mitochondria 90% of atp generated there 10 to 1000s per cell (highest in

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)

About 90 different proteins make up the Electron Transport Chain

Figure 12.2

Endosymbiosis

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!

Mitochondrial Division

Sperm mitochondriadestroyed once

in egg cell…

Figure 12.4

• Affected females have affected offspring

• Affected males don’t

Called “Maternal Inheritance”

≈ 100,000 mitochondria in an immature egg cell, but only 100 in a mature egg cell

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)

Ophthalmoplegia

Mitochondrial DNA

16,568 bp

Figure 12.3

¼ of chromosomeoften deleted

Free-Radical “atom or molecule with an unpaired electron”

They are very reactive.

Skin aging/wrinkling

Skin aging/wrinkling

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.

Mitochondrial DNA

16,568 bp

Figure 12.3

This region doesn’t code for anything

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

Shot in 1882.

Buried on his parent’sfarm in Missouri.

2000

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

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.

Remains of unidentified soldiers from WW I and WW II, Korea & Vietnam