Cell Reproduction
Cells Division Introductory Video
• During cell division the
cell’s DNA is coiled
compactly into a
CHROMOSOME
• Each chromosome is a
single DNA molecule
• The DNA wraps tightly
around a protein called
HISTONE (helps maintain
the chromosome’s shape)
The
Chromosome
Anatomy of a Chromosome
• Each half of a chromosome is
called a CHROMATID
• Chromatids form as the DNA
copies itself before cell division
• The 2 Chromatids are attached at
a point called a CENTROMERE
• CHROMATIN=less tightly areas of
DNA between cell divisions
Chromosome Numbers
• Every species has a certain number of
chromosomes in each cell.
• Animal chromosomes are either:
• Sex Chromosomes—will determine the
gender of an organism (X and Y)
• Autosomes—all of the other
chromosomes
• Cells with 2 sets of Chromosomes are
DIPLOID
• Cells with one set of chromosomes are
HAPLOID (sex cells…half the number of
chromosomes)
Chromosomes Clip
• How many chromosomes does a potato have?
• How many chromosomes do Ferns have?
• After the video…in your own words why do different
organisms have different numbers of chromosomes??
Cell Division (aka Cell
Reproduction) in Prokaryotes
•Most prokaryotes
reproduce by BINARY
FISSION
•2 identical cells are
produced from one
cell
Cell Division Eukaryotes
• Two types of Cell Division
(Reproduction) in Eukaryotes!
• Mitosis=new cells with
identical genetic material
• Meiosis=reduces the number
of chromosomes by half for
the purpose of eventual
reproduction
• Memory trick:
• My toe and Me
Mitosis
Meiosis
The Cell Cycle
• The CELL CYCLE
is the repeating
events of the life
of a cell.
• Interphase is the
period between
cell divisions
• Draw the
diagram
How do little elephants grow up to be BIG elephants?
Three reasons why cells reproduce by
asexual reproduction or MITOSIS:
1. Growth
2. Repair
3. Replacement
Mitosis Cycle
• Interphase (technically
NOT a phase of Mitosis)
• Prophase (first phase)
• Metaphase
• Anaphase
• Telophase & Cytokinesis
Interphase
occurs before mitosis begins
• Chromosomes are copied (# doubles)
• Chromosomes appear as threadlike coils (chromatin) at the
start, but each chromosome and its copy(sister
chromosome) change to sister chromatids at end of this
phase
Nucleus
CELL
MEMBRANE
Cytoplasm
Interphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase
1st step in Mitosis
• Mitosis begins (cell begins to divide)
• Centrioles appear and begin to move to opposite end of the
cell.
• Spindle fibers form between the centrioles.
• DNA is coiled into chromosomes (X-shapes)
Centrioles
Sister chromatids
Spindle fibers
Prophase
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
2nd step in Mitosis
•Chromatids (or pairs of chromosomes)
attach to the spindle fibers and meet in
the middle
•Chromosomes/chromatids are easily
identified in this stage
Centrioles
Spindle fibers
Metaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase
3rd step in Mitosis
• Chromatids separate and begin to move
to opposite ends of the cell.
Centrioles
Spindle fibers
Anaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase
4th step in Mitosis
• Two new nuclei form.
• Chromosomes uncoil and become chromatin, the new
nucleus forms around it
• Mitosis ends.
Nuclei
Chromatin
Nuclei
Telophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis
occurs after mitosis
• Cell membrane moves inward to create
two daughter cells – each with its own
nucleus with identical chromosomes.
• The cell splits into 2
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Plant Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
REMEMBER!
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
IPMATC
I P___ M___ A___ T___ C______
It’s your turn! Identify the stages of mitosis in
Onion cells…
Control of Cell Division!
• What triggers a cell to leave interphase and
begin dividing? What tells the cell to stop?
• Proteins regulate this process through a series of
‘check points’
• Certain signals at checkpoints tell the cell to
initiate the next step in the cell cycle or to halt
the cycle
3 Main Checkpoints
G1 Checkpointcell growthproteins control
whether the
cell will divide
or not
If cell is healthy
and the right
size, DNA
synthesis will
begin (S phase)
G2 Checkpoint-DNA
Synthesis– enzymes check
results of DNA
replication…if ok Mitosis
will begin
Mitosis Checkpoint: If
a cell passes this
checkpoint, proteins
signal the cell to exit
mitosis and it enters
G1 again
When Control is LOST: Cancer
• The proteins that regulate cell growth and division are
coded for by genes, proto-oncogenes.
• If a mutation occurs in one of those genes, the
proteins may not function properly and become
oncogenes.
• If the proteins don’t function properly Cancer can
result: an uncontrolled growth in cells
When Control is LOST: Cancer
• A TUMOR is an uncontrolled growth of unnecessary
cells.
• In a BENIGN tumor the cells stay in the mass and the
are generally harmless
• In a MALIGNANT tumor, the uncontrolled dividing
cells may invade and destroy healthy tissues= CANCER
Homework!
• Use the internet to find a list of cancers
• Choose 1 (must be cleared by teacher)
• You will create a Powerpoint that could help someone who has just been diagnosed with a particular
kind of cancer to understand his or her disease and its treatment options.
• Required:
• Cancer type
• 5 or more pictures/clipart/video clips
• Your name and period
• Symptoms associated with this type of cancer
• Risk factors – what makes people more likely to get it? Is it genetic or caused by a carcinogen, or both?
• How common is it?
• Is any particular group more likely to get it than another?
• Treatment Options
• Interesting facts
• 5 slides or more
Vocabulary
1.
