Cell Life Cycle- 2 major stages
• A.
__________
• What
happens?
• B. _________
What
happens?
Interphase –
Between Mitotic
phases
• How long (relatively
speaking) is this stage?
• What does the DNA
look like at this stage?
• What happens at the very
end of interphase?
Mitosis
• An highly organized
method of replication
creating identical
daughter cells from
one parent cell
• When a cell loses
control of mitosis, a
CANCER may occur
4 Stages of Mitosis
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
Mitosis Animated
Prophase
Chromatid
• EVENTS:
• Nuclear membrane breaks
down
• Chromatin coils into
chromosomes
• Centrioles move apart
• Spindle fibres stretch
across the cell
• Chromosomes eventually
attach to spindle fibres
ONION ROOT TIP
Metaphase
• Spindle fibres
pull the
chromsomes to
line up along
the equator of
the cell
• Chromatids move to
opposite poles of the
cell
Anaphase
Telophase
• The reverse of prophase
• cell membrane starts to
pinch
• nuclear membrane forms
around each set of
chromosomes
• Each has its own nucleus
(and the cell is ready to
divide)
• Chromosomes at
each end of the
pole
• Spindles fibres
disappear
Cytokinesis
• In late
telophase, the
rest of the
organelles …
great animation of
mitosis
Checkpoints in the cell cycle will prevent division if:
– If the cell is short of nutrients
– If the DNA within the nucleus has not been replicated
– If the DNA is damaged
Mutations in genes involving checkpoints can result in an uncontrolled
cell cycle. The result of uncontrolled cell division can = cancer.
• Cancer cells have large, abnormal nuclei
• Cancer cells are not specialized, so they serve no function
• Cancer cells attract blood vessels and grow into tumours.
• Cells from tumours can break away to other areas of the body
Compare and Contrast Asexual
and Sexual Reproduction
-including the outcomes of mitosis
and meiosis
-including methods of asexual and
sexual reproduction
Asexual
Reproduction
• Produces genetically
identical offspring
• Requires only one
parent
• Is fast and efficient
• Does NOT increase
the genetic variation in
the species
Sexual Reproduction
• Produces genetically
unique offspring (new
combinations)
• Requires 2 parents
• Increases the genetic
variation of the species
Methods of
Asexual
Reproduction
• Binary fission
Regeneration
Fragmentation
Vegetative
Reproduction
Grafting
• Insert a scion (twig) of
desired plant onto a
stock of another
• Scion will continue to
grow as the desired
plant
Spore Formation
• Bacteria
• Microorganisms
• Fungi
Budding
• Offspring grows
attached to parent
• Falls off when mature
Human Assisted Cloning:
• More complex plants
and animals have lost
the ability to clone
themselves because
their cells have
become too
specialized.
• However, scientists have discovered how to
assist the creation of clones in complex
organisms.
Human Assisted Cloning – how
it’s done:
Scientists can clone complex organisims for two reasons:
1. Reproductive Cloning: To produce a genetically identical organism
that because it has desirable characteristics.
2. Therapeutic cloning:
To create STEM cells (embryonic) for use in cell
therapy. The stem cells can correct health problems,
because stem cells can develop into any one of our
200 types of body cells!
• Embryonic
Stem cells
can develop
into ANY
kind of cell
in our body.
• Therapeutic cloning - to correct health problems
– Uses stem cells which can be used to replace
cells damaged from injuries or disease
What can we use use stem cells
for?
– Diabetes, spinal injuries, Parkinson’s disease are only a
few that can benefit from stem cell therapy
Animation of
developent
from egg to
fetus (includes
stem cells)
Why is the use of stem cells
considered controversial?
Where else can you get stem
cells?
• Some blood stem cells can be recovered from the
umbilical cord from newborn children
http://www.blood.ca/CentreApps/Internet/UW_V502
_MainEngine.nsf/page/you_can_be_the_one_match_t
o_save_a_life?
A new way
to get stem
cells! (this
example is
combining
gene therapy
with stem
cells!)
The future??
Meiosis
• A highly organized method of producing gametes
(haploid)
Cross-overs – mixing up the gene
pool
Outcomes of Mitosis and Meiosis
• Mitosis Outcomes:
2 identical diploid
cells
• Meiosis outcomes:
4 unique haploid
gametes
Sexual
Reproduction
• Fertilization
• zygote
• Embryo
- Fetus (around 8
weeks when major
organs have
developed)
Factors that may Lead to
Mutations.
• A mutation is defined as a
change in the DNA
nucleotide sequence.
• Changing the nucleotide
sequence may change the
sequence of amino acids
• Changing the a.a.’s may
change the protein (which
is supposed to control a
specific chemical reaction)
Chemical Factors
• Chemicals (ex. PCB’s) can change the genetic
code by reacting with the DNA molecule, changing
the chemical make-up of the molecule.
Biological Factors
• Viruses can change the sequence of nucleotides
by inserting it’s genes into a sequence
Physical Factors
• Radiation is caused by high energy particles
• These particles can literally crash into the DNA
molecule, and cause pieces of the molecule to fall
out. The cell will try to repair the damage –
sometimes GUESSING what the piece that was
missing coded for!
• Other times, the cells simply splices the molecule
back together, and hopes it will work out alright
Positive Mutations
• Sometimes, a change in the DNA sequence
actually improves the function of an enzyme
• Ex. There are some people that are immune to the
HIV virus•
that immunity was caused by some type of
mutation
Neutral Mutations
• Sometimes, a change in the DNA sequence has no
effect – either the amino acid stays the same as it
was, or perhaps that part of the enzyme was not
critical for it’s function
Negative Mutations
• Sometimes, a change in the DNA sequence will
have a negative effect
• Either the enzyme won’t get made at all, or it
doesn’t work properly, or it has a negative effect
on the animal
• Eg. Hemophilia is caused by a mutation on the X
chromosome
Review: Structure of DNA
• A long chain of
nucleotides
DNA uncoiled
• The sequence
of the
nucleotides
determines the
sequence of
Amino acids
linked together
by the
ribosomes
The code
• A long chain of amino
acids makes a protein.
• The sequence of the
amino acids
determines the type of
protein made
Protein folding
• DNA is a long chain
of nucleotides
• Ribosomes “read”
the nucleotide chain
and construct chains
of amino acids based
on the nucleotide
sequence.
• Chains of amino
acids are PROTEINS
So why do our GENES code for
PROTEINS?
• Is that all we are? PROTEINS?
Proteins are ENZYMES
• Enzymes control ALL the chemical reactions in
the body.
• If you know when to make the right enzymes, and
how many to make, you can reconstruct yourself
– from scratch
• All your “GENES” are is instructions on how to
make specific enzymes.
• Mom gave you your “start-up” package with the
first enzymes in it.
• Those enzymes started making more enzymes,
and you started developing.