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Genetics and Human Disease > Mitochondrial function and Genetics > Flashcards

Mitochondrial function and Genetics Flashcards

1
Q

What were mitochondria orignally?

A

Bacteria

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2
Q

What is the function of mitochondria?

A

Produce the majority of cellular ATP

Buffers intracellular ca2+

Driver of apoptosis

Enzyme function through iron sulphur clusters

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3
Q

What is the structure of the mitochondria?

A

2 membranes

Outer is permeable

Inner is not

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4
Q

Do mitochondria move?

A

Move around the cell to where they are needed.

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5
Q

How are mitochondria quality checked?

A

Fusion and fission

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6
Q

What are neurons stained with?

A

TMRM

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7
Q

What is the function of Complex V?

A

Pumps hydrogen across the membrane to make a potential gradient.

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8
Q

How is ATP produced?

A

TCA and OXPHOS

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9
Q

What is TCA?

A

Tricarboxylic acid cycle

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10
Q

How big is mtDNA genome?

A

16,569bp

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11
Q

Does mtDNA have introns?

A

NO

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12
Q

What shape is mtDNA?

A

Circular

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13
Q

How many peptides does mtDNA contain?

A

13

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14
Q

How many tRNAs does mtDNA contain?

A

22

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15
Q

How many rRNA does mtDNA contain?

A

2

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16
Q

Where are the peptides inside the mtDNA?

A

They are hydrophobic so they aggregate always inside the inner membrane.

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17
Q

How many nuclear genes does complex I contain?

A

41

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18
Q

How many nuclear genes does complex II contain?

A

4

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19
Q

How many nuclear genes does complex III contain?

A

10

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20
Q

How many nuclear genes does complex IV contain?

A

10

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21
Q

How many nuclear genes does complex V contain?

A

14

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22
Q

How many mitochondrial genes does complex I contain?

A

7

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23
Q

How many mitochondrial genes does complex II contain?

A

none at all

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24
Q

How many mitochondrial genes does complex III contain?

A

1

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25
Q

How many mitochondrial genes does complex IV contain?

A

3

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26
Q

How many mitochondrial genes does complex V contain?

A

2

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27
Q

What is the name of complex I?

A

NADH Dehydrogenase

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28
Q

What are the 7 constituents of Complex I?

A

MTND1,2,3,4,4L,5,6

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29
Q

Where is the MTND6 encoded?

A

On the light strand.

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30
Q

Where is the heavy strand on mtDNA?

A

Outside circle, has way more genes on it

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31
Q

Where is the light strand?

A

Inner circle of mtDNA.

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32
Q

What is the name of complex II?

A

Succinate Dehydrogenase

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33
Q

What is different about complex II?

A

Doesn’t contain any mtDNA, only nuclear DNA,

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34
Q

What is the importance of complex II?

A

Important in disease diagnosis.

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35
Q

What is the name of complex III?

A

Coenzyme Q or Cytochrome C reductase

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36
Q

Which mtDNA gene is present in complex III?

A

MTCYB

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37
Q

What is the name of complex IV?

A

Cytochrome C Oxidase

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38
Q

Which mtDNA genes are present in complex III?

A

MTCOI,II,III

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39
Q

What is the name of complex V?

A

ATP synthase

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40
Q

Which mtDNA genes are present in complex V?

A

ATPase 8 and 6

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41
Q

What is the function of tRNA in mtDNA?

A
  • ‘punctuate’ mtDNA protein-coding genes

-Important for RNA processing

-required for protein synthesis

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42
Q

What is the definition of polycistronic?

A

Relating to the transcription of two or more adjacent cistrons into a single messenger RNA molecule.

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43
Q

What is special about protein encoded genes?

A

They have tRNA on either side.

44
Q

What is the function of rRNA in mtDNA?

A

Required for mt protein translation

45
Q

Why is rDNA required for mtDNA translation?

A

Translation of mt proteins is internalised, so mtDNA encodes its own ribosomes

46
Q

What kinds of subunits does the rRNA in mtDNA have?

A

Small 12s MTRNR1

Large 16s MTRNR2

47
Q

Where does the replication start for the heavy strand?

48
Q

Where does the replication start for the light strand?

49
Q

What is the D-loop (displacement loop)?

A

The only non-coding region on mtDNA

50
Q

What is the function of D-loop?

A

Important regulatory region

51
Q

How does the D loop regulate?

A
  • Replication Initiation (OH)
  • Transcription Initiation
52
Q

Where within the d loop does transcription start on the heavy strand?

53
Q

Where within the d loop does transcription start on the light strand?

54
Q

How is mtDNA inherited?

A

Maternally inherited

55
Q

Why is mtDNA only inherited maternally?

A

Sperm mitochondria degraded by autophagy.

56
Q

How many copies of mtDNA do oocytes have?

A

Up to 100,000s

57
Q

What is a benign mtDNA variation?

A

Do not affect function.

58
Q

Why does the amount of mtDNA matter?

A

Amount of mtDNA affects cell function

59
Q

What is heteroplasmy?

A

Ratio of wild-type to mutant mtDNA genomes.

