Tiny Animal Becomes An Organ- Can We Engineer This?


Scientific American: Tiny Genome May Reflect Organelle in the Making

Scientific Amrican is reporting on an organism with the smallest known genome.  So small in fact, that it lacks half the genes thought necessary for life.  This type of mini-creature only exists as a parasite inside th body of a host.  What’s so amazing is the possibility that this is a symbionic relationship and that the tiny creature is evolving into a new form of organelle.

For the non-biology majors here organelles are microscopic structures in a cell that have specialized functions (eg, mitochondria and the nucleus).  The mitochondria are structures that made this evolutionary transformation millions of years ago and which live in every cell in our body.  Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into energy. This process is called aerobic respiration and is the reason animals breathe oxygen. Without mitochondria higher animals would likely not exist because their cells would only be able to obtain energy from anaerobic respiration (in the absence of oxygen), a process much less efficient.

The mitochondrion is different from most other organelles because it has its own circular DNA (similar to the DNA of bacteria not mammals) and reproduces independently of the cell in which it is found; an apparent case of endosymbiosis. Scientists hypothesize that millions of years ago small, free-living bacteria were engulfed, but not consumed, by larger bacteria, perhaps because they were able to resist the digestive enzymes of the host organism. The two organisms developed a symbiotic relationship over time, the larger organism providing the smaller with ample nutrients and the smaller organism providing energy molecules (ATP) to the larger one. Eventually, according to this view, the larger organism developed into the cells like we have (eukaryotes) and the smaller organism into the mitochondrion. 

In humans all mitochondria with their separate DNA are inherited from the mother.  They do not share our DNA.  In fact, the infertility treatment of nuclear transfer was designed to try to give an egg from an older woman the energy production of a young egg (before the FDA outlawed it).

Maybe someday we will be able to engineer this type of transformation and create organelles that will provide additional functions to our cells.


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