Mitochondrial Genome Flashcards
What are the 4 functions of mitochondria?
multicopy genome-
→ Produce ATP
→ Haem synthesis
→ Neurotransmitter synthesis
→ Nucleotide synthesis
What does mitochondrial DNA look like?
Double stranded circular molecule
What does mitochondrial DNA consist of?
Heavy and light strand
How many genes does a mitochondria have?
37
What are the mitochondrial genes for?
→ 13 oxidative phosphorylation protein subunits
→ 22 tRNAs
→ 2 ribosomal RNAs
Does a mitochondria have introns?
No
What is a D loop?
A non coding region where replication and transcription are initiated
How are mitochondria inherited?
Maternally with no recombination
Which of the OXPHOS proteins is not coded for by mitochondria?
→ Succinate dehydrogenase
→ Complex 2
How is mtDNA packaged?
Nucleoids
How are nucleoids arranged?
One or two copies of mtDNA per nucleoid
What acts as a histone protein in mitochondria?
TFAM (transcription factor A)
Where does mtDNA replication start?
Origin of heavy strand (Oh)
Where does mtDNA transcription start?
Heavy strand promoter and light strand promoter
What are the exceptions to the universal genetic code in mitochondria?
→ AUA and AUG code for methionine (isoleucine in nuclear DNA)
→ UGA codes for tryptophan (stop codon in nuclear DNA)
→ AGA and AGG are stop codons ( arginine in nuclear DNA)
What are the haplogroups of mtDNA?
→ M
→ N
→ H
→ L0-L3
What is the most common haplogroup in Europe?
H
Why can mtDNA subdivide humans into discrete haplogroups?
It does not recombine
Describe the origin of mitochondria
1) A primitive eukaryotic cell ingested bacteria
2) The bacteria helped the cell become more complex
3) All bacterial DNA transferred to nucleus
4) Remnant of DNA is mtDNA
Where do the proteins for replication, transcription and translation come from?
They are encoded by nuclear genes and imported into the mitochondria
What are the 4 requirements for replicating mtDNA?
→ Polymerase gamma (POLG) - mtDNA polymerase
→ TWINKLE - mtDNA helicase - unwinds DNA
→ Single stranded binding protein (SSBP) - keeps DNA unwound
→ TFAM - packages and protects mtDNA
What is the composition of polymerase gamma?
→ Heterotrimer
→ One catalytic subunit (POLyA)
→ Two accessory subunits (POLyB)
What does POLyA contain?
3’ to 5’ exonucleases domain to proofread newly synthesized DNA
What is the function of POLyB?
Enhances interactions with DNA template and increases activity and processivity of POLyA