sperm
• Females: 1 egg + 3 polar bodies
Coming from Meiosis I
Prophase II
Metaphase II
Anaphase II
Images from: http://www.phschool.com/science/biology_place/biocoach/meiosis/teloi.html
Telophase II
Cytokinesis
Checkpoint:
1.
When did crossing over occur?
2.
When do homologous chromosomes
separate?
3.
Why are sex cells haploid?
4.
When do the sister chromatids separate?
Meiosis I =
separates homologous
chromosomes
Meiosis II =
separates sister
chromatids
Image from: http://wise.berkeley.edu/student/topFrame.php?projectID=23132
•
•
•
•
Down Syndrome
(Trisomy 21)
Sister
chromatids fail
to separate
properly during
meiosis II
Non-disjunction:
Klinefelters (XXY) and Turner Syndrome (X)
At the end of meiosis II four UNIQUE
daughter cells are produced (4 haploid
cells)