mitochondria 90% of atp generated there 10 to 1000s per cell (highest in brain, skeletal muscle,...
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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)
Mitochondrial DNA…the “25th chromosome”?
16,568 bp
• 2 Ribosomal RNAs• 22 Transfer RNAs• 13 Proteins
2-10 copiesper organelle
Figure 12.3
• 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!
Figure 12.4
• Affected females have affected offspring
• Affected males don’t
Called “Maternal Inheritance”
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.
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 !
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)
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
MELAS mutation is in the genefor the tRNA for Leucine
80% of mutations
• reduced protein synthesis• shorter tRNA half-life• no new proteins
< See clumps of deformedmitochondria in arteriesof brain….stroke?
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)
What can you do to prevent Free-Radical damage?
• Get your Vitamins-E and-C and β-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.
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
DNA testing was done on the remains of a Vietnam
soldier who was buried in the Tomb of the Unknowns
at Arlington National Cemetery
Remains of unidentified soldiers from WW I and WW II, Korea & Vietnam
In this case, they did RFLP analysisof DNA from the mitochondria.
Extracted mito DNA from theburied bones and compared
that to the DNA of the supposedmother and siblings
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