Lecture 15: Mitochondrial Genetics

Question 1

Mitochondria and chloroplasts contain

Answer 1

DNA

Question 2

Endosymbiotic theory of the origin of mitochondria/chloroplasts

Answer 2

• 1-1.5B years ago, anaerobic eukaryotic cell engulfed an aerobic eubacterial cell through endocytosis
• The aerobic endosymbiont evolved into mitochondria (animals)
• Endocytosis of a photosynthesizing eubacterium led to the evolution of modern eukaryotic cells with mitochondria and chloroplasts (plants)

Question 3

Endosymbiotic theory proposes that

Answer 3

Mitochondria and chloroplasts were once free living bacteria

Question 4

Do mitochondria/chloroplast DNA contain histones

Answer 4

No

Question 5

Mitochondria grow by

Answer 5

Binary fission

Question 6

Mitochondria are heteroplasmic cells which means

Answer 6

Organelles segregate randomly

Question 7

MERFF syndrome

Answer 7

Ragged red fibers
Clumps of diseased mitochondria aggregate
Progressive myoclonic epilepsy
Short stature

Question 8

LHON

Answer 8

Degeneration of retinal ganglion cells

Question 9

Other mitochondrial DNA mutation diseases

Answer 9

NARP
KSS- paralysis of eye muscles
CEOP- Childhood epilepsy
Leigh syndrome- Degeneration of CNS

Question 10

Mitochondrial DNA mutation disease in plants can cause

Answer 10

Cytoplasmic male sterility

Question 11

Petite phenotype

Answer 11

Caused by mutations in mitochondrial DNA rendering cells unable to grow on nonfermentable carbon sources such as glycerol

Question 12

Human mtDNA encodes

Answer 12

16,569 base pairs
2 rRNAs
22 tRNAs
13 proteins

Question 13

Yeast mtDNA compared to human

Answer 13

Five times as large, contains much more non coding DNA

Question 14

What results in varying DNA size in plant mitochondria

Answer 14

Direct repeats that cause looping/pairing

Question 15

Mutation rate of mtDNA vs regular

Answer 15

Much higher mutation rate (5-10x greater)

Question 16

Mitochondria and senescence

Answer 16

Mitochondria are necessary for the pro-inflammatory phenotype of senescence
Mitochondrial biogenesis stabilizes senescence via positive feedback loop involving ROSpecies

Question 17

When do mitochondrial diseases typically arise

Answer 17

Middle age or later

Question 18

Leigh syndrome

Answer 18

Mutations in nuclear or mitochondrial DNA that cause LOF of mitochondria

• Degeneration of CNS
• Clinical onset at 3m-2years

Question 19

Pronuclear transfer

Answer 19

Nuclei from healthy donor egg is replaced by nuclei from mothers egg who has leigh syndrome. Donor egg now has mother nucleus but healthy mitochondria remains from donor egg

Question 20

Many traits associated with chloroplasts exhibit what type of inheritance

Answer 20

Cytoplasmic

Question 21

Unassigned open reading frame refers to

Answer 21

An apparent protein encoding gene - a sequence with a translation start and stop signal in same reading frame - for which a protein has not yet been identified