Download 10-3 Regulating the Cell Cycle

Regulating the Cell Cycle
• cells have a “clock” with checkpoints along the
way in the cell cycle
• chemical signals tell cells when to start and
stop dividing at these checkpoints
Regulating the Cell Cycle
Cell Cycle Checkpoints
• G1 Checkpoint
–checks growth of cell and conditions
of environment
• if everything is good, then the cell
proceeds to S phase
• if the cell environment does not
require division, the cell may enter G0
Cell Cycle Checkpoints
• G1 Checkpoint
–G0 phase
• extended G1 phase
–cell is neither dividing nor preparing to divide
–some types of cells (nerve and heart muscle
cells) go into G0 and continue to perform their
main functions for the rest of the organism's
life
Regulating the Cell Cycle
Cell Cycle Checkpoints
• G2 Checkpoint
–checks replication of chromatin and
conditions of environment
• if everything is good, then the cell
proceeds to the M phase
Regulating the Cell Cycle
Regulating the Cell Cycle
• M Checkpoint
–checks if chromosomes are properly
aligned during metaphase
• if everything is good, then the cell
completes cell division
Regulating the Cell Cycle
Why is regulating the cell cycle
necessary?
• if problems with DNA are caught, the cell cycle
is halted and the cell attempts to:
– correct the issue
• complete DNA replication
• repair the damaged DNA
– complete apoptosis
Apoptosis
• programmed cell death
– if cells are stressed due to the environment or have
a genetic mutation in the DNA, a sequence of selfdestruction is initiated
• “Cell Suicide”
– one cell dying may save the rest of the organism
Regulating the Cell Cycle
Cell Cycle Genetic Signals
• the cell cycle has a built-in genetic
signals to tell cells when to start and
stop dividing
– proto-onco genes – genes that
encourage cell division
– tumor suppressor genes – genes that
inhibit cell division
Cancer
• a disorder in which some cells lose the
ability to control their own growth
• these cells divide uncontrollably
resulting in a tumor
– tumor – an abnormal growth of tissue, not
necessarily cancerous
Cancer
• involves a loss of control over the cycle,
malfunction of the “brakes”
• the malfunction is caused by a mutation
to proto-onco genes and tumor
suppressor genes (usually multiple)
– Mutation – a change in a cell’s genes
(DNA)
– Oncogenes – mutated proto-onco genes
that stimulate excessive division
Cancer
Cancer and metastasis
Lymphatic System
• a network of lymph vessels and lymph
nodes that is a part of the body’s immune
system
– collects fluid, waste material, and other things
(like viruses and bacteria) that are in the body
tissues
– lymph vessels are a lot like the veins that
collect and carry blood through the body but
instead of carrying blood, these vessels carry
a clear watery fluid called lymph
Lymphatic
System
Lymph Nodes and Cancer
• when cancer cells break away from a tumor,
they can travel to other areas of the body
through either the bloodstream or the lymph
system
• cancer in lymph nodes MAY be a sign that the
cancer has spread (or could spread) through
the lymphatic system to other parts of the body
Metastasis
• spreading of cancer from one area of the body
to another
– typically spreads through blood or lymph
Cancer and Cell Functions
• uncontrolled division can compromise the
function of the tissue where the dividing cells
are located and ultimately may cause death
– quickly-dividing cells spend a large amount of time
in M phase
• cells perform most of their normal functions while in
interphase (G1)
Other Resources
• Pg 126-127 in your textbook
• National Institutes of Health
– (see “Related Links” sections also…)
• National Cancer Institute