Mitochondiral genetics

Question 1

What is homoplasmy in mitochondria

Answer 1

All copies of mitchondiral genome are the same

Question 2

What is heteroplasmy in mitochondria

Answer 2

More than one type of mitochondrial genome present

Question 3

Why can mitochondrial diseases have nuclear origins

Answer 3

Nuclear proteins are involved in the function of mitochondria

Question 4

Describe the features of a mitochondrial disease caused by nuclear genome mutations

Answer 4

Same inheritance patterns as Mendelian disorders

Caused by defects in genes involved in replication, transcription, translation and repair of mitochondrial DNA

Question 5

How does damage to Parkin/PINK1 pathway lead to parkinsons

Answer 5

Normally PINK1 is imported into the mitochondria, cleaved and released; but damage to mitochondria causes depolarisation of membranes, so PINK1 accumulaties in the outer membrane of MT which cases Parking to be recruited into mitochondria triggering autophagy. Build-up of disfunctional mitochondria

Question 6

What is the link between mitochondrial diseases and cancer

Answer 6

Cancerous tumours produce excess lactte in the presence of oxygen (Warburg effect); high rate of glucose uptake by solid tumours is used for diagnosis; evidence of defective mitochondria

Question 7

What effect does mtDNA have on tumour development

Answer 7

Cells without mtDNA show slower tumour formation