Mitochondrial Inheritance Flashcards
What does mitochondrial disease refer to?
Mutations in the genome of mitochondria + mutations in the genome of the nucleus that codes for mitochondrial proteins
Describe mitochondrial inheritance
- Autosomal dominant: does not skip generations
- All the children of an affected mother have the disease
- Differences in phenotypes between individuals due to differences and tissue distribution of mutations
What was a consequence of genome fusion?
Many of the mitochondrial proteins are encoded by the nuclear genome, translated in the cytosol and then transferred into the mitochondria
Describe mitochondrial DNA
Circular
No introns
Open
How many genes are there in the mitochondria?
more or less 30
Diseases related to mitochondria affect what predominantly?
Nervous and muscular tissues
What do mitochondrial genes encode for?
Ribosomal RNA [30S: prokaryotic type] and transfer RNA
Difference between mitochondrial and cytosolic protein synthesis
UGA is recognised as a stop codon in the nucleus
UGA is recognised as tryptophan in mitochondria
AUA codes for isoleucine in the nucleus
AUA codes for methionine in mitochondria
How many mutations can take place in mitochondria?
3 mutations
Mutations regarding what can take place in the mitochondria?
- Oxidative phosphorylation
- rRNA synthesis
- tRNA synthesis
Heteroplasmid
Mitochondria within a cell are heterogenous: both mutant and wt
Homoplasmid
All mitochondria are mutated
Heteroplasmy
arises because mitochondria segregate randomly during cell division resulting in different cells containing varying proportions of the 2 types
What does high levels of heteroplasmy refer to?
Cells with high levels of mutant mtDNA
LHON: leber optic atrophy disease
associated with missense mutations in the mtDNA
3 main mutations at basepoints have been identified: MTND1, MTND4, MTND6–> defect in respiratory chain
