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Clinical Cytogenetics and Molecular Genetics > Mitochondrial Disorders > Flashcards

Mitochondrial Disorders Flashcards

1
Q

The mitochondrial genome is _________ bp

A

16,571 bp

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2
Q

The mitochondrial genome is 16,571 bp, __________and does/does? not contain introns?

A

Circular
Does not contain introns

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3
Q

The mitochondrial genome contains ______ proteins and _______ tRNAs and ______rRNAs

A

13 proteins
22 tRNAs
2 rRNAs

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4
Q

The mitochondrion utilizes over _______ gene products to function with more than _______ in the respiratory chain alone

A

1500 gene products (963 nuclear encoded)
90 (102 nuclear genes) in the respiratory chain

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5
Q

The main function of mitochondria is ________ ____________?

A

oxidative phosphorylation
oxidizing O2 to H2O
Substrate level phosphorylation of ADP

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6
Q

Each glucose molecular can produce ________ ATP (largely respiratory oxidation) and _______ GTP (Krebs cycle).

A

38 (32 in ETC)
2 GTP

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7
Q

Mitochondria are involved in metabolism and energy production as well as ___________ modulation/homeostasis, ________ stress, ______ signaling and ________

A

calcium modulation
oxidative stress
cell signaling (ROS)
apoptosis

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8
Q

Complex ______ is completely encoded by nuclear DNA

A

Complex II (SDH)

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9
Q

Complex ________ contains COX 10, 14, 15, 20 and SURF1

A

Complex IV

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10
Q

The mitochondrial genome is one piece and ______________

A

polycistronic

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11
Q

Does the mitochondrial genome have recombination?

A

No

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12
Q

Mitochondrial DNA replication is ____________

A

Continuous
(irregardless of cell cycle)

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13
Q

The main mitochondrial DNA polymerase is encoded by the __________ (nuclear/mitochondrial) __________ gene

A

nuclear
POLG1
(POLG2 minor role/accessory subunit)

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14
Q

The mitochondrial _________ and ________ RNAs are unique and encoded by mtDNA

A

ribosomal
transfer

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15
Q

Mitochondrial codon usage is unique or the same?

A

Unique

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16
Q

Does mtDNA contain histones?

A

No histones

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17
Q

The mutation rate of mtDNA is ______ to _____ times higher than nDNA

A

6-10x higher

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18
Q

On average, each mitochondria has an average of _______ copies of mtDNA and each cell has _______ mitochondria

A

2.6 copies
750 mitochondria/cell (about 1500 copies per cell)

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19
Q

Mitochondrial ____________ may determine whether the mutation or wildtype phenotype is expressed

A

heteroplasmy
(vs homoplasmy)

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20
Q

The key determinants of mitochondrial disease include _______ inheritance, mitotic ______ segregation, ______-_______ replication, ______plasmy and the _______effect

A

Maternal
passive/independent (segregation)
post-mitotic (replication)
heteroplasmy
threshold (effect)

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21
Q

Oocytes contain ___________ copies of mtDNA while after fertilization each cell contains ~ ____________ copies of mtDNA at the 8 cell stage

A

500,000
~50,000

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22
Q

The typical threshold is generalized as ________ but may be as high as 100% (homoplasmy)

A

70%

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23
Q

Maternal mitochondrial inheritance is ensured by ________ ________ _______

A

paternal mitochondrial elimination (PME)
*delay usually causes embryonic lethality

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24
Q

____% of mitochondrial disease is sporadic

A

75%

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25
Q

Overall prediction of recurrence risk, in the absence of a detected maternal mutation is _______ to _______%

A

10-15%

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26
Q

The carrier frequency of deleterious mitochondrial mutations is 1 in _______?

A

1 in 200

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27
Q

The prevalence of deleterious mitochondrial mutations across all ages is 1 in ____________

28
Q

Mitochondrial biochemical tests are unreliable but include ______, _______ and ________

A

Lactate
GDF15
FGF21
Alanine
———–
methylmalonic acid (SUCLA) -myopathic
3 methylglutaconic acid (non-specific)

29
Q

Leigh’s disease involves which ox phos complexes?

A

I, II, III and IV

30
Q

Neuropathy, ataxia, retinitis pigmentosa syndrome (NARP) involves complex _______ of ox phos

A

V (ATPase 6)

31
Q

The ________ genes are part of complex ______ and involved in pheochromocytomas and paragangliomas

A

SDH (A-D)
Complex II

32
Q

The _______ genes and complex ______ are involved in LHON, MELAS, Leigh’s syndrome and leukodystrophy

A

ND (NADH) 1,2,3,4 and 6
NDUFS (NADH:ubiquinone oxidoreductase) 1,2,4,7,8
Complex I

33
Q

LHON, MERRF, MELAS, Leigh’s disease and NARP are all caused by _______ mutations

34
Q

___________ and _________ syndromes are caused by mtDNA deletion/duplication

A

Pearson
Kearns-Sayre

35
Q

POLG1, DGUOK, MPV17 and TK2 are caused by ______ _______ syndromes

A

mitochondrial depletion syndromes

36
Q

Biopsies or samples collected for mitochondrial disease testing (3-4)?

A

Leukocytes
Fibroblasts
Muscle/nerve
Liver

37
Q

Currently ______ _____ ______ is the preferred testing to rule out a mitochondrial disease

A

whole genome sequencing (WGS)

38
Q

4 vitamin treatments with generally good treatment response in specific mitochondrial diseases?

