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The Cell Cycle and Cancer
AP Biology
Cell Cycle
• Numerous genes control the cell cycle
• They regulate the progression through checkpoints. A sensor
detects faulty or incomplete cell cycle events such as DNA
damage. A signal is sent from the sensor to an effector that can
stop the cell cycle until the problem has been resolved.
Checkpoints
What does the controlling?
• Kinases are enzymes
that add phosphate
groups to proteins
(phosphorylation)
• There are over 500 of
these kinases
• They take phosphates
from ATP and transfer
them to proteins,
changing the shape
(and function)
What does the controlling?
• Often, kinases are
present, but they
must be activated by
attaching to a cyclin,
another protein.
These kinases are
called cyclindpendent kinases, or
Cdks. A Cdk and it’s
cyclin are referred to
as a cyclin-Cdk
complex.
What does the controlling?
• They are the core of
cell cycle control,
triggering or turning
off activities.
• The concentrations of
Cdk and cyclin
usually rise and fall
together in the cell.
• This system keeps
the cell from dividing
when it should not
divide
What is cancer?
• Cancer is the
inappropriate proliferation
of cells
• If the cell checkpoints are
not in place, this
inappropriate proliferation
can occur.
• Too much mitosis!
• Forms a mass or tumor
What causes cancer?
• Mutations in the
genes encoding the
proteins that control
the cell cycle. (genes
that code for the
kinases and cyclins)
• Oncogenes: genes
that have a normal
function, but that
when mutated, may
cause cancer.
Oncogenes
What causes cancer?
• Oncogenes may be
altered by mutagens such
as UV light, chemicals,
radiation, viruses, or a
genetic predisposition
• Typically dominant,
meaning only one of your
two genes must be
mutated to cause the
altered cell functions
What causes cancer?
• Tumor Suppressor
genes: can halt
progression of the cell
cycle.
• If these are mutated, cells
divide when they should
not
• BRCA I is a gene that
produces a protein that
works with other proteins
to repair DNA damage. (a
type of tumor suppressor)
Usually takes a hit in both
types of genes ( and their
resulting proteins to cause
cancer.
Tumor Suppressor Genes