of an animal cell showing sub-cellular components. Image: Messer
Nucleolus, 2. Nucleus, 3. Ribosome, 4. Vesicle, 5. Rough Endoplasmic Reticulum,
6. Golgi apparatus (or Golgi body), 7. Cytoskeleton, 8. Smooth Endoplasmic
Reticulum, 9. Mitochondrion, 10. Vacuole, 11. Cystosol, 12. Lysosome, 13.
Inside the inner membrane of the mitochondrion
lies the DNA, which is organized as several copies of a single, circular
chromosome. Mitochondrial DNA usually comes from the egg only, and
is therefore inherited solely from the mother.
All of the thylacine's mitochondrial genes were revealed by an international
team of scientists (Miller et al. 2009) in a research paper: "The mitochondrial
genome sequence of the Tasmanian tiger (Thylacinus cynocephalus)",
published on 13th January 2009, in the online edition of the journal "Genome
Research". This research marks the first successful sequencing
of genes from the thylacine.
the microscope icon for a magnified view of: mitochondrion.
of a mitochondrion. Image: Mariana Ruiz Villarreal.
The genome team's research relied upon new gene-sequencing technology and
computational methods developed by Webb Miller and Stephan Schuster of
the Pennsylvania State University, Centre for Comparative Genomics &
The new methods involved extracting DNA from the hair of specimens, whereas
previous studies had extracted the DNA from bone. The team's work
revealed that hair is an effective time capsule for preserving DNA over
long periods, and under a wide range of conditions.
The keratinised surface of the hair shaft functions like a sheath protecting
the DNA from bacterial contamination and degradation. Schuster states:
think of hair as a shrine for ancient DNA. It is sealed so well that
not even air or water are able to penetrate the DNA stored inside.
Most importantly, bacteria cannot reach the DNA as long as the structure
of the hair remains sound".