Teamwork is the way to get ahead in this world, whether you are making your way up the field in the World Cup, waiting tables, or creating eukaryotic cells. When anaerobic prokaryotic cells learned to cooperate with aerobic pre-mitochondria cells, the eukaryotic cell evolved. This allowed for the development of multicellular organisms like mushrooms, oak trees and us.
Mitochondria are small organelles in each of our cells that create a tremendous amount of energy (ATP) from the things we eat, like sugar and fat. They truly are the furnaces of the cell. And because they used to be a separate bacteria-like organism, they contain their own circular DNA. Not only that, they replicate whenever they want to, regardless of when the cell divides.
The genome of a mitochondria is fairly small