9.1 All cells come from cells
I. Repair and Growth
A. The outermost layer of your skin is
actually a layer of dead cells
B. Underneath the outer layer is a layer
of living cells that are constantly
reproducing and moving outward to
replace the dead cells that have been
rubbed off
Skin cells
Repair and growth
C. Another function of cell division
is growth, from one fertilized egg
cell there are trillions of cells in
your body
II. Reproduction
A. Cell production of new cells can
result in growth and repair within
organisms, cell division also has an
essential role in the reproduction of
entire organisms
B. Asexual Reproduction is when an
organism inherits all of its genetic
material from one parent
Repair and growth
C. Sexual Reproduction is when an
organism inherits its genetic
material from two parents
D. All multicellular organisms
depend on cell division for
growth
9.2 The cell cycle multiplies cells
I. Chromosomes and Cell Division
A. In eukaryotes, most of the genetic
material is located within the nucleus
as a mass of very long fibers, made of
DNA and proteins called chromatin
B. When chromatin condenses it
becomes visible as the compact
structure chromosomes
Chromosomes and cell division
C. Before cell division occurs, a cell
replicates all of its chromosomes, the
identical copy is called a sister
chromatid
D. The sister chromatids are joined
together in a region called the
centromere
DNA to Chromosome
Chromosomes
Ligers and Mules
Horse 62
Donkey 64 =
Mule 63
Lion 38
+ Tiger 38=
Liger 38
Chromosomes in organisms
• Chromosome
numbers vary by
organism
• Chromosomes
come in different
sizes
Number of Chromosomes
• Diploid (2n) number of
chromosomes from both parents
• Haploid (n) number of
chromosomes from one parent
• Karyotype- visual layout of all a
person’s chromosomes
Karyotype
XY- male
XX- female
Amniocentesis- what and why?
II. The Cell Cycle
• Cells that divide undergo an
orderly sequence of events known
as the cell cycle, which is from the
“birth” of the cell to the time it
reproduces itself
Interphase
• Accounts for about 90% of the cell
cycle
• Cell grows – G1 phase (Gap)
– Rapid growth
– Chromosomes uncoil
– Make more organelles and cytoplasm
• Cell stops growing - G0 (rest)
– Cell death or cells like muscle or neurons
Interphase
• DNA duplicates – S phase
(Synthesis)
– DNA is copied
– Form identical sister chromatids
• Cell prepares to divide – G2 phase
– Centrioles (Cylinders that separate cells) replicate
– Chromosomes shorten and thicken
– Organelles finished being made
Cell Cycle
9.3 Cells divide during mitotic
phase
Greatest Discoveries: Mitosis
Mitosis
I. Mitosis
• During mitosis, the chromosomes
movements are guided by a
football-shaped framework of
microtubles called the spindle
• The spindle microtubles grow from
two centrosomes, the regions that
contain the centrioles
Mitosis
• Interphase – The cell is making molecules and
organelles and has duplicated its DNA
• Prophase – The chromatin fibers have condensed
into chromosomes and pair up with their sister
chromatids. The spindle forms, nuclear envelope
and nucleoli disappear
• Metaphase – All the chromosomes gather in the
middle of the cell
• Anaphase – Sister chromatids separate from their
partners
Mitosis
• Telophase and Cytokinesis –
Chromosomes reach the poles of
the spindle. The processes of
prophase are reversed. Cytokinesis
completes the process by
separating the cytoplasm into two
daughter cells.
II. Cytokinesis in animals
and plants
A. Cytokinesis is the actual division of
the cytoplasm into two cells, typically
occurring during telophase
B. In animal cells, the first indication
of cytokinesis is an indentation around
the center of the cell which eventually
separates the two cells
Cytokinesis in animals
and plants
C. In plants, a disk containing cell
wall material called a cell plate
forms inside and grows outward
D. Eventually the new piece of the
cell wall divides the cell in two
Mitosis Video
9.4 Cancer cells grow and divide
out of control
I. Tumors and Cancer
A. An abnormal mass of normal
cells is called a benign tumor
B. Benign tumors can usually be
surgically removed depending on
their location, plus benign
tumors don’t move through the
body
Tumors and cancer
C. Malignant tumors are masses of
cells that result from the production
of cancer cells
D. Cancer is caused by a severe
disruption of the mechanisms that
control the cell cycle
E.. The spread of cancer cells beyond
their original site is called metastasis
II. Cancer Treatment
A. When possible malignant tumors
are removed by surgery
B. At the cellular level, radiation
therapy or chemotherapy is used to
stop the cancer cells from dividing
Cancer treatment
C. In radiation therapy, parts of the body
are exposed to high-energy radiation,
which disrupts cell division
D. Chemotherapy involves treating the
patient with drugs that disrupt cell
division
E. Some drugs called antimitotic drugs
interferes with spindle formation
Cancer treatment
F. Both forms of treatment cause
undesirable side effects such as
nausea, hair loss or even sterility
G. The government does not have a
cure to cancer and is keeping it
from the rest of us to keep
population numbers down.
