Mitochondrial diseases Flashcards
What is Leigh disease?
It is the most common mitochondrial disease to occur in childhood. It is a progressive, episodic neurodegenerative disorder that causes motor and intellectual regression. Symmetrical lesions form on either side of the brain.
Are there more mitchondria in slow twitch muscle fibres or fast twitch muscle fibres?
There are more mitochondria in slow twitch muscle fibres, because they use energy from glycolysis for endurance and long-term energy. Fast twitch muscle fibres require faster, explosive energy forms and so they use other sources, not mitochondria.
What is the endosymbiont hypothesis with regards to the origin of mitchondria?
Mitochondria were believed to have been bacterial organisms, that were very good at producing energy from oxygen and sugars. Then, other larger eukaryotes that didn’t have the ability to produce energy from oxygen swallowed mitochondria and incorporated the mitochondrial genome into the eukaryotic genome. The evidence for this is the fact that mitochondria still have their own genome, even as an organelle (heteroplasmy).
Does the mitchondrial DNA that we inherit come from both of our parents?
No. Mitchondrial DNA only comes from our mothers. This is because the egg’s mitochondrial DNA overpowers the mitochondrial DNA of the sperm.
What does mitochondrial DNA encode anyway?
It mainly encodes mitochondrial proteins. There are around 37 mitochondrial DNA genes, but about 1000-1500 different types of these genes in the population.
Can mitchondrial DNA have mutations in it?
Yes, infact mitochondrial DNA is 10 times more likely to mutate than nuclear DNA.
What is the threshold effect with regards to mitochondrial mutation?
The mitochondrial diseases refer to the fact that there is a minimum amount of mutant mitochondrial DNA that must be present before the produced mitochondrial behave abnormally.
what is the mitchondrial DNA bottleneck?
Because the mother has multiple copies of mitochondrial DNA that she can give to her children, and if only some of these have mutation and others don’t, then during oogenesis, some of the eggs she produces will have mutated mitochondrial DNA and others may be spared and inherit normal mitochondrial DNA.
What are some of the therapeutic techniques being used to prevent against mitchondrial mutational diseases?
It is a process called pronuclear transfer, in which a mother with mutated mitochondrial DNA would give her egg, and the husband his sperm. However, the mitochondrial DNA from the mother would be removed and replaced with a clean donor’s mitochondrial DNA. Thus, the process works as a mitchondrial donation, so that the child still has genes from mum and dad, but different mitochondrial dna. This process is still banned in most countries, but England is considering allowing it.
what is Illumina sequencing?
Illumina sequencing enables fluorescently labelled DNA fragments to be amplified and each base pair is identified in order and sequnced.
What is an ion torrent?
An ion torrent is when individual molecules within single wells on a chip are sequenced in reactions that release protons for detection.
