Transcript Cell Division - Chapter 10

Review the Cell Theory
Take one minute and write down the 3 parts to the
Cell Theory
1. All organisms are made up of one or more
cells.
2. All cells carry on their own life activities
3.
New cells can arise only from other living
cells by the process of cell division.
The larger the cell becomes, the more demands the cell
places on its DNA and the more trouble the cell has
moving enough nutrients and wastes across the cell
membrane.
DNA "Overload" – In time as the cell grows larger; the
DNA can no longer serve its increasing needs
Surface Area- to- Volume Ratio
Volume increases faster than the surface area of a
growing cell
The surface area-to-volume will decrease. (causes
problems)
So, surface area to volume is why the cells of an
organism do not grow larger even though the
organism grows much larger and why cells stay
small.
To stay small, cells must reproduce.
2 Basic Types of Reproduction
Asexual reproduction
one parent; offspring is identical to parent
Sexual reproduction
two parents; offspring is not identical to
parents
Overview of Cellular Division- (MITOSIS)
Two processes take place
•Division of the nucleus
•Division of the cytoplasm
Review of the STRUCTURE of the NUCLEUS
•Nucleus is the control center of the cell
•Contains DNA (which is the hereditary material
needed for the synthesis of all components of
each cell )
•DNA is found in chromatins - long thin thread
like material
Structure of DNA
Humans have 46 (23 pairs) of chromosomes
•Double stranded, twisted molecule
•Each strand is connected by hydrogen
bond b/w base pairs
Note: Individual chromosomes are not visible when the DNA is
present as chromatin
Human Karyotype
Amt. of time
spent by a typical
cells in each
state:
G1 – 9 hrs.
S – 10 hrs.
G2 – 2 hrs.
Mitosis – 1 hr.
Life Spans of Various Human Cells
Cell Type
Lining of esophagus
Lining of small
intestine
Lining of large intestine
Red blood cells
White blood cells
Smooth muscle
Cardiac muscle
Skeletal muscle
Neuron
Life Span
2-3 days
1-2 days
Cell Division
Can divide
Can divide
6 days
Less than 120 days
10 hrs. to decades
Long-lived
Long-lived
Long-lived
Long-lived
Can divide
Cannot divide
Many do not
Can divide
Cannot divide
Cannot divide
Most do not
Mitosis
•Two daughter cells produced from one
•New cells genetically identical (to each other –
and also to original cell)
•Reproduction in many one-celled organisms (ex.:
amoeba)
•For convenience, process is described as occurring
in stages or phases.
However, it IS a continuous process with no
interruptions between one phase and the next.
: normal diploid cells always have an even number
of chromosomes.
: At the beginning of cell division, each
chromosome consists of two chromatids.
: Each chromatid contains a single DNA molecule.
: Daughter cells at the end of mitosis are
genetically identical to the original mother cell.
: Daughter cells of meiosis are genetically different
from the original mother cell, and from each other.
Mitosis Summary (IPMAT)
2N
2N
2N
diploid cell –Two copies of each
chromosome. Where do the two
copies come from????
2 identical diploid
daughter cells formed
Interphase“RESTING PHASE"
* Not a part of mitosis; this phase occurs BEFORE
mitosis starts
•nuclear of genetic material (chromatin) are replicated
This is CHROMOSOME REPLICATION
* cells grow in size
* more organelles, nucleic acid, & proteins are
produced
* centrioles also replicate during this phase
* Chromosomes are NOT visible
Why do you think calling this phase the “resting phase” is a misnomer?
CELL IN “INTERPHASE”
centrioles
chromatin
nucleus
Animal cell
Plant cell
Prophase- begins mitosis
1. Chromatin condenses into chromosomes =
sister chromatids which now will become visible
2. Centrioles move to opposite sides (poles) of
the cell
3. Spindle fibers radiate out from centrioles to
form asters
4. Spindles attach to the centromere of
chromosome
5. Nuclear membrane & nucleolus disappear
The structure and the actual picture of a chromosome.
cell in prophase
Metaphase- Meta = middle
Chromosomes lined up on equatorial plane
Draw a cell in metaphase
Anaphase 1. Daughter chromosomes move to opposite poles
probably by shortening of spindle fibers
2. Beginning of cytokinesis (cytoplasmic division) cell
membrane 'pinches'.