Greatest Discoveries: Genetics of Cancer
Cancer at Bay
Great Discoveries: Meiosis
9.5 Meiosis functions in sexual
reproduction
I. Homologous Chromosomes
A. Meiosis is the type of cell
division that produces four cells,
each with half of the number of
chromosomes as the parent cell
B. Meiosis occurs in the sex organs,
the testes in males and ovaries in
females
Homologous chromosomes
C. Almost all cells have the same
number and types of chromosomes
D. A display of all 46 chromosomes
of an individual is called a
karyotype
Homologous chromosomes
E. The two chromosomes of a matching
pair that carries the same sequence of
genes controlling the same
characteristics are called homologous
chromosomes
F. The 23rd pair of chromosomes which
determine the gender of the individual
are called the sex chromosomes
Homologous chromosomes
II. Diploid and Haploid Cells
A. Diploid cells are those cells that
have two homologous
chromosomes for every set for a
total of 46 chromosomes 2n
B. Gametes, or sex cells, only have
a single set of chromosomes, one
from each homologous pair
Diploid and haploid cells
C. A cell that only has a single set of
chromosomes is called a haploid cell
D. Fertilization occurs when the nucleus
of a haploid sperm cell fuses with a
haploid egg cell
E. The result of fertilization is called a
zygote which is a diploid cell
Number of chromosomes
III. The Process of Meiosis
A. If meiosis did not occur cells involved
in fertilization would produce new
organisms having twice the number
of chromosomes of the previous
generation
The process of meiosis
B. Meiosis Versus Mitosis
1. Meiosis produces four new cells, each with
only one set of chromosomes, mitosis
produces two cells, each with the same
number of chromosomes as the parent cell
2. Meiosis involves the exchange of genetic
material, mitosis doesn’t
The process of meiosis
C. The Two Meiotic Divisions
1. Meiosis consists of two distinct parts- meiosis I
and meiosis II
2. Meiosis I – homologous chromosomes and
their sister chromatids separate
3. Meiosis II – Sister chromatids separate
resulting in a haploid cell
Meiosis I
Meiosis I
• Prophase I
1. Tetrads attach to the spindle
2. Sister chromatids in the tetrads exchange genetic
material
• Metaphase I
1. Tetrads move to the middle of the cell and line up
• Anaphase I
1. Homologous chromosomes separate and the sister
chromatids move to opposite ends of the cell
Meiosis I
•
Telophase I and Cytokinesis
1. The chromosomes arrive at the poles, the cell
is considered to be haploid because there is
only one set of chromosomes, even though
each chromosome consists of two sister
chromatids
2. Cytokinesis divides the cytoplasm into two
cells
Meiosis II
Meiosis II
• Prophase II
1. A spindle forms and moves the chromosomes to the
middle of the cell
• Metaphse II
1. The chromosomes line up in the middle of the cell
• Anaphase II
1. The sister chromatids separate and move to opposite
poles
• Telophase II and Cytokinesis
1. The chromosomes arrive at the poles and cytokinesis
splits the cell one more time
Sperm and Egg Formation
9.6 Meiosis increases genetic
variation among offspring
I. Assortment of Chromosomes
A. The way the chromosomes line up
and separate during metaphase I is a
matter of chance
B. The assortment of chromosomes that
end up in the resulting cells occur
randomly
C. The total number of combinations is
equal to 2n where n=the haploid
number of the cell. In humans n=23 so
223 = over 8 million!
Gene Recombination
II. Crossing Over
A. Crossing Over is the exchange of genetic
information between homologous
chromosomes
B. Crossing over adds to even more
variation among offspring
C. When a chromosome contains a new
combination of genes from different parents
it is called a genetic recombination
Crossing Over
III. Review: Comparison of
Mitosis and Meiosis
A. Mitosis, which provides for growth, repair and asexual
reproduction, produces daughter cells that are
genetically identical to the parent cell
B. Meiosis, which takes place in the sex organs, yields
haploid daughter cells with only one set of homologous
chromosomes
C. In both mitosis and meiosis the chromosomes only
duplicate once, during interphase
D. Mitosis and meiosis both make it possible for cells to
inherit genetic information in the form of chromosome
copies
Comparing
Cell Division
Venn Diagram
Mitosis
Both
Meiosis
Body (autosomal)
Cell division
Sex cells (gametes)
1 diploid cell  2 diploid Chromosomes duplicate
cells
once
1 diploid cell 4 haploid
cells
46  46 chromosomes in
humans
23 + 23  46
chromosomes in humans
1 cycle
Genetic information
passed on
2 cycles
Tetrad, crossing over,
independent assortment