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Moreover, nuclear DNA genes involved in aerobic respiration and in mitochondrial DNA replication and transcription were either absent or present only as pseudogenes. This is the first multicellular organism known to have this absence of aerobic respiration and live completely free of oxygen dependency. [20] [21]
Replication of the mitochondrial DNA can occur in two different ways, both starting in the D-loop region. [3] One way continues replication of the heavy strand through a substantial part (e.g. two-thirds) of the circular molecule, and then replication of the light strand begins.
The Mitochondrial DNA Polymerase (Pol gamma, encoded by the POLG gene) is used in the copying of mtDNA during replication. Because the two ( heavy and light ) strands on the circular mtDNA molecule have different origins of replication , it replicates in a D-loop mode .
D-loop replication is a proposed process by which circular DNA like chloroplasts and mitochondria replicate their genetic material. An important component of understanding D-loop replication is that many chloroplasts and mitochondria have a single circular chromosome like bacteria instead of the linear chromosomes found in eukaryotes.
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
In general, mitochondrial DNA lacks introns, as is the case in the human mitochondrial genome; [144] however, introns have been observed in some eukaryotic mitochondrial DNA, [146] such as that of yeast [147] and protists, [148] including Dictyostelium discoideum. [149] Between protein-coding regions, tRNAs are present.
Mitochondrial DNA is a main source of this extrachromosomal DNA in eukaryotes. [5] The fact that this organelle contains its own DNA supports the hypothesis that mitochondria originated as bacterial cells engulfed by ancestral eukaryotic cells. [6] Extrachromosomal DNA is often used in research into replication because it is easy to identify ...
Mitochondrial fission is coordinated with the mitochondrial DNA replication process. [2] Some of the proteins involved in mitochondrial fission have been identified, and mutations in some of these proteins are associated with mitochondrial diseases. [3]