2.
3.
4.
5.
6.
7.
8.
Chromosome
Histone
Chromatid
Centromere
Chromatin
Sex chromosome
Autosome
Homologous
chromosome
9. Karyotype
10. Diploid
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Haploid
Binary fission
Mitosis
Asexual reproduction
Meiosis
Gamete
Interphase
Cytokinesis
Prophase
Spindle fiber
Metaphase
22.
23.
24.
25.
26.
27.
28.
29.
Anaphase
Telophase
Cell plate
Synapsis
Tetrad
Crossing over
genetic recombination
Independent
assortment
30. Sexual reproduction
Photo Sort
●
In your group arrange the members of the family in
a way that shows their relationships.
●
This should look like a family tree.
●
Label the relationships.
Sacramento Area Science Project©, Use with attribution
http://sasp.ucdavis.edu
Family Tree Example
Sacramento Area Science Project©, Use with attribution http://sasp.ucdavis.edu
What criteria did you use?
-Doodle A-
Sacramento Area Science Project©, Use with attribution
http://sasp.ucdavis.edu
P. 5
Craig Robinson(Michelle’s Brother), Leila and Avery Robinson (Craig’s kids), Marian Robinson
(Michelle’s Mother), Michelle, Sasha, President Obama, Malia, Akinyi Manners (Obama’s niece, Auma’s
daughter), Auma Obama (half-sister dad’s side), Mays Soetoro Ng (half sister mom’s side), Konrad Ng
(Maya’s husband), Savita and Suhaila Ng (Obama’s nieces)
When you have the same parents,
how is it that some siblings look similar
and some different?
Sacramento Area Science Project©, Use with attribution
http://sasp.ucdavis.edu
Meiosis
Meiosis – key differences from mitosis
•Meiosis reduces the number of chromosomes by
half, producing GAMETES (sperm and egg cells in
humans).
•Daughter cells differ from parent, and each
other.
•Meiosis involves two divisions, Mitosis only one.
Meiosis KM
43
Meiosis I (four phases)
• Cell division that reduces the chromosome number
by one-half.
• four phases:
a. prophase I
b. metaphase I
c. anaphase I
d. telophase I
Interphase I
• Similar to mitosis interphase.
• Chromosomes replicate (S phase).
• Each duplicated chromosome consist of two identical
sister chromatids attached at their centromeres.
• Centriole pairs also replicate.
Interphase I
• Nucleus and nucleolus visible.
chromatin
nuclear
membrane
cell membrane
nucleolus
Prophase I
• Longest and most complex phase (90%).
• Chromosomes condense.
•Synapsis occurs: homologous chromosomes
come together to form a tetrad.
Unique to
MEIOSIS
•Tetrad is two chromosomes or four
chromatids (sister and nonsister chromatids).
Homologous Chromosomes
• Pair of chromosomes (maternal and paternal) that are similar in shape and
size.
• Homologous pairs (tetrads) carry genes controlling the same inherited traits.
• Each locus (position of a gene) is in the same position on homologues.
• Humans have 23 pairs of homologous chromosomes.
a.
b.
22 pairs of autosomes
01 pair of sex chromosomes
Homologous Chromosomes
eye color
locus
eye color
locus
hair color
locus
hair color
locus
Paternal
Maternal
Prophase I - Synapsis
Homologous chromosomes
sister chromatids
Tetrad
sister chromatids
Prophase I
spindle fiber
aster
fibers
centrioles
Crossing Over
• Crossing over (variation) may occur between
nonsister chromatids
• Crossing over: segments of nonsister chromatids
break and reattach to the other chromatid.
• Crossing Over creates genetic recombination (variety)
Crossing Over - variation
nonsister chromatids
chiasmata: site
of crossing over
Tetrad
variation
Crossing-Over
Crossing-over multiplies the already huge number of
different gamete types produced by independent
Metaphase I
•Shortest phase
•Tetrads align on the metaphase
plate.
Metaphase I
OR
metaphase plate
metaphase plate
Anaphase I
• Homologous chromosomes separate and move
towards the poles.
• Sister chromatids remain attached at their
centromeres.
• INDEPENDENT ASSORTMENT OCCURS:
1. The random separation of the homologous
chromosomes---this results in GENETIC VARIATION
Anaphase I
Telophase I
• Each pole now has haploid set of
chromosomes.
• Cytokinesis occurs and two haploid
daughter cells are formed.
Telophase I
Meiosis II
•No interphase II
(or very short - no more DNA replication)
•Remember: Meiosis II is similar to mitosis
Prophase II
• same as prophase in mitosis
Metaphase II
• same as metaphase in mitosis
metaphase plate
metaphase plate
Anaphase II
• same as anaphase in mitosis
• sister chromatids separate
Telophase II
• Same as telophase in mitosis.
• Nuclei form.
• Cytokinesis occurs.
Remember:
• four haploid daughter cells
• gametes = sperm or egg
produced.
Telophase II
Meiosis – mouse
Parent cell
1st division
2nd division
4 gametes
Sex Chromosomes
The Sex Chromosomes code for the sex of the offspring.
** If the offspring has two “X” chromosomes it will be a female.
** If the offspring has one “X” chromosome and one “Y” chromosome it will be
a male.
In Humans the
“Sex
Chromosomes”
are the 23rd set
XX chromosome - female
XY chromosome - male
Boy or Girl? The Y Chromosome “Decides”
Y chromosome
X chromosome
Cells Dividing Clip
Crash Course Meiosis
Compare/Contrast Mitosis and Meiosis