Mitochondria

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• Mitochondria
• 90 of ATP generated there
• 10 to 1000s per cell (highest in
• brain, skeletal muscle, heart,
• kidney, liver)
• About 50 known mutations of
• human mitochondrial DNA

Chapter 12 (pp. 349-354)
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About 90 different proteins make up the
Electron Transport Chain
Figure 12.2
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Endosymbiosis
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• 2 Ribosomal RNAs
• 22 Transfer RNAs
• 13 Proteins

2-10 copies per organelle
Mitochondrial DNA the 25th chromosome?
16,568 bp
Figure 12.3
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• 13 of the 90 Electron Transport Chain proteins
  are encoded by mitochondrial
• DNA.
• The other 77 (plus about 1000 other
  mitochondrial proteins) are encoded by
• nuclear DNA.
• ...So, mitochondria truly are a cooperative
  venture between two genetic systems!

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Mitochondrial Division
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Sperm mitochondria destroyed once in egg cell
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• Affected females have affected offspring
• Affected males dont

Called Maternal Inheritance
Figure 12.4
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100,000 mitochondria in an immature egg cell,
but only 100 in a mature egg cell
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Homoplasmy Same mitochondrial genome in all
tissues of a body.
Heteroplasmy More than one mitochondrial
genome in a body, but can have various ratios in
different tissues.
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Homoplasmy Same mitochondrial genome in all
tissues of a body.
Heteroplasmy More than one mitochondrial
genome in a body, but can have various ratios in
different tissues.
This one is more common !
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• If a mutation occurs in the mitochondrial DNA of
  the mother,
• the severity of the disease in the offspring
  depends on
• Amount of mutant mitochondria inherited by
  child
• Partitioning of mutant mitochondria to
  different tissues of
• the body
• Energy needs of different tissues (higher in
  heart, muscle,
• brain, liver)

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Mitochondrial Encephalomyopathy with Lactic
Acidosis Strokelike Episodes MELAS (pp.
355-357)

• Most common mitochondrial disease
• Recurrent strokes before age of 40
• Myopathy (muscle weakening)
• Lower pH (due to lactic acid build-up)
• Deafness
• Droopy eyelids
• Short stature
• Diabetes

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MELAS mutation is in the gene for the tRNA for
Leucine
80 of mutations

• reduced protein synthesis
• shorter tRNA half-life
• no new proteins

lt See clumps of deformed mitochondria in
arteries of brain.stroke?
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Kearns-Sayre Syndrome KSS (pp. 358-359)

• Ophthalmoplegia (paralysis or weakness of one
  or more
• eye muscles)
• Degeneration of pigment layer of retina
• Cardiac abnormalities
• Neurological abnormalities
• Onset at age 20 (fatal in few years)
• Large deletions (1000s bp) of mito DNA
  duplications
• Is not typically inherited, but rather is
  sporadic (meaning
• it just seems to show up in people)

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Ophthalmoplegia
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¼ of chromosome often deleted
Mitochondrial DNA
16,568 bp
Figure 12.3
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Free-Radical atom or molecule with an
unpaired electron They are very reactive.
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Skin aging/wrinkling
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Skin aging/wrinkling
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What can you do to prevent Free-Radical damage?

• Get your Vitamins-E and-C and ß-Carotene
  (Vitamin-A precursor).
• These are anti-oxidants.

• Regular exercise. Although exercise generates
  free-radicals
• if you do it enough your body responds by
  absorbing them.

• Eat less. Lab rats on limited diets lived 50
  longer, Fruitflies
• lived 30 longer.

• Reduce smoking, drinking alcohol, fatty foods

• Get less sun exposure.

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This region doesnt code for anything
Mitochondrial DNA
16,568 bp
Figure 12.3
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• Mitochondria DNA can be used to study our past
• Maternally inherited only
• No recombination
• Non-coding region collects mutations more
• quickly than nuclear DNA (less of a repair
  mechanism)

Applications Evolution Forensics
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Shot in 1882. Buried on his parents farm in
Missouri.
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2000
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Remains of unidentified soldiers from WW I and
WW II, Korea Vietnam
DNA testing was done on the remains of a
Vietnam soldier who was buried in the Tomb of the
Unknowns at Arlington National Cemetery
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Extracted mito DNA from the buried bones and
compared that to the DNA of the supposed mother
and siblings
In this case, they did RFLP analysis of DNA from
the mitochondria.
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Remains of unidentified soldiers from WW I and
WW II, Korea Vietnam
It matched those of United States Air Force
First Lieutenant Michael Joseph Blassie.
Lieutenant Blassie's remains were returned to
his family in July 1998, and were buried in his
hometown of St. Louis, Missouri.