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DNA and Mitochondria

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The mitochondrial DNA (mtDNA) is a small circular molecule that codes for some proteins in the respiratory chain and RNA molecules involved in translation of these proteins inside mitochondria. Mitochondria have their own DNA and express their genes to produce proteins active in the electron transport chain. However, most of the proteins they need are encoded in the nucleus of the cell. They need to import most of their proteins to function.

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DNA and Mitochondria

  1. 1. GARRY D. LASAGA DNA & MITOCHONDRIA 1 GARRY D. LASAGA
  2. 2. Mitochondrial DNA  Mitochondrial DNA is typically less than 1% of an animal cell’s DNA population.  Mitochondria contain their own genome in multiple copies.  Mitochondrial genome is distinct from that of the nucleus.  Mitochondria have their own DNA and express their genes to produce proteins in the ETC. 2
  3. 3. 0% 20% 40% 60% 80% 100% Mitochondrial DNA Nuclear DNA 1% 02/03/2018 3
  4. 4. Mitochondrial DNA  mtDNA is double stranded circular DNA molecule  mt DNA contain 37 genes for normal mitochondrial function  13 genes make enzymes involved in oxidative phosphorylation 4
  5. 5. 5
  6. 6. Specific genetic code 02/03/2018 6
  7. 7. Maternal Inheritance of mtDNA  mtDNA is maternally inherited in most species (Gyllesten et al., 1991).  mtDNA is nonrecombinant (Hayashi et al., 1985).  During fertilization, the sperm only contributes its nucleus (23 chromosomes). 02/03/2018 7
  8. 8. 02/03/2018 8 Because of its cytoplasmic location in eukaryotes, mtDNA does not undergo meiosis and there is normally no crossing- over, hence there is no opportunity for introgression of the father’s mtDNA.
  9. 9. The Mitochondrial Genome  16,569 base pairs (bp) in length (16-18 kbp)  Encodes for 37 genes, 13 proteins, 22 tRNAs, and 2 rRNAs  Two general regions: Coding region Control region 9
  10. 10. NUCLEAR DNA MITOCHONDRIAL DNA Found in the nucleus Found in the mitochondria 2 sets of 23 chromosomes Each mitochondria may have several copies of the single mtDNA molecule Maternal and paternal Maternal only Can “discriminate between individuals of the same maternal lineage” Cannot “discriminate between individuals of the same maternal lineage”
  11. 11. NUCLEAR DNA MITOCHONDRIAL DNA Double helix Circular DNA is packed into chromatin DNA is not packed into chromosome 02/03/2018 11
  12. 12. Nuclear DNA vs. Mitochondrial DNA • Nuclear DNA undergoes homologous recombination • Maternal and Paternal DNA are mixed • Mitochondrial DNA does NOT undergo recombination Paternal chromosome Maternal chromosome Offspring inherit mixed chromosomes Circular Mitochondrial chromosome
  13. 13. Mothers pass mitochondrial DNA directly to offspring
  14. 14. D-loop region F PT A S 1 2 3 LS P HS P O H 02/03/2018 14 Human mtDNA contains only one longer region, which is non-coding, and it is called the non-coding region or the control region.  The signature form of mammalian mtDNA is the displacement loop (D-loop) molecule.  It is a three-stranded structure with the nascent leading H strand defining the origin of leading-strand replication (OH).

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