Download Cancer and Cell Division

Aim: How is the cell cycle regulated?
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1.Worksheet
HW: Study for test on Thursday
HW due on Thursday
Research Paper due on 11/4/2015
A Cell’s Life Cycle
Figure 3–23 The Cell Life Cycle.
The Cell Cycle
• Most of a cell’s life is spent in a nondividing state
(interphase)
• Body (somatic) cells divide in three stages
– DNA replication duplicates genetic material
exactly
– Mitosis divides genetic material equally
– Cytokinesis divides cytoplasm and organelles
into two daughter cells
A Cell’s Life Cycle
Figure 3–23 The Cell Life Cycle.
A Cell’s Life Cycle
• Interphase
– The non-dividing period
• G-zero (G0) phase—specialized cell functions only
• G1 phase—cell growth, organelle duplication, protein
synthesis
• S phase—DNA replication and histone synthesis
• G2 phase—finishes protein synthesis and centriole
replication
• Mitosis Duplicated DNA divides into two sets of chromosomes
Control of Cell Destiny
•MPF- Maturation promoting factor (MPF)
–Signal that induces cell division.
–Consists of group of enzymes called cdc2 proteins (and
proteins called cyclins.
•Cyclins build up during interphase and then
activates cdc2 proteins which activates MPF which
results in cell division.
•Apoptosis
–Programmed cell death
Tumor Suppressor Genes
• Produce proteins that normally inhibit cell
division.
– Loss or alternation of p53 gene leads to
breast cancer, colon cancer, and other
tumors.
– Normal p53 gene protein arrests a cell in
G1 which prevents cell division.
• Repair of damaged DNA and induces
apoptosis in the cells where repair was
not successful
Oncogenes
• Most oncogenes are mutations of certain
normal genes called proto-oncogenes.
• When a proto-oncogene mutates (changes) into
an oncogene, it becomes a "bad" gene that can
become permanently turned on or activated
when it is not supposed to be.
• A defective cell will divide an not undergo
apoptosis.
Centrosome:Centrosome:
Centrioles Centrioles
PericentriolarPericentriolar
material
material
11
6
LM
Nucleolus Nucleolus
Nuclear envelope
Nuclear envelope
Chromatin Chromatin
Plasma membrane
Plasma membrane
Cytosol
Cytosol
all atLM
700x
all at 700x
(a) INTERPHASE
(a) INTERPHASE
2
2
Kinetochore
Kinetochore
Mitotic spindle
(microtubules)
Mitotic spindle
(microtubules)
Fragments of
nuclear envelope
Fragments of
nuclear envelope
Centromere
Centromere
Chromosome
Chromosome
(two chromatids
(two chromatids
joined atjoined at
centromere
centromere
Early
(f) IDENTICAL CELLS IN INTERPHASE
5
5
(b) PROPHASE
(b) PROPHASE Late
Late
Metaphase
Metaphaseplate
plate
3
Cleavage furrow
Cleavage furrow
3
(c) METAPHASE
(c) METAPHASE
4
(e) TELOPHASE
4
(e) TELOPHASE
Cleavage
furrow
Cleavage
furrow
Chromosome
Late
Early
Late
(d)
(d)ANAPHASE
ANAPHASE
Chromosome
Early
Tumors and Cancer
Figure 3–26 The Development of Cancer.
Copyright © 2009 Pearson
Education, Inc., publishing
as Pearson Benjamin
Cummings
Regulating the Cell Life Cycle
• Normally, cell division balances cell loss
• Increased cell division
– Internal factors (M-phase promoting factor, MPF)
– Extracellular chemical factors (growth factors)
• Decreased cell division
– Repressor genes (faulty repressors cause cancers)
– Worn out telomeres (terminal DNA segments)
Mitotic Rate
– Rate of cell division
• Slower mitotic rate means longer cell life
– Muscle cells, neurons rarely divide
– Exposed cells (skin and digestive tract) live
only days or hours.
Copyright © 2009 Pearson
Education, Inc., publishing
as Pearson Benjamin
Cummings
Tumors and Cancer
• Cancer develops in steps
– Abnormal cell
– Primary tumor
– Metastasis
– Secondary tumor
Copyright © 2009 Pearson
Education, Inc., publishing
as Pearson Benjamin
Cummings
Summary
•
•
•
•
Why is interphase important to a cell?
Distinguish mitosis and meiosis.
Define apoptosis
Why are tumor suppressor genes important?
Regulating the Cell Life Cycle
Copyright © 2009 Pearson
Education, Inc., publishing
as Pearson Benjamin
Cummings