Transcript Lorem Ipsum - Tri-County Technical College

Mitosis--Cell Copying
Bio 100
Tri-County Technical College
Pendleton, S. C.
Ye ole cell division
• Cell division simply means one cell
dividing to become two cells
• Process can have varied purposes and
results
• 1. Can be a form of reproduction
• 2. Replacement of lost or damaged cells
• 3. Growth and maturation
• 4. Production of special types of cells
Let me answer this one, Doc!
• Asexual reproduction DOES NOT
INVOLVE the formation of gametes (sex
cells)
• Sexual reproduction DOES involve the
formation of gametes
• How those gametes are gotten together is
another story and can be a real hoot!
DNA in varied forms…
• In eukaryotes, the DNA (genetic material)
of a nondividing cell occurs in string-like,
unwound form called CHROMATIN
• Prior to cell division, the chromatin
condenses and super-condenses into
chromosomes
• Only difference between chromatin and
chromosomes is their FORM (arrangement)
Let me see that again
Chalk talk time on the composition of an
eukaryotic chromosome
It is composed of two SISTER
CHROMATIDS joined at location known as
CENTROMERE
Unless mutation occurred, each contains the
same genetic material (copies of each other)
Intro to Mitosis and Meiosis
• Mitosis and meiosis are terms that describe
“nuclear” division
• Terms apply to eukaryotic cells
• Most prokaryotes utilize binary fission
(fission) for “reproduction”
• Term simply means “splitting in two”
• Copies genetic material and “splits”
forming two cells that are “clones” of
“parent” cell
The Cell Cycle
• The life of a cell can be described
with the cell cycle.
• After going through the cycle a set
number of times, a cell dies.
• Mitosis is a part of the cycle.
Phases of Cell Cycle
• G-1
– first gap phase after mitosis is finished
– DNA components are synthesized
• Synthesis Phase
– DNA is replicated
– chromosomes are replicated
• G-2
– gap phase after DNA replication
Mitosis
• G-1, Synthesis Phase, and G-2 were
considered to be a part of mitosis known as
Interphase
• Interphase
– period of time for Gap-1, S, and Gap-2 phases
– nucleus is not dividing
– cell is getting ready to divide
Prophase
• The chromosomes are replicated by this
time and become visible.
• The nuclear membrane disappears.
• Duplicate chromatids attached at the
centromere
• Centrioles duplicate and move to opposite
poles of the cell.
More on Prophase
• Microtubules are organized into a
spindle
– used to move chromosomes
• Nuclear membrane disappears
• Chromatids become attached to the
spindle fibers at their centromeres
Chromo- somes and -tids
Prophase
Metaphase
• Duplicated
chromosomes
line up single file
in the middle of
the cell between
the two
centromeres.
Anaphase
• The chromatids
are separated
and pulled to
opposite ends
of the dividing
cell by the
spindle fibers.
• “Ana-” means
split
Telophase
• Back to interphase
• nuclear membrane
reforms around each
set of chromomes
• cytoplasm is split
between the new
cells
• chromosomes
disappear
The End Result
• Two cells with the same chromosome
number and genes as the original cell.
• How is genetic information preserved?
– Accurate DNA replication due to accurate base
pairing
• Both cells go into the Gap-1 phase after
telophase.
Cytokinesis
• Mitosis designed to parcel genetic material
• When completed, two identical nuclei in
one cell (excluding any mutation, of course)
• Cytokinesis needed to divide the cytoplasm
and organelles
• Plant cell cytokinesis utilizes formation of
cell plate which will become cell wall
• Animal cell cytokinesis utilizes “cleavage
furrow” for producing daughter cells
• Wonder where they got that name?
To test your understanding of mitosis, sketch a cell with
four chromosomes: one short dark, one short light, one
long light, and one long dark and then carry the nucleus
of the cell through mitosis.
Works so well…but
• A tumor is produced by mitosis gone amuck
• Something happens to the controls that
regulate orderly cell division
• Benign tumor will not spread throughout
body but can still be very dangerous
• Malignant tumor WILL spread to other
locations by METASTASIS
• According to the statistics…will touch
every family in US at one time or another
Naming cancers…
• Named according to where they originate
• Carcinomas originate in external/internal
coverings of the body
• Sarcomas arise in tissues that support the body
(bone/muscle)
• Leukemias and lymphomas are cancers of blood
forming tissues such as bone marrow and lymph
nodes
• Treatments: surgery, radiation, chemotherapy,
holistic, and charlatans