60
Q

What is the affect of heteroplasmy?

A

Mutations tend be very recessive but an accumulation over time can become a defect.

61
Q

How is the affect of mtDNA tested?

A

Compare complex II (no mtDNA) to the function of complex IV?

62
Q

Why does the level of heteroplasmy differ from cell to cell?

A

Random segregation of mitochondria during mitosis

63
Q

Why is there a difference of heteroplasmy between siblings?

A

Different heteroplasmy in oocytes, the bottle neck theory.

64
Q

What is mtDNA clonal expansion?

A

Through segregation over time mutations can increase or decrease.

65
Q

What is mtDNA turnover?

A

Really highW

66
Q

Where does mtDNA clonal expansion happen?

67
Q

Why does mtDNA clonal expansion occur?

A

Due to uneven segregation.

68
Q

What stops mtDNA replicating?

A

Ethidium bromide

69
Q

How does ethidium bromide stop mtDNA replication?

A

Ethidium bromide (EtBr) is an intercalating agent, which binds tightly to mitochondrial DNA (mtDNA) during replication, and so blocks the function of mitochondria.

70
Q

What is the function of large scale deletions?

A

Produce smaller genomes which have a replicative advantage.

71
Q

Why is a smaller genome a replicative advantage?

A

They can replicate faster, this is bad or good.

72
Q

What are tetatomas?

A

They are injected into animals then from a 3 germ layers all from a human body.

73
Q

Why does the absence of iron sulphur lead to clonal expansion?

A

There is no membrane potential in the absence of iron sulphur, deletion leads to a high level of division, no OXPHOS, and therefore heteroplasmy.

74
Q

How do point mutations lead to clonal expansion?

A

Accumulate by genetic drift leads to clonal expansion.

75
Q

How does ageing lead to mtDNA mutations?

A

Accumulation of mtDNA mutations occurs with age

76
Q

Why does ageing lead to mtDNA mutations?

A

mtDNA susceptible to damage by ROS

77
Q

What is ptosis?

A

Eyelid muscle weakness

78
Q

What is ptosis caused by?

A

Wide arrange of gene mutations nDNA and mtDNA.

79
Q

Which mitochondrial disorder is the most common?

80
Q

What is m.3243 A>G?

A

Mutation in tRNA leucine (UUR)

81
Q

What does m.3243 A>G lead to?

A

Inefficient translation

82
Q

Which protein tends to be most effected by m.3243 A>G?

A

Complex I deficiency

83
Q

Can you predict inheritance from mother?

A

No inheritance is random.

83
Q

Why are mitochondrial diseases variant in severity?

A

Because the amount of affected mtDNA varies.

84
Q

What does m.3243A>G affect most?

A

Muscle function, heart, bladder, and eye.

85
Q

How to check for single scale deletion?

A

Electrophoresis.

86
Q

How do deletions occur in mtDNA?

A

Regions with the same sequence ‘repeat’.

Repeats are complimentary and bind together.

RNA polymerase keeps moving down the mtDNA.

It cuts out the overhang.

Replication is consistent.

87
Q

What does pearson’s syndrome affect?

88
Q

What does Pearson’s disease affect?

A
  • Sideroblastic anaemia
  • Pancreatic dysfunction
89
Q

What are the symptoms of Kearns Sayre Syndrome (KSS)?

A
  • Muscle weakness
  • Ataxia
  • Cardiac block
  • Progressive external ophthalmoplegia
90
Q

What are the symptoms of Chronic progressive external ophthalmoplegia (CPEO)?

A
  • Ptosis
  • Ophthalmoplegia
  • Deafness & weakness
91
Q

Which genes do Multiple deletion disease affect?

A

– POLG
– TWINKLE

92
Q

What is TWINKLE?

A

mtHelicase

93
Q

When do deletions happen in mtDNA?

A

Deletions are not inherited, they are sporadic during embryogenesis.

94
Q

What does mtDNA turnover require?

A

Needs lots of substrate.

95
Q

What is RNR?

A

Ribonucleotide reductase

96
Q

Why was early HIV medication so dangerous?

A

Gave mtDNA depletion due to inhibiting high replication.

97
Q

What is the therapy for mtDNA depletion?

A

Giving analogs in high volumes.

98
Q

What is the issue with analogs?

A

Not very bioavailable and can cause issues after.

99
Q

On average how much of the genome do deletions remove?

100
Q

What are the reproductive options for couples who have mtDNA related issues?

A

Natural conception but with prenatal diagnosis

Preimplantation genetic diagnosis

Egg donation

Mitochondrial donations

101
Q

What is maternal spindle transfer?

A

Placement of spindle from mtDNA affected in donor egg followed by fertilization.

102
Q

What is pronuclear transfer (PNT)?

A

Woman with mtDNA egg is fertilized, pronucleus is removed and place in a healthy woman’s egg.

103
Q

Why is PNT better than maternal spindle transfer?

A

Has a higher success rate

Genetically father’s and mother’s.

104
Q

What is the problem with mtDNA/unaffected transfer experiments?

A

Might take some affected mitochondria which you would implant back.

Genetics and Human Disease (16 decks)

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