A
  1. Riboflavin (sensorineural hearing loss - SLC42A2, SLC52A3)
  2. Thiamine (biotin-thiamine BG disease- SLC19A3, TPK1, PDHA1)
  3. Biotin (BTD, HLCS)
  4. Riboflavin (ACAD9, multiple acyl-coA dehydrogenase deficiency (ETFA,ETFB, ETFDH, SLC25A32, FLAD I)
  5. Coenzyme Q ( PDSS1, PDSS2, COQ2, COQ4, COQ6, COQ7, ADCK3, ADCK4, COQ9)

*cyclic panopterin (molybdenum cofactor deficiency MOCS2, MOCS2, GPHN)

39
Q

________ is the most common nDNA gene while _______ is the most common mtDNA gene involved in Leigh’s syndrome

A

SURF1 (complex IV)
ATP6 (also in NARP) - complex V
**also PDH, Complex I genes

40
Q

Disease characterized by basal ganglia and brainstem lesions with respiratory insufficiency and severe hypotonia with classic onset 3-24 mo

A

Leigh’s disease

41
Q

Mitochondrial tRNA is ______ by nuclear genes

A

charged
YARS2, DARS2, LARS2, CARS2 etc.

42
Q

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) is caused by _____ mutations

A

tRNA-Leu
A3243G -80% ** also in CPEO and MIDD
*also T3217C (7.5%) and A3252G(<5%)

43
Q

The _______ mutation in tRNA-Leu can cause MELAS, CPEO and MIDD

A

A3243G
(DHU loop of tRNA)

44
Q

MELAS can be treated with oral/IV _______, citrulline or taurine (NO regeneration)

45
Q

Myoclonic epilepsy and ragged-red fibers with cardiac arrhythmias and lipomas is caused (80-90%) by mtDNA _________ mutations

A

tRNA-Lys
G8344A

46
Q

The _________ mutation in tRNA-Lys can cause MERRF and Madelung lipomatosis (brown fat)

A

G8344A (80-90%)
(TpsiC loop of tRNA)

47
Q

Leber hereditary optic neuropathy (LHON) causes painless central vision loss at 12-30 years with worse phenotype in males and is caused by a complex _______ deficiency

A

Complex I
(ND4 G1178A) - homoplasmic 50-70%

48
Q

LHON is caused by complex I deficiency and most commonly the gene _______ G1178A mutation

A

ND4
NADH-ubiquinone oxidoreductase chain 4 protein

49
Q

LHON is caused by complex I deficiency and most commonly the ________ mutation in ND4 (NADH-ubiquinone oxidoreductase chain 4 protein)

50
Q

Neurodegeneration, ataxia and retinitis pigmentosa is caused by mutations in the mitochondrial ___________ gene and T8993C>G

51
Q

NARP is most commonly caused by the T8993C>G mutation in the mitochondrial ATP6 gene and complex _______

52
Q

NARP is most commonly caused by the _________ mutation in the mitochondrial ATP6 gene and complex V

53
Q

________ __________ is usually fatal and consists of sideroblastic anemia, pancreatic insufficiency, lactic acidosis and myopathy

A

Pearson syndrome

54
Q

_______ ________ consists of retinitis pigmentosis, ptosis (unilateral) and one of the following (cardiac conduction block, CSF protein >100 or cerebellar ataxia)

A

Kearns-Sayre syndrome

55
Q

Pearson and Kearns-Sayre syndromes are caused by large _____ to _______ kb deletions of mtDNA

A

1 to 10 kb deletions

56
Q

Most common mitochondrial depletion syndrome

A

POLG1 deficiency syndrome (AR/AD CPEO, AR Alpers Huttenlocher syndrome AHS)

57
Q

Myopathic mitochondrial depletion syndrome

A

TK2 - thymidine kinase 2

58
Q

4 genes of mitochondrial depletion syndromes with hepatocerebral predominant phenotypes

A
  1. POLG1
  2. MPV17 (originally Navajo) - mitochondrial inner membrane protein
  3. DGUOK (deoxyguanosine kinase)
  4. C10orf2 (Twinkle) - helicase
59
Q

_______ may cause liver dysfunction in AR POLG1 (AHS)

60
Q

__________ and _________ genes are mitochondrial depletion syndromes with early progressive liver disease

A

DGUOK and MPV17
deoxyguanosine kinase and mitochondrial inner membrane protein

61
Q

_________ is a mitochondrial depletion syndrome caused by mutations of TYMP

62
Q

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a mitochondrial depletion syndrome caused by mutations of _______

A

TYMP
thymidine phosphorylase

63
Q

6 genes of mitochondrial depletion syndromes

A
  1. POLG1
  2. MPV17 (originally Navajo) - mitochondrial inner membrane protein
  3. DGUOK (deoxyguanosine kinase)
  4. C10orf2 (Twinkle) - helicase
  5. TYMP
  6. RRM2B
64
Q

Mutations in _______ cause hypotonia, severe encephalopathy, tubulopathy and can be associated with MNGIE

A

RRM2B
ribonucleotide-diphosphate reductase subunit M2 B)

65
Q

The mitochondrial tRNA for _________ is involved in MERRF while the mitochondrial tRNA for __________ is involved in MELAS

A

tRNA-Lys MERRF and Madelung
tRNA-Leu MELAS, CPEO and MIDD

Clinical Cytogenetics and Molecular Genetics (20 decks)

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