Cell Death and Aging

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Cell Death and Aging

• Biology 12

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Cell Death and Aging

• Must consider cell lineage, not cell age.
• Few organisms live their entire life with the
  same cells cells are replaced.
• Why do cells die?

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Cell Aging

• The age of an organism creates internal
  environmental changes that can affect gene
  function.
• All genes do not functional continually instead,
  over time, programmed activation and deactivation
  of genes occurs as the organism develops and
  functions.

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Cell Age not Organism Age

• Red Blood Cells 120 days
• Skin cells 28 days
• Redwood trees cells 30 years old

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Age-Dependent Genetic Traits

• Pattern Baldness - males 20-30
• Duchenne muscular dystrophy 2 to 5 years
• In most cases the nature of the age dependency is
  not understood.

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My Biological Clock is Ticking

• A biological clock regulates the number of cell
  divisions. Each type of cell divides a determined
  number of times.
• Some cells divide more often than others the
  more specialized a cell the less able it is to
  undergo mitosis.

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Why do cells age?

• Three hypothesis re cell aging
• 1. Cell aging is caused by mutation to the
  genetic code. Increased exposure to mutagens
  increased chance of damage to the code.

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Why do cells age?

• 2. Aging genes shut down chemical
• reactions in the body graying hair, turn off
• melanin production (scientists arent sure)
• 3. Aging occurs when cell lineages die out
• basically worn out cells are not replaced.

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Seatwork!

• Read p. 542-545
• Questions 13, 14, 15, 16, 17