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BF - MM1

Mitochondrial genome and mtDNA disorders

QuestionAnswer
Mitochondria - what role do they play in apoptosis? Release cytosolic calcium (by raising membrane permeability)
Mitochondria - what is the symbiotic hypothesis? The theory that mitochondria are the result of endocytosis of aerobic bacteria (explains double membranes)
Mitochondria - Is the transcription, translation, and protein synthesis the same as the rest of the cell? No - it is specific
Mitochondria - roughly how many in each cell? 100's
Where are the majority of mitochondrial proteins found? Mitochondrial genome
Mitochondrial genome - type of DNA molecules? Circular and double stranded
Mitochondrial genome - 1700 base pairs, so more/less/the same than the cell nucleus? Way less
Mitochondrial genome - Introns/ no introns? No introns (93% coding)
Mitochondrial genome - replicated dependently/ independently from host cell? Dependantly
Mitochondrial genome - associated proteins? No
Mitochondrial genes - How many? (How many light / heavy?) 37 - (28H, 9L)
Mitochondrial genes - what does it dependent on the nuclear genome for? (3) Enzymes for replication, transcription, translation and repair (targeted)
Mitochondrial genes - Wow many oxidative phosphorylation genes does it code for (out of 83)? 13
Mitochondrial genes - Which (oxidative phosphorylation) complex does it not code for? Complex II
Mitochondrial genes - What are the remaining genes coding for (that don't code for complexes)? tRNA's and rRNA's
Mitochondrial genes - How is mitochondrial DNA well organised? tRNA's do double duty. (The spaces between the areas coding for proteins are coding for tRNA's
Mitochondrial inheritance is what? Maternal
Which gender is affected by inherited mitochondrial disorders? Both
Mitochondria - What is homoplasy? A mammalian cell whose copies of mitochondrial DNA are all identical
Mitochondria - What is heteroplasmy? Proportions of mitochondria varying between cells and tissues
Reduction of mtDNA during oogenesis - what is the bottleneck efffect? Reduction in genetic variation
Reduction of mtDNA during oogenesis - what is replicative segregation? Random replication and partitioning of mitochondrial genomes in daughter cells
Mutation in mtDNA - What is the high mutation rate due to? (5) High O2 radicals, no introns, no protective proteins, less efficient replication, no excision repair
Mutation in mtDNA - What kind of mutations? (3) Substitutions, deletions, insertions
Mutation in mtDNA - What happens with age? Accumulate
Pathogenicity of mtDNA mutations - How many mutations described? Over 300
Pathogenicity of mtDNA mutations - Are deletions inherited/ sporadic? Sporadic and not transmitted
Pathogenicity of mtDNA mutations - Are point mutations inherited/ sporadic? Maternal inheritance
Pathogenicity of mtDNA mutations - What are they dependent on? Mutation site
Pathogenicity of mtDNA mutations - What transcriptional/ translational structures can be effected? (2) Polypeptide or RNA
Pathogenicity of mtDNA mutations (threshold for bioenergetic 'energy failure')- What % must be mutant for deletions? 60%
Pathogenicity of mtDNA mutations (threshold for bioenergetic 'energy failure')- What % must be mutant for tRNA mutations? 90%
mtDNA disorders - Rare/ common? Rare (1:10,000)
mtDNA disorders - What does 'clinically heterozygous' mean? Same disease can be caused by a variety of genes/ alleles, therefore individual mutations can cause different diseases
mtDNA disorders - Early/ late onset? Late (ages 20-30)
Clinical features of mtDNA disorders - Muscle? (3) Progressive external opthalmoplegia + ptosis, myopathy (ragged red fibres)
Clinical features of mtDNA disorders - Heart? (2) Cardiomyopathy, conduction
Clinical features of mtDNA disorders - What may irregular heart beat be due to? Decreased ATP
Clinical features of mtDNA disorders - CNS? (3) Transient hemiparesis ( 1 sided muscle weakness) ataxia, seizures
Clinical features of mtDNA disorders - Eye? (1) Pigmentary retinopathy
Clinical features of mtDNA disorders - Ear? Nerve deafness
Clinical features of mtDNA disorders - What is the pathology of 'nerve deafness'? Damage to auditory nerve
Clinical features of mtDNA disorders - Endocrine? (1) Diabetes
Clinical features of mtDNA disorders - Metabolic (1)? Lactic acidosis
Clinical features of mtDNA disorders - What does CPEO stand for? Chronic Progressive External Opthalmoplegia
Clinical features of mtDNA disorders (CPEO) - Most common type of what type of mtDNA disorder? Oxidative phosphorylation disorder
Clinical features of mtDNA disorders (CPEO) - It is usually benign, what are sympotoms? (3) Fatigue, ptosis, loss of eye movement
Clinical features of mtDNA disorders (CPEO) - What is it a result of in the genome? Single deletion
Clinical features of mtDNA disorders (CPEO) - What is Kearns sayre syndrome? Severe subtype of CPEO
Clinical features of mtDNA disorders (CPEO) - Symptoms of Kearns sayre syndrome? Cardiac, ataxia, retinopathy (poor prognosis)
Clinical features of mtDNA disorders (MELAS) - What does MELAS stand for? Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like episodes
Clinical features of mtDNA disorders (MELAS) - Symptoms of encephalopathy? (3) Stroke like episodes (hemiparisis), headache and vomitting, seizures
Clinical features of mtDNA disorders (MELAS) - Does it present in childhood/ adulthood? Both
Clinical features of mtDNA disorders (MELAS) -What gene is mutated in >85% of cases? tRNA(leu)
Clinical features of mtDNA disorders (LHON) - What does LHON stand for? Leber's Hereditary Optic Myopathy
Clinical features of mtDNA disorders (LHON) - What type of vision loss? Subacute bilateral
Clinical features of mtDNA disorders (LHON) - age of onest? Mean = 23 years
Clinical features of mtDNA disorders (LHON) - Males or females more likely? Males (by 2-3x)
Clinical features of mtDNA disorders (LHON) - What kind of mutation? Missense mutation in 1 of at least 4 genes
Clinical features of mtDNA disorders (LHON) - Which oxidative phosphorylation complex is the mutation in? Complex I
Clinical features of mtDNA disorders (MERRF) - What does MERRF stand for? Myoclonic epilepsy with ragged red fibres
Clinical features of mtDNA disorders (NARP) - What does NARP stand for (also it's sympotms)? Neurogenic wekaness, Ataxia, Retinitus pigmentosa
Clinical features of mtDNA disorders: INVESTIGATION - What is seen in the biochemistry? (1) Raised lactate
Clinical features of mtDNA disorders: INVESTIGATION - What is seen in muscle biopsy? (3) Ragged red fibres, Cox -ve, succinate dehydrogenase -ve
Clinical features of mtDNA disorders: INVESTIGATION - In the DNA in leukocytes what is often observed? (type of mutation) Point mutations
Clinical features of mtDNA disorders: INVESTIGATION -In the DNA in muscle what is often observed? (type of mutation) Deletions/ insertions
Created by: benfenner1