Why do mitochondria fuse together?

Question

Contrary to all of the textbook images of mitochondria that I have seen over the years, I had just learned that the mitochondria within a cell form a dynamic branching network along microtubule scaffolding by fusing with each other.

Why would they need to fuse together?

When they fuse, would this involve only the outer mitochondrial membrane?

Would it not behoove a mitochondrion to remain distinct from others both physically and genetically?

Answer 1

Mitochondria produce a large quantity of reactive oxygen species (ROS) that damage the mitochondrial genetic material. These cell organelles do have a DNA repair mechanism similar to that of the nucleus to some extent 3 which is not entirely understood however they have multiple copies and so the fusion and fission of mitochondria work together to maintain as many viable/healthy mitochondria as possible.

When two mitochondria fuse, their genetic material can recombine and thus exchange their damaged DNA. In this way, one of them repairs its DNA at the expense of the other accumulating more damaged DNA. Mitochondria that accumulate too much damaged DNA will 'die' - get eliminated, but they can be replaced by fission of healthy ones. Take a look at this wiki page, it has useful info.

Edit: This article may also be useful. (Mitochondrial fusion and division: regulation and role in cell viability Giovanni BENARD and Mariusz KARBOWSKI, Semin Cell Dev Biol. 2009 May;20(3):365-74.)

Answer 2

Mitochondria are granular or filamentous organelle, which are present in the cytoplasm of a cell. They are ovoid in shape, with the presence of double membranes. Mitochondrial fusion is required to distribute mitochondrial DNA to the mitochondrial population and to maintain its respiratory competent and energized organelles. Mitochondrial division is required to efficiently distribute organelles to distal parts of cells.