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36 Cards in this Set

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What is polyplasm?
cells have multiple mitochondria which contain multiple copies of genomes
what is heteroplasm?
not all mtDNA is the same
What is the threshold effect?
the phenotypic expression of a pathogenic mtDNA based on the proportion of wild type vs. mutant mtDNA in diffferent tissue… thus the minimum critical number necessary to impair energy metabolism.
What is Mtiototic segregation?
if there is a mutation in mtDNA it may be distributed unequally and a mutant phenotype may be expressed.
What is the mutation rate of mtDNA compared to nuclear DNA?
5-10 times greater
What is a Gomori trichromehistochemical stain and what color is a positive test result for abnormal mtDNA? What does the red indicate?
allows detection of abnormal deposits of mtDNA… red: RRF (ragged red fibers)… red indicated an excess of mtDNA, which is an compensatory measure
What does a ragged-blue-fibers result indicate?
succinate dehydrogenase excess
What type of inheritance accounts for 4/5 of the mitochondrial metaboism disorders? Why?
mendelian… the defects are caused by nuclear DNA, for stubstrate transport and utililization, krebs cycle and oxidative-phosphorylation coupling)
What is the effected mechanism that is affected by mtDNA?
ETC complexes…
What are 3 major modes of genetic defects affecting mtDNA
mtDNA point mutations, mtDNA rearrangements, and defects of intergenomic signalling.
What is genererally affected by mtDNA point mutations?
mitochondrial tRNA
How can point muations of mtDNA be determined?
PCR and RFLP
What are the 3 most common point mutation diseases? And which symptoms are associated with them
MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes), MERRF (myoclonus epilepsy with ragged-red fibers), and NARP (Neuropathy, ataxia, and retinitis pigmentosa)/MILS (maternally-inherited Leigh syndrome)
What is the cause of Kearns-Sayres syndrome?
mtDNA rearrangements
What types of inheritance is shown with mtDNA rearrangements?
It's not… it's sporadic… but deletions show up early in development such that cell population widely affected
What test is used to determine mtDNA rearrangements?
southern blot
what are defects of intergenomic signaling?
mtDNA defected that are caused because nDNA factors that affect replication, transcription and translation
Why is it believed that nDNA plays a role in defects of intergenomic signalling?
mendelian inheritance
What are the two most seen clinical manifestation of mitochondrial diseases?
CNS and skeletal and heart muscle… usually multi-systems in tissues with high ATP requirements
What are the pedigree characteristics of mitochondrial inheritance,.
passed on from the mother only to both males and females
what is homoplasmy?
where all mtDNA is the same
What are the symptoms associated with MERF?
myoclonus, seizures, myopathy, cerbellar ataxia
What are VER (visual evoked responses) associated with?
MERRF
what is anaerobic threshold?
it's a measure of muscle capcity to perfomr oxidative phophorylation before lactic acid begins to accumulate in the body
Which mitochondrial disease is associated with sensory neuropathy, ataxia, retinitis pigmentosa, dementia, reduced fetal movemnts developmental delay, and abnormal EEG?
NARP/MILS
Which has the worse mutation load, NARP or MILS?
Moderate: NARF is 70%, High: MILS is 80-90%
What explains differences in mitochondrial disease expression?
mutation load
T/F MILS and NARP coexist in the same family.
TRUE
How is aminoglycoside induced deafness (AID) caused?
a mutation in some mitochondria causes it to (like some bacteria) interact with aminoglycosidease, by interfering with mitochondrial translation
Which disease causes large-scale deletions?
Kearns-Sayre Syndrom
What are disease associated with the nuclear genome?
carnitine cycle enzymes, Krebes cycle enzymes, and coenzyme Q deficiencies
What are 5 sites of carnitine cycle defects?
transporter, CPT I deficiency, carnitine-acy carnitine translocase, and CPT II deficiency
What are the 4 clinical manifestations of transporter deficiencies associated with the transporter? (which is the hallmark symptom)
cardiomyopathy (hallmark), hyptonia (weakness), failure to thrive, and hypoketotic hypoglycemia
What is the genetic cause of carnitine transporter (OCTN2) deficiencies?
stop codons on chr 5
Which enzymes have been implicated in Kreb's cycle deficiencies?
∂-ketoglate dehydrogenase, fumarase, and succinate dehydrogenase deficiency
What are the clinical manifestation of CoQ deficiencies?
Myopathy, ataxia, and encephalomyopathy with renal failure