CELLULAR REPRODUCTION
5.1 The Cell Cycle & Mitosis
5.2 Cell Cycle Regulation & Cancer
5.3 Asexual Reproduction
5.4 Meiosis in Sex Cells
5.5 Sexual Reproduction, Fertilization, & Development
5.6 Sexual Reproduction vs. Asexual Reproduction
• All living things, that are made of cells, must be able
to grow and reproduce.
• Old cells will die, and must be replaced with new ones
(skin).
• Cells have an optimal (best) size. If they are too big or
too small, they cannot function properly.
DNA in the Cell:
• Chromosomes
• X shaped
• In dividing cells
• Made of sister chromatids
• Held together by a centromere
• Chromatin
• Squiggly shaped
• In NON dividing cells
Chromosomes & Chromatin are the SAME
thing, just shaped different.
Chromosome Labeled
Different Types of Cells:
• Somatic cells- BODY cells (make up cell in your body, like
heart, liver, skin, EXCEPT your sex cells; egg/sperm)
• Whole
• 46 (human) chromosomes
• Diploid
• 2n
• Identical to parent cells (like repairing a paper cut)
• Gamete Cells- SEX cells; make up the egg/sperm cells.
• Half
• 23 (human) chromosomes
• Haploid
•n
• NOT identical to parent cells
The Cell Cycle
• Somatic cells (BODY)
reproduce by the cell
cycle/mitosis.
• The Cell Cycle is divided into 3
parts/phases:
1. Interphase
2. Mitosis
3. cytokinesis
1. Interphase
• Stage in which the cell grows; DNA is copied
• Longest phase of the cell cycle (90% of the whole
cycle)
• Centrioles are present (these are organelles found in
animal cells that help the cell divide)
• Divided into 3 parts:
A. G1
B. S
C. G2
1. G1 (first gap)- the cell grows and proteins
needed for cell division are made
• G0- an extension of the G1 phase; the cell is
in a dormant/inactive state (asleepish). Cells
that live a long time (nerve cells/neurons)
remain in this state because they do not
undergo cell division
2. S (synthesis)- DNA replicates (makes
more) in the nucleus to make more
chromosomes.
3. G2 (second gap)- the cell grows and
synthesizes (makes) more organelles,
proteins, and spindles start to form
Interphase
• chromatin
• centrioles
2. Mitosis (M Phase)
• Stage where the nucleus and cytoplasm divides.
• Stage that is responsible for passing genetic
information to the cells
• 4 main stages:
A.
B.
C.
D.
Prophase
Metaphase
Anaphase
Telophase
A. Prophase
• Chromatin turns to chromosomes
• Nucleolus disappears
• Nuclear envelope/membrane
disappears
• Centrioles move to opposite sides of
the cell
• Microtubules form spindles (help split
chromosomes)
PROPHASE
• Chromosomes
• Spindle fibers
B. Metaphase
• Spindles attach to chromatids
• Chromosomes line up on equator (MIDDLE) of cell
METAPHASE
• Lined up in middle
(meta/middle)
C. Anaphase
• Chromosomes are pulled apart into chromatids
ANAPHASE
• Chromatids
pulled apart
(ana/apart)
D. Telophase
• Chromosomes have reached
opposite ends of the cell.
• Spindles disappear
• Nuclear envelope/membrane
reappears
• 2 nuclei have formed
• Cleavage furrow present
TELOPHASE
• Opposite sides
• Spindles disappear
• Cleavage furrow
CLEAVAGE
FURROW
(I)PMAT
•Interphase
•Prophase
•Metaphase
•Anaphase
•Telophase
3. Cytokinesis
• The division of they cytoplasm
• Plants and animals cytoplasm
divides differently
• Plants- a cell plate forms in
between the 2 cells (bc they
have a cell wall)
• Animals- the cell membrane
pinches in (cleavage furrow)
copyright cmassengale
23
copyright cmassengale
24
Name the Mitotic Stages:
Interphase
Name this?
Prophase
Telophase
Name this?
Metaphase
Anaphase
copyright cmassengale
25
Mitosis Animation
Name each stage as you see it occur?
copyright cmassengale
26
The Knit of Identity - Mitosis Precisely and Evenly Divides
Duplicated Chromosomes
interphase
prophase
metaphase
Mitosis Precisely and Evenly Divides Duplicated Chromosomes
Mitosis animation
Name the Stages of Mitosis:
Early Anaphase
Early prophase
Metaphase
Interphase
Late
Prophase
Late telophase,
Mid-Prophase
Advanced
cytokinesis
copyright cmassengale
Early
Telophase,
Begin
cytokinesis
Late
Anaphase
31
It takes about 24
hours for a cell to
undergo the cell
cycle (interphase,
mitosis, and
cytokinesis).
Interphase: 20 hrs
Mitosis: 1 hr
Cytokinesis: 3 hrs
Regulating the Cell Cycle
• For organisms to grow, cells must divide.
