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BMS > Mitochondrial Genome > Flashcards

Mitochondrial Genome Flashcards

1
Q

Mitochondrial DNA is always passed on from the

A

Mother

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2
Q

Which process in the mitochondria generates ATP?

A

Oxidative Phosphorylation

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3
Q

Does not provide nearly as much ATP as oxidative phosphorylation

A

Anaerobic Phosphorylation

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4
Q

What are the four basic components of the mitochondria?

A
  1. ) Outer membrane
  2. ) Intermembrane space
  3. ) Inner membrane
  4. ) Matrix
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5
Q

The intermembrane space is made up of structural convolutions (fold) called

-The more you have, the more energy you will be able to make

A

Cristae

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6
Q

The oxidative phosphorylation machinery resides in the

A

Intermembrane space

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7
Q

Many of the nuclearly coded proteins residing in the mitochondrial matrix are used for processing

-oxidized within the matrix

A

Foodstuffs

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8
Q

The TCA cycle occurs in the

A

Mitochondrial matrix

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9
Q

Permeable to small molecules but impermeable to large molecules

-contains signaling receptors (Apoptotic receptors)

A

Outer mitochondrial membrane

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10
Q

Contains apoptotic proteins

A

Inermembrane space

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11
Q

Contains transport proteins and is where the electron transport chain takes place.

-It is the ATP synthesizing complex

A

Inner Mitochondrial membrane

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12
Q

Houses the proteins for the TCA cycle, lipid oxidation, transamination, mt DNA, and the mitochondrial protein synthesis machinery

A

Mitochondrial Matrix

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13
Q

Food from our diets (fats, carbs, protein) are metabolized through a process requiring oxygen to generate large amounts of

A

ATP

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14
Q

Says that mitochondria most likely evolved from engulfed bacteria

A

Endosymbiotic theory

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15
Q

There are two different types of mitochondrial proteins. One type, which is made from genomic DNA, and one type which is made from

A

Mitochondrial DNA

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16
Q

In mitochondria, both fission and fusion occur. The fission process is similar to the

A

Bacterial division process

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17
Q

If you start exercising a muscle, you will undergo

A

Fission

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18
Q

Circular DNA, which is proportional to the ATP requirement of the cell

A

Mitochondrial DNA

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19
Q

Mitochondrial DNA codes for 2

A

rRNAs (16S and 12S)

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20
Q

Codes for 22 tRNAs and 13 proteins

A

Mitochondrial DNA

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21
Q

The proteins that the mitochondria encodes are important for

A

Oxidative phosphorylation

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22
Q

The site where most of mitochondrial replication and transcription is controlled

-Allows replication to move faster

A

D loop (D = displacement)

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23
Q

Can replicate independently of the cell cycle

A

mt DNA

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24
Q

Which DNA polymerase functions in mitochondrial replication?

  • Encoded by the nuclear genome
  • has a proofreading and exonuclease activity
  • more error prone than nuclear DNA polymerases
A

DNA polymerase ƴ

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25
Q

What is the helicase for mtDNA replication?

A

Twinkle

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26
Q

There are over 160 identified mutations that lead to disease in

A

DNA polymerase ƴ or Twinkle

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27
Q

Initiated from promoters generating polycistronic transcripts, which are then processed to produce the individual mRNA, rRNA, and tRNA molecules

A

Mitochondrial Transcription

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28
Q

Mitochondrial transcription requires what three things?

A
  1. ) mtRNA polymerase
  2. ) Transcription acticator (TFAM)
  3. ) Either mtTranscription factor B1 or B2
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29
Q

How many RNA polymerases are required for mitochondrial transcription?

A

1

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30
Q

The molecule that helps initiate mitochondrial transcription

-acts almost like a histone after replication

A

TFAM

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31
Q

When TFAM wraps the mtDNA, it becomes a

A

Nucleoid

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32
Q

Organelles about 1 micrometer in length in the cytoplasm of cells. There are typically 10-200 per cell, but there can be thousands of in a cell with very high-energy needs

A

Mitochondria

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33
Q

A typical lipid bilayer, which is permeable to small

molecules (

A

Outer Mitochondrial Membrane

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34
Q

Is the narrow space between the outer and
inner membranes.

-Houses apoptotic molecules, which lead to cell death

A

Intermembrane Space

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35
Q

Has many infoldings known as cristae, which
increase its surface area.

-A most unusual membrane, in having an extremely high protein content and in being impermeable to small as well as large molecules. Even K+ ions, Ca++ ions, ATP, ADP, protons and OH- groups cannot diffuse through

A

Inner mitochondrial membrane

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36
Q

The site of the electron transport chain and of oxidative phosphorylation

A

The inner mitochondrial membrane

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37
Q

The site of the TCA cycle and fatty acid oxidation.