3. Centromeres divide, forming separate sister
chromatids
cell in anaphase
Telophase- last phase of mitosis
1. Chromosomes reach poles
2. Chromosomes uncoil to form chromatin
3. Spindles & asters disappear
4. Nuclear membrane forms, nucleolus appear
5. Cytokinesis is completed producing two daughter
cells
6. Basically the opposite of prophase
*cytokinesis – cytoplasm division occurs by
pinching inward of cleavage furrow
final stages of mitosis
Telophase and cytokinesis
Mitosis (in plants)
Plant cell division differs from animal cell
division in 2 ways
1. Plants do NOT have centrioles therefore no
asters (still have spindles)
2. Rigid cell wall prevents cell membrane from
pinching; instead, a cell plate forms which
divides the cell in half
PLANT CELLS
ANIMAL CELLS
Daughter cells contain the
same number of
chromosomes as parent cell
No centrioles present;
Spindle forms
Daughter cells contain the
same number of
chromosomes as parent cell.
Centrioles are present;
Spindle forms
Daughter cells have about
half the cytoplasm of parent
cell
Cytoplasmic division occurs
by formation of cell plate
Daughter cells have about
half the cytoplasm of parent
cell
Cytoplasmic division occurs
by pinching inward of
cleavage furrow
ASEXUAL REPRODUCTION
* Offspring genetically identical to parent & each
other
*generally rapid
* high # of offspring
Types of Asexual Reproduction
BINARY FISSION - parent divides into 2 equal
parts
Ex) bacteria, protozoa, some algae
BUDDINGoffspring buds off the parent, identical division of
nuclear material but unequal division of cytoplasm
Ex) yeast, hydra
Spore Formationsingle specialized cells produced by certain organisms
that when released, germinate and grow and form new
individuals (can be formed sexually or asexually)
Ex) bread mold
Regenerationability of an organism to regrow lost body part
a. Relatively simple animals- starfish, hydra,
earthworm, planaria
b. In humans and other vertebrates, small wounds heal
by regeneration of new tissues to replace damaged
tissues.
Regeneration occurs by mitosis.
Vegetative Reproduction•growing new plants from parts of other plants
a. bulb- short underground stem surrounded by thick
fleshy leaves that contain stored food; tulips, onions,
lilies
b. corm- resemble bulbs but do not contain fleshy
leaves; gladioli, crocuses, water chestnuts
c. tuber- enlarged portion of an underground stem that
contains food; white potatoes
d. runner (stolon)- horizontal stem with buds along the
surface of the ground; grasses, strawberry
e. rhizome- a horizontal stem that grows underground;
ferns, irises, water lilies
Artificial Vegetative Reproduction
a. cutting- stem, leaves, roots used to produce new
individuals
b. layering- a stem is bent over & covered with soil
and new individuals grow
c. grafting- 2 parts of plants are cut & joined together;
roses, nectarines
Stock- part that contains the roots
Scion- added piece on top
Advantages
*production of new entirely new plants that are
genetically identical to the original plant
*development takes less time
*seedless fruit can be grown
*higher yields of fruits or nuts
What happens when mitosis (cell division) does not work
properly and too many cells are made to quickly?
Cancer is a variety of diseases in which cells of the body
multiply without control. Cancer can occur in any of the
several types of cells that make up the body. Malignancy has
been linked with changes in the genetic material of the cells
based on three lines of evidence. The daughter cells of a
cancerous cell are always malignant, indicating cancer is an
inherited property. Chromosome mutations, such as deletions
and translocations, are often observed in cancer cells.
Oncogenes are genes that cause some kinds of cancer. When
oncogenes are turned off they will not cause cancer, but when
they are switched on, this leads to uncontrolled growth of cells
that we call cancer.
Uncontrolled Cell Growth
Cancer – disorder which some of the body’s own
cells lose the ability to control growth.
Cancer does not respond to the signals that regulate
the growth of most cells.
As a result, they form masses of cells called tumors
that can damage the surrounding tissues.
Causes –
Radiation exposure
Smoking
Viral infections
1. High number of cancer cells have a defect in a
gene call p53, which normally halts the cell cycle
until all chromosomes have been properly
duplicated