B2.030 Mitochondrial DNA and Inheritance Flashcards
how many DNA molecules are in each mitochondria?
2-10
describe the mtDNA molecule
16569 nt double stranded, closed, circular
is replication of mtDNA controlled by nDNA?
nooooo, autonomous
describe POLG
nuclear encoded
structurally similar to bacterial DNA polymerase
less accurate than nuclear DNA polymerases
what does mtDNA encode?
13/89 ETC subunits
2 rRNAs
22tRNAs
which tissues have high metabolic/energy demands?
heart (6000 mtDNA)
skeletal (3000 mtDNA)
brain (200 mtDNA)
which tissue has low energy demand?
lung (600 mtRNA)
what is heteroplasmy of mtDNA?
mtDNA sequence heterogeneity at level of: individual mitochondrion cell tissue person
what are some sources of heteroplasmy within mitochondria?
fission and fusion
accumulation of mutations over time
random segregation in mitosis
how does mtDNA mutation rate compare to nDNA mutation rate?
mtDNA is 5-15 times higher
why does mtDNA get so many mutations?
proximity to ETC
limited protection and repair mechanisms
high mutation rate, accumulation of mutations w age
how can you get heteroplasmy among individuals in a family?
genetic bottleneck during oogenesis
mutational load not evenly distributed between eggs
how can you get heteroplasmy among cells?
mitosis in somatic tissue results in an uneven distribution of mutational load in daughter cells
how can you see heteroplasmy among cells on a slide?
SDH stained blue
COX stained brown
COX should cover SDH in healthy mitochondria
loss of COX activity in some cells will appear blue, healthy cells brown
how do you get heteroplasmy among tissues?
inequitable division of mutational load in pluripotent cells at early stages of life