• Special proteins and enzymes located inside of the cell
help it divide/grow (the info in DNA gives these
proteins/enzymes the instructions)
• 2 factors help regulate cell growth:
A. External signals
B. Internal checkpoints
A. External Signals
• Growth factors
(proteins outside the
cell) signal the cell to
start dividing.
• Sometimes called “go”
signals
• Bind to receptors on
the cells
• Some are very specific
B. Internal Checkpoints
• Happens after external factors signal the cell to start
dividing
• Checkpoint= stop
• If something is wrong at a checkpoint, the cell cycle
will stop and will not start again until it is fixed.
• Special proteins and enzymes called cyclins and
kinases control this process.
• If there is a “problem” at a checkpoint, apoptosis will
occur (next slide)
Apoptosis
• Programmed cell death.
• Occurs when cells are damaged/worn
out, or if there is a problem at an
internal checkpoint
• Plays a BIG role in the fetal development
of tissues and organs
• A human embryo has webbed fingers and
toes; apoptosis is responsible for the
disintegration (breakdown) of the
webbing to make your fingers and toes
look normal.
Checkpoints:
• G1 Checkpoint- determines if the cell has reached the
right size and has enough energy and nutrients to
continue through the cell cycle (if not, it will not go to
the S phase)
• G2 Checkpoint- size is evaluated, again, and
chromosomes are looked at to see if they duplicated
correctly.
• M Checkpoint- takes place at the end of metaphase;
ensures that sister chromatids are attached to the
spindles
QUESTION:
RBCs carry oxygen to other cells in the body. When
oxygen levels in the body become low, specialized cells
in the kidneys release a protein called erythropoietin,
or EPO. EPO signals bone marrow cells to create more
RBCs. In what way does EPO signal bone marrow cells to
create more RBCs?
EPO acts as an external growth factor. It acts as a “go”
signal for the cell cycle to begin.
Disruption of the Cell Cycle
• Sometimes a “bad” cell will sneak by the
checkpoints and the cell cycle will
continue.
• If this happens, it may result in
uncontrolled cell growth/division
• This is called a disruption of the normal
cell cycle
• A mass of cells that grow out of control is
called a tumor.
• Tumors can be benign (NOT cancer;
sometimes called cysts) OR malignant
(cancer)
Cancer
• Results from cells growing/dividing abnormally and
then invading healthy tissues.
• Can be caused by environmental factors (carcinogens)
• Carcinogens- damage DNA in cells and transform the
cells into cancer cells
• Asbestos
• UV radiation
• X rays
• Some viruses
• Cigarette smoke
• Carcinogens can cause a
mutation in gene
• This is a permanent
change in the DNA
sequence
• If a gene becomes
mutated, it can become
and oncogene (a gene
that can cause cancer)
Metastasis
• The spread of cancer to other areas
of the body and occurs when cancer
cells grow and break off from their
“home” tissues and travel through
the blood stream or lymph vessels.
• They carry the cancer to new places
• We treat this with chemotherapy
drugs
• These drugs disrupt the cell cycle of the
cancer cells but also disrupt the cell
cycle of normal cells
REPRODUCTION
• The production of offspring (children) from one OR
two parents (sets of DNA).
• Reproduction is not necessary for the survival of a
single organism but for a species as a whole.
• Two types of reproduction:
• Asexual
• Sexual (will discuss in section 5.5)
Asexual Reproduction
• One organism as parent (one set of DNA)
• Genetically identical to parent
• Happen due to mitosis
• Produces a large number at once
• Happens quickly
4 Major Types of Asexual Reproduction:
1.
2.
3.
4.
Binary fission
Budding
Vegetative propagation
Regeneration and Fragmentation
1. Binary Fission
• Occurs in unicellular organisms
(bacteria; paramecium)
• Most simple type
• Cell grows; replicates the DNA;
splits in half
• All prokaryotes reproduce this way
• Identical to parent
• Mitosis
• Antibiotics kill bacteria by
interrupting the cell cycle
2. Budding
• A small area of the parent
starts to grow and then
detaches and becomes a
separate organism
• Identical to parent
• mitosis
• Examples: fungi and simple
animals (hydra, sea anemones,
yeast)
3. Vegetative Propagation
• Occurs in plants
• basically budding
• A parent plant forms a
“creeping” stem that roots
and forms a new plant
• Identical to parent
• mitosis
4. Regeneration & Fragmentation
• Occurs in simple animals (starfish,
sponges, planaria)
• can repair their bodies if a piece gets
broken off or damaged.
• Regeneration- growing a new body part
• Fragmentation- if enough DNA is in the
broken piece, it can grow a whole new
organism
• Identical
• Mitosis
Types of Cells:
• Organisms that reproduce sexually have 2 types of
cells:
a. Somatic cells
• Body cells
• Mitosis
• Identical
• Diploid (46)
• 2n
b. Gametes
• Sex cells (egg/sperm)
• Meiosis
• NOT identical
• Haploid (23)
•n
Haploid + Haploid = Diploid
Homologous Chromosomes/Pairs
• In somatic cells, 1 chromosome from each parent
“sits” by each other
• Example: eye color “sits” by eye color
Meiosis
• Occurs in reproductive cells (egg/sperm)
• NOT identical to parent
• Produce haploid cells
• Occurs when a chromosome from mom and a
chromosome from dad “mix up”
• This is called crossing over.
