Mitochondrial function and Genetics Flashcards
1
Q
What were mitochondria orignally?
A
Bacteria
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
3
Q
What is the structure of the mitochondria?
A
2 membranes
Outer is permeable
Inner is not
4
Q
Do mitochondria move?
A
Move around the cell to where they are needed.
5
Q
How are mitochondria quality checked?
A
Fusion and fission
6
Q
What are neurons stained with?
A
TMRM
7
Q
What is the function of Complex V?
A
Pumps hydrogen across the membrane to make a potential gradient.
8
Q
How is ATP produced?
A
TCA and OXPHOS
9
Q
What is TCA?
A
Tricarboxylic acid cycle
10
Q
How big is mtDNA genome?
A
16,569bp
11
Q
Does mtDNA have introns?
A
NO
12
Q
What shape is mtDNA?
A
Circular
13
Q
How many peptides does mtDNA contain?
A
13
14
Q
How many tRNAs does mtDNA contain?
A
22
15
Q
How many rRNA does mtDNA contain?
A
2
16
Q
Where are the peptides inside the mtDNA?
A
They are hydrophobic so they aggregate always inside the inner membrane.
17
Q
How many nuclear genes does complex I contain?
A
41
18
Q
How many nuclear genes does complex II contain?
A
4
19
Q
How many nuclear genes does complex III contain?
A
10
20
Q
How many nuclear genes does complex IV contain?
A
10
21
Q
How many nuclear genes does complex V contain?
A
14
22
Q
How many mitochondrial genes does complex I contain?
A
7
23
Q
How many mitochondrial genes does complex II contain?
A
none at all
24
Q
How many mitochondrial genes does complex III contain?
A
1
25
How many mitochondrial genes does complex IV contain?
3
26
How many mitochondrial genes does complex V contain?
2
27
What is the name of complex I?
NADH Dehydrogenase
28
What are the 7 constituents of Complex I?
MTND1,2,3,4,4L,5,6
29
Where is the MTND6 encoded?
On the light strand.
30
Where is the heavy strand on mtDNA?
Outside circle, has way more genes on it
31
Where is the light strand?
Inner circle of mtDNA.
32
What is the name of complex II?
Succinate Dehydrogenase
33
What is different about complex II?
Doesn't contain any mtDNA, only nuclear DNA,
34
What is the importance of complex II?
Important in disease diagnosis.
35
What is the name of complex III?
Coenzyme Q or Cytochrome C reductase
36
Which mtDNA gene is present in complex III?
MTCYB
37
What is the name of complex IV?
Cytochrome C Oxidase
38
Which mtDNA genes are present in complex III?
MTCOI,II,III
39
What is the name of complex V?
ATP synthase
40
Which mtDNA genes are present in complex V?
ATPase 8 and 6
41
What is the function of tRNA in mtDNA?
- ‘punctuate’ mtDNA protein-coding genes
-Important for RNA processing
-required for protein synthesis
42
What is the definition of polycistronic?
Relating to the transcription of two or more adjacent cistrons into a single messenger RNA molecule.
43
What is special about protein encoded genes?
They have tRNA on either side.
44
What is the function of rRNA in mtDNA?
Required for mt protein translation
45
Why is rDNA required for mtDNA translation?
Translation of mt proteins is internalised, so mtDNA encodes its own ribosomes
46
What kinds of subunits does the rRNA in mtDNA have?
Small 12s MTRNR1
Large 16s MTRNR2
47
Where does the replication start for the heavy strand?
D Loop
48
Where does the replication start for the light strand?
OL
49
What is the D-loop (displacement loop)?
The only non-coding region on mtDNA
50
What is the function of D-loop?
Important regulatory region
51
How does the D loop regulate?
- Replication Initiation (OH)
- Transcription Initiation
52
Where within the d loop does transcription start on the heavy strand?
HSP1,2
53
Where within the d loop does transcription start on the light strand?
LSP
54
How is mtDNA inherited?
Maternally inherited
55
Why is mtDNA only inherited maternally?
Sperm mitochondria degraded by autophagy.
56
How many copies of mtDNA do oocytes have?
Up to 100,000s
57
What is a benign mtDNA variation?
Do not affect function.
58
Why does the amount of mtDNA matter?
Amount of mtDNA affects cell function
59
What is heteroplasmy?
