Transcript 1.2 Cell Lifespan & mutations

1.2 Cell Lifespan & Mutations
Lifespan of Cells
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A cell’s life depends on where it’s located in
the body and what its function is
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ex: a muscle cell lasts 15 years
a blood cell lives for 120 days (4 months)
a cell in your stomach lining lives for 2 days
Cell division happens more often in some
parts of your body than others
The proteins that are made & transported
throughout the cell are responsible for
controlling how long the cell ‘lives’ for
To Divide or Not to Divide
Cell Cycle Checkpoints
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There are ‘checkpoints’ in a cell’s life that
determine if cell will continue to divide or not
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Cell division will not take place if:
1. There are not enough nutrients to support cell growth
2. The DNA has not doubled
3. The DNA is damaged
Cell Division
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Many cells in our bodies have entered the
non-dividing stage where they are no longer
reproducing
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ex: nerve cells, muscle cells, bone cells
Most normal cells will undergo 20-30 rounds
of cell division before dying
apoptosis = programmed cell death
Cell Death
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All cells are pre-programmed
to die at some point (apoptosis)
Some cells die prematurely
from damages that cannot be
repaired
Some other cells commit
“suicide” where cells break
down in an organized way if
the cell is:
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pre-programmed (ex: a fetus’s hands
& feet)
compromised (cell division goes
wrong, cell is infected with a virus, etc.)
What happens when cell
division goes wrong but the
cell doesn’t stop dividing?
Case Studies:
 Sickle Cell Anemia
 Malignant (Cancerous) Tumours
What is a Mutation?
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A change in the genetic code of a cell
Happens by chance
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when DNA is doubling in interphase, sometimes
the order of letters gets mixed up
Can be good or bad
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good = giraffes born with a longer neck reach
leaves higher on a tree, animals with
superior reflexes can better catch their
prey
bad = tumours like cancer, disorders like
Down’s syndrome or muscular dystrophy
Sickle cell anemia
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Is a blood disorder that is hereditary (passed from
parent to child)
Occurs due to a problem during DNA coding of a
certain protein
Known as a frameshift mutation, one extra base pair
is coded for in a special protein called hemoglobin
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the sun was hot  th esu nwa sho t
causes a mix-up in the expression of the gene
gene affected is the protein that codes for hemoglobin
(a substance that binds to oxygen in the bloodstream
to carry it to cells in the body)
a frameshift mutation is like buttoning up your
cardigan using the top button on one side and the
second-to-highest button hole on the other side
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all buttons below are messed up
Some other interesting diddies
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Effects include fatigue, joint pain & jaundice
As with most hereditary diseases, both
parents must carry the gene for SCA in order
for their offspring to get the disease
Sickle-cell anemia affects almost uniquely
African populations
Those with sickle cell anemia (or those that
carry the gene for it) are resistant to malaria
Cancer & the Cell Cycle
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Some cells start dividing normally, but then
mutate so that they ignore the “stop dividing
signs” in the cell cycle
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some cancer cells have been found to produce a
special protein that signals to cells that they don’t
have to stop dividing
in other cancer cells, mutations don’t allow the
host cell to produce or even recognize the
‘suicide’ proteins that signal normal cell death
Rapid, uncontrolled division of cells is known
as a tumour
Name 4 lifestyle factors that could contribute to developing
tumours in the lungs (and ultimately, lung cancer)
Textbook, p. 35
Benign vs. Malignant
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Use p. 30 of your textbook to learn about the
two types of tumours above
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use the info in your textbook to complete the chart
on the back of your worksheet for the 2 types
discuss with a shoulder partner: which of the two
is the ‘better’ option to end up with?