• Results in recombination or genetic variation
Crossing Over
Tetrads ****
• In the making of sex cells,
crossing over occurs.
• When crossing over occurs, a
pair (2) of chromosomes form
a tetrad.
• A tetrad is 2 chromosomes (4
chromatids) held together in
the middle by a centromere.
Steps of Meiosis:
A. Interphase
B. Meiosis
1.
2.
3.
4.
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
C. Cytokinesis
5.
6.
7.
8.
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
The second phase of meiosis is
the EXACT same as mitosis,
BUT there are TWO cells
instead of 1
1. Prophase 1
• Chromatin turns to chromosomes
• Chromosomes pair with homologous chromosomes to
form a tetrad
• Crossing over occurs
PROPHASE 1
• Chromosomes
(TETRAD)
• Spindle fibers
• 1 cell
2. Metaphase 1
• Tetrads line up on equator (meta/middle)
METAPHASE 1
• Tetrads
• In middle (meta/middle)
• 1 cell
3. Anaphase 1
• Tetrads pull apart into chromosomes
• Move to opposite poles
ANAPHASE 1
• Tetrads separate into
chromosomes
• 1 cell
4. Telophase 1
• Chromosomes are at opposite ends
• Cleavage furrow present
• 2 new cells have formed
TELOPHASE 1
•
•
•
•
Opposite ends
Spindles disappear
Cleavage furrow
1 cell
5. Prophase 2
• Chromatin turns to chromosomes
• Nucleolus disappears
• Nuclear envelope/membrane disappears
• Centrioles move to opposite sides of the cell
• Microtubules form spindles (help split chromosomes)
PROPHASE 2
• Chromosomes
• Spindle fibers
• 2 cells
6. Metaphase 2
• Spindles attach to chromatids
• Chromosomes line up on equator (MIDDLE) of cell
METAPHASE 2
• Chromosomes in middle
• 2 cells
7. Anaphase 2
• Chromosomes are pulled apart into chromatids
ANAPHASE 2
• Chromatids
• 2 cells
8. Telophase 2
• Chromosomes have reached opposite ends of the cell.
• Spindles disappear
• Nuclear envelope/membrane reappears
• 4 nuclei have formed
• Cleavage furrow present
• 4 cells
TELOPHASE 2
•
•
•
•
Opposite ends
Cleavage furrow
Spindles disappear
Almost 4 cells
STUDYING HUMAN
CHROMOSOMES
• Karyotype- an analysis of chromosomes that
photographs and arranges chromosomes from a
somatic cell into homologous pairs.
• The purpose of a karyotype is to determine if there are
any defects (all humans should have 46 chromosomes;
defects would be you have either too many or too few)
2 Types of Chromosomes:
1. Autosomes- ALL
chromosomes except the
ones that determine
gender (22 pair)
2. Sex Chromosomes- one
pair (2 chromosomes)
that determine gender
Female; XX
male; XY
Formation of Sperm & Egg
• Important terms to know:
1.
2.
3.
4.
5.
Ova
Oogenesis
Polar Body
Spermatozoa
spermatogenesis
1. Ova
• Egg cells/female
gametes
2. Oogenesis
• The production of a ova (egg cell)
3. Polar Body
• A cell(s) produced during
oogenesis that does not
produces a mature egg cell
• Smaller
• No organelles
• Basically empty
• 3 polar bodies; 1 mature cell
4. Spermatozoa
• Sperm cells/male gametes
5. Spermatogenesis
• The production of sperm cells
Fertilization
• When a haploid sperm and a
haploid egg form a diploid cell
• Union of male and female
gametes
• In humans: 23 + 23 = 46
• In plants, this is called,
pollination.
Development
• All complex organisms start out as ONE cell called a
zygote.
• The zygote begins to divide by mitosis and turns into a
mass of cells called and embryo.
• Each division doubles the amount of cells.
• After several days of dividing, a solid ball of cells is
formed called a morula (early stem cells)
• The morula divides to form a hollow ball called a
blastocyst.
• After this, the cells differentiate (get their jobs)
Bacterial Conjugation
• A type of sexual reproduction
occurring in bacteria
• Primitive
• Happens when 2 unicellular
organisms exchange genetic
material (DNA).
Advantages
Disadvantages
Asexual (mitosis)
• Large number of offspring • Offspring are genetically
• Quick
identical to parent (limit
• Requires one parent (set of
their chance of surviving in
DNA)
a changing environment)
These things may increase its
chances of survival in a
favorable/stable environment
Sexual (meiosis)
• Not genetically identical to • Produces a small number
parent (helps them adapt
of offspring (fewer may
to changing environment)
survive)
• Requires 2 parents (sets of
DNA)