-There are also small circular mitochondrial DNA molecules (mtDNA), which code for 13 polypeptide chains, which are all subunits involved in oxidative phosphorylation, and also for tRNA molecule and ribosomal RNA molecules.

A

Mitochondrial Matrix

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38
Q

The process of oxidative phosphorylation requires about 100 different polypeptide chains. Of these, 13 polypeptide chains are coded for by

A

mtDNA

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39
Q

Mitochondrial protein synthesis uses the rRNAs and tRNAs coded by the mtDNA, but the ribosomal proteins are all coded for by

A

Nuclear DNA

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40
Q

In the mitochondria, replication, transcription, and translation, are all controlled by

A

Imported nuclear proteins

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41
Q

Double stranded circular DNA, made up of 16,600 bases and no introns

A

Human mtDNA

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42
Q

The two strands of mtDNA differe in base composition. What are the two strands of the mtDNA called? Why?

A
  1. ) Heavy (H) strand: encodes more proteins

2. ) Light (L) strand

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43
Q

mtDNA contains only one significant non-coding region, which is called the

A

D-loop (displacement loop)

44
Q

The site where most of replication and transcription is controlled

A

D-loop

45
Q

Mitochondria replicate many times in their life cycle. They undergo division by

A

Fission

46
Q

mtReplication starts with the H strand origin in the

A

D-loop

47
Q

Binds single stranded DNA in mtDNA replication

A

mtSSB (mitochondrial single stranded binding protein)

48
Q

Regulated at the non-coding D loop

A

Mitochondrial transcription

49
Q

Unique in its ability to bind DNA non-specifically in addition to recognising specific sequences within promoter regions

A

TFAM

50
Q

Packages mtDNA into nucleoids, facilitating
mtDNA replication and transcription, and
provides protection from DNA damage.

A

TFAM

51
Q

Mitochondrial transcription proceeds bidirectionally, giving rise to

A

Polycistronic transcripts

52
Q

tRNA processing enzyme that processes mtRNA

A

RNAse P

53
Q

Human mitochondrial mRNAs have short

A

Poly(A) tails

54
Q

Translation of the 13 polypeptides coded for by mtDNA takes place in the

A

Mitochondrial matrix

55
Q

Is mtRNA capped?

A

No

56
Q

Mitochondrial translation resembles

A

Bacterial translation

57
Q

What are three distinctive features of mitochondrial genetics?

A
  1. ) Very high mtDNA mutation rate
  2. ) Maternal inheritance of mtDNA
  3. ) Random segregation of mitochondria and mtDNA
58
Q

Has a DNA mutation rate that is 10-20 times that of nuclear genes

A

mtDNA

59
Q

Why is mtDNA so prone to mutations?

A

Because of its proximity to oxidative phosphorylation which generates ROS

60
Q

mtDNA also has no introns and little

A

Repair mechanism

61
Q

From person to person, the mtDNA sequence differs on average by

A

4 nucleotides/ 1000 bp

62
Q

The oocyte has a much larger cytoplasmic volume than sperm, so in the fertilized oocyte >99% of mitochondria are contributed by your

A

Mother

63
Q

The small amount of mtDNA contributed by sperm gets

A

Inactivated

64
Q

During cell division, mitosis and meiosis ensure coordinated segregation of chromosomes. However, during mitochondrial biogenesis, fission and fusion lead to a

A

Random distribution of mitochondria and mtDNA

65
Q

When all the mtDNA in a cell are the same, it is known as

A

Homoplasmy

66
Q

When there is a mixture of mutant and normal mtDNA in the same cell, it is called

A

Heteroplasmy

67
Q

Tissues such as cardiac muscle, skeletal muscle, and CNS have very high

-each cell has a threshold level

A

ATP requirements

68
Q

In a heteroplasmic cell, when the number of normal mtDNA drops below the threshold level, the respiration and ATP synthesis of the cell may be insufficient and lead to

A

Cell death

69
Q

The number of mtDNA mutations increases with age
(especially deletions) and as a result, as you age, the levels of oxidative phosphorylation

-Why older people feel more tired

A

Decline

70
Q

It is increasingly clear that some human pathological conditions are caused primarily or secondarily by defects in the process of

A

Oxidative phosphorylation

71
Q

Mutations leading to defects in oxidative phosphorylation can be present either in

A

mtDNA or Nuclear DNA

72
Q

When the inheritance pattern does not follow simple Mendelian inheritance, we can suspect the possibility of a

-Will have a maternal inheritance pattern

A

Defect in mtDNA

73
Q

Because of the random distribution of mtDNA, the mutant mitochondria could exceed the threshold in one tissue in one family member, but not in another as a result, we may see