Ratio of wild-type to mutant mtDNA genomes.
60
What is the affect of heteroplasmy?
Mutations tend be very recessive but an accumulation over time can become a defect.
61
How is the affect of mtDNA tested?
Compare complex II (no mtDNA) to the function of complex IV?
62
Why does the level of heteroplasmy differ from cell to cell?
Random segregation of mitochondria during mitosis
63
Why is there a difference of heteroplasmy between siblings?
Different heteroplasmy in oocytes, the bottle neck theory.
64
What is mtDNA clonal expansion?
Through segregation over time mutations can increase or decrease.
65
What is mtDNA turnover?
Really highW
66
Where does mtDNA clonal expansion happen?
Blood
67
Why does mtDNA clonal expansion occur?
Due to uneven segregation.
68
What stops mtDNA replicating?
Ethidium bromide
69
How does ethidium bromide stop mtDNA replication?
Ethidium bromide (EtBr) is an intercalating agent, which binds tightly to mitochondrial DNA (mtDNA) during replication, and so blocks the function of mitochondria.
70
What is the function of large scale deletions?
Produce smaller genomes which have a replicative advantage.
71
Why is a smaller genome a replicative advantage?
They can replicate faster, this is bad or good.
72
What are tetatomas?
They are injected into animals then from a 3 germ layers all from a human body.
73
Why does the absence of iron sulphur lead to clonal expansion?
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
How do point mutations lead to clonal expansion?
Accumulate by genetic drift leads to clonal expansion.
75
How does ageing lead to mtDNA mutations?
Accumulation of mtDNA mutations occurs with age
76
Why does ageing lead to mtDNA mutations?
mtDNA susceptible to damage by ROS
77
What is ptosis?
Eyelid muscle weakness
78
What is ptosis caused by?
Wide arrange of gene mutations nDNA and mtDNA.
79
Which mitochondrial disorder is the most common?
LHON
80
What is m.3243 A>G?
Mutation in tRNA leucine (UUR)
81
What does m.3243 A>G lead to?
Inefficient translation
82
Which protein tends to be most effected by m.3243 A>G?
Complex I deficiency
83
Can you predict inheritance from mother?
No inheritance is random.
83
Why are mitochondrial diseases variant in severity?
Because the amount of affected mtDNA varies.
84
What does m.3243A>G affect most?
Muscle function, heart, bladder, and eye.
85
How to check for single scale deletion?
Electrophoresis.
86
How do deletions occur in mtDNA?
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
What does pearson's syndrome affect?
Neonates
88
What does Pearson's disease affect?
* Sideroblastic anaemia
* Pancreatic dysfunction
89
What are the symptoms of Kearns Sayre Syndrome (KSS)?
* Muscle weakness
* Ataxia
* Cardiac block
* Progressive external ophthalmoplegia
90
What are the symptoms of Chronic progressive external ophthalmoplegia (CPEO)?
* Ptosis
* Ophthalmoplegia
* Deafness & weakness
91
Which genes do Multiple deletion disease affect?
– POLG
– TWINKLE
92
What is TWINKLE?
mtHelicase
93
When do deletions happen in mtDNA?
Deletions are not inherited, they are sporadic during embryogenesis.
94
What does mtDNA turnover require?
Needs lots of substrate.
95
What is RNR?
Ribonucleotide reductase
96
Why was early HIV medication so dangerous?
Gave mtDNA depletion due to inhibiting high replication.
97
What is the therapy for mtDNA depletion?
Giving analogs in high volumes.
98
What is the issue with analogs?
Not very bioavailable and can cause issues after.
99
On average how much of the genome do deletions remove?
1/3
100
What are the reproductive options for couples who have mtDNA related issues?
Natural conception but with prenatal diagnosis
Preimplantation genetic diagnosis
Egg donation
Mitochondrial donations
101
What is maternal spindle transfer?
Placement of spindle from mtDNA affected in donor egg followed by fertilization.
102
What is pronuclear transfer (PNT)?
Woman with mtDNA egg is fertilized, pronucleus is removed and place in a healthy woman's egg.
103
Why is PNT better than maternal spindle transfer?
Has a higher success rate
Genetically father's and mother's.
104
What is the problem with mtDNA/unaffected transfer experiments?
Might take some affected mitochondria which you would implant back.
105
