8 Questions
Which DNA Pol gamma subunit is the catalytic subunit?
POLg
What is the function of POLg2 in relation to POLg?
It dimer associates with POLg and stimulates activity and processivity
What is the consequence of DNA Polg having a 10-20X higher error rate than nuclear DNA polymerases?
Higher rate of spontaneous mutations in mitochondrial genome
What is the function of Twinkle helicase in relation to DNA Pol gamma?
It is upstream of POLg
What is the characteristic of mitochondrial DNA replication?
Strands replicated in opposite directions (no lagging strand)
What is the function of TFAM in transcription?
Forms the active transcription site
What does heteroplasmy refer to in the context of mitochondrial genomes?
A mixture of potentially disease variants and non-disease variants
What can result in variable penetrance and expressivity of mitochondrial diseases?
Proportion of disease-causing variants
Study Notes
DNA Polymerase Gamma (POLg)
- POLg1 is the catalytic subunit of DNA Pol gamma.
POLg2
- POLg2 is the accessory subunit of DNA Pol gamma, which enhances the processivity of DNA synthesis by POLg1.
Error Rate of DNA Pol gamma
- DNA Pol gamma has a 10-20X higher error rate compared to nuclear DNA polymerases.
- This high error rate leads to a higher mutation rate in mitochondrial DNA.
Twinkle Helicase and DNA Pol gamma
- Twinkle helicase unwinds DNA in the 5' to 3' direction, allowing DNA Pol gamma to synthesize new DNA strands.
Mitochondrial DNA Replication
- Mitochondrial DNA replication is asynchronous, meaning the leading strand is continuously synthesized, while the lagging strand is synthesized in short, discontinuous segments.
TFAM in Transcription
- TFAM (mitochondrial transcription factor A) binds to mitochondrial DNA, stimulating transcription by unwinding the DNA duplex and recruiting RNA polymerase.
Heteroplasmy
- Heteroplasmy refers to the presence of more than one type of mitochondrial DNA within a cell or individual.
Mitochondrial Diseases
- Heteroplasmy can result in variable penetrance and expressivity of mitochondrial diseases, as the proportion of mutated mitochondrial DNA varies between cells and individuals.
Test your knowledge of mitochondrial DNA replication with this quiz. Explore the role of DNA Pol gamma, its subunits, error rates, and the influence of Twinkle helicase. Understand the unique features of mitochondrial genome replication.
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