A

Variability in clinical consequences among family members

74
Q

Maternal inheritance, variability in tissues and among family members, late onset, lactic acidosis, and massive mitochondrial proliferation in myofibers are all clinical features of defects in

A

mtDNA

75
Q

As we age, there is often an increase in the number of

A

Mutant mtDNA

76
Q

The most recognized abnormality in patients with mitochondrial disorders is

A

Lactic acidosis

77
Q

Dysfunction in the ETC causes a decrease in the production of ATP. Low ATP levels result in an upregulation glycolysis, leading to an overproduction of

A

Lactate

78
Q

Massive mitochondrial proliferation in myofibers appear around the mitochondrial periphery as

A

Ragged Red Fibers (RRFs)

79
Q

Often include a large part of the mtDNA genome and affect more than 1 subunit

-increases with age, so the disease usually progresses with age

A

mtDNA deletions

80
Q

Usually spontaneous and sporadic, and have symptoms including: ocular myopathy, lactic acidosis, hearing loss, and dementia

A

mtDNA deletions

81
Q

Kearns-Sayre syndrome, characterized by progressive muscle weakness and retinopathy is an example of a disease caused by

A

mtDNA deletions

82
Q

Base substitution mutations in the tRNA of mtDNA result in characteristic

A

RRFs of mitochondrial myopathy

83
Q

Mutations in the tRNAs usually affect more than one

A

Subunit

84
Q

A base substitution in the mitochondrial DNA (mtDNA) gene encoding tRNALys is the gene most commonly associated with the disease

A

MERRF (Monoclonic Epilepsy and Ragged Red Fiber Disease)

85
Q

This mutation that causes MERRF leads to a reduction in mitochondrial protein synthesis, in particular of complexes I and IV, which have the most mitochondrial encoded subunits

A

A to G substitution at nucleotide 8344

86
Q

A disease characterized by maternal inheritance that is an example of an mtDNA point mutation

A

Leber’s hereditary optic neuropathy (LHON)

87
Q

The death of the optic nerve in LHON results in sudden onset in blindness, and this threshold is crossed when 80-90% of the mtDNA in a cell has the

A

Mutation

88
Q

Which point mutation is the most common cause of LHON

A

Arg to HIS substitution in subunit 4 of NADH dehydrogenase

89
Q

Most of the mtDNA point mutations leading to disease are found in

A

Complex I

90
Q

What are the three different types of mtDNA mutations that lead to disease?

A
  1. ) mtDNA deletions
  2. ) Base substitution mutations in the tRNA
  3. ) mtDNA point mutations in protein coding genes
91
Q

One major source of mitochondrial diseases is a mutation in the nuclear DNA region coding for

A

DNA polymerase ƴ

92
Q

Tumor cells adapt to the requirements of unrestrained growth, in part by shifting from oxidative phosphorylation to glycolysis, known as the

-The decreased oxidative phosphorylation is promoted by defects in DNA polymerase POLγ and in mtDNA.

A

Warburg Effect

93
Q

mtDNA encodes 13 polypeptide chains, which are all part of protein complexes involved in oxidative phosphorylation and are all embedded in the

A

Inner mitochondrial membrane

94
Q

Four of the five mitochondrial complexes contain

A

Mitochondrial proteins

95
Q

During early oogenesis, there is a substantial reduction in the amount of mtDNA present. This is known as the

A

Bottleneck affect

96
Q

There is no mitochondrial division when germ cells are

-results in some cells getting a lot of mutated mtDNA and others getting none

A

Dividing

97
Q

Can not pass mitochondrial diseases to any of their children

A

Affected Males

98
Q

The point at which there are enough mtDNA mutations that we begin to see the phenotypic effect

A

Threshold effect

99
Q

Level of Ox. Phos. decreases with age. When the amount of ATP produced falls below a certain threshold in a given tissue, a phenotype will be observed. This could be due to an increasing number of mutations with age or from

A

Random distribution of mutated mtDNAs

100
Q

Due to heteroplasmy and the threshold effect,
different tissues harboring the same mtDNA mutation
may be affected to different

A

Degrees

101
Q

Most mtDNA related sequences share the features of

A

Lactic acidosis and Massive mitochondrial proliferation (results in RRFs)

102
Q

What two things happen as we age?

A

of mtDNA mutations increases, Ox. Phosphorylation decreases

103
Q

Which organs are more frequently affected by mtDNA mutations?

A

Organs requiring a lot of energy

104
Q

In mtDNA multiple mutations can lead to the same

A

Disease

105
Q

Only 1/3 of mitochondrial diseases have

A

RRFs

106
Q

Leigh Syndrome and LHON have no

A

RRFs

BMS (62 decks)

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