Download Genetic Control of Protein Synthesis, Cell Function, and Cell

CELL REPRODUCTION
MITOSIS IS CELL DIVISION
• GROWTH
• CELL REPAIR
• NOT MEIOSIS
• GOAL IS TO MAKE IDENTICAL CELLS
• CELLS DO NOT DIVIDE ALL THE TIME
• MITOSIS IS A VERY SHORT PERIOD
• MOST OF THE TIME IS INTERPHASE
Genetic Control of Cell Reproduction
LIFE CYCLE OF THE CELL:
M phase:
• mitosis
• cytokinesis
M
(mitosis)
G2
(Gap 2)
G1
(Gap 1)
EUKARYOTIC
CELL CYCLE
S phase
(DNA synthesis)
Interphase (>95%):
• G1 phase
Cells that
• S phase (DNA synthesis)
cease
division
• G2 phase
DNA Replication: S phase
• switched on by the cytoplasmic S-phase activator
• Replication is initiated at replication origin and
proceeds in both directions.
• Entire genome is replicated once - further replication
is blocked
• involves DNA polymerase and other proteins that
function to unwind and stabilize the DNA and
“prime” DNA replication of the “lagging” strand.
DNA Replication: S phase
• nucleotides are always added to the 3’ end
(DNA and RNA)
• formation of Okazaki fragments on lagging strand
• “new” DNA is proofread by DNA polymerase
• repairs are made and gaps filled by DNA ligase
Chromosomes and Their Replication
• “New” DNA helices associate with histones to form
chromosomes
• The two chromosomes remain temporarily attached
at the centromere.
• Together, these chromosomes are called chromatids.
•MITOSIS
• REMEMBER PMAT
• PROPHASE
• METAPHASE
• ANAPHASE
• TELOPHASE
•INTERPHASE
• TECHNICALLY NOT PART OF MITOSIS
• DNA IS COPIED (DUPLICATED)
• CENTROSOMES ARE DUPLICATED
•PROPHASE
• CHROMOSOMES THICKEN
•METAPHASE
•FOR MIDDLE
• ANAPHASE
• ”AWAY”
• CHROMOSOMES MOVE TO OPPOSITE SIDE
OF THE CELL
• THEY HAVE SPINDLES
• TELOPHASE
• FOR TWO
Stages of Cell Reproduction
Mitosis: M phase
1. Assembly of the mitotic
apparatus
2. Prophase (A,B,C)
3. Prometaphase (D)
4. Metaphase (E)
5. Anaphase (F)
6. Telophase (G, H)
Figure 3-13
• FILM
Cell Differentiation
Different from reproduction ...
• changes in physical and functional properties of
cells as they proliferate
• results not from the loss of genes but from the
selective repression/expression of specific genes
• development occurs in large part as a result of
“inductions,” one part of the body affecting another
THE CELL CYCLE & CANCER
• GROWING OF CELLS OUT OF CONTROL
CANCER
Dysregulation of cell growth
Caused in all or almost all cases by the mutation or
abnormal activation of genes that encode proteins that
control cell growth and/or mitosis
• Proto-oncogenes: the “normal” genes
• Oncogenes: the “abnormal” gene
• Antioncogenes: genes whose product suppress the
activation of oncogenes
Not all mutations lead to cancer!
What causes these mutations?
• Ionizing radiation: disrupts DNA strands
• Chemicals: “carcinogens”
• Physical irritants: e.g., abrasion of the intestinal lining
• Hereditary “tendencies”: e.g., some breast cancer
• Viruses: so-called “tumor viruses” (particularly
retroviruses)
Q: Why does cancer kill?
A: Cancer cells compete
successfully with normal cells
for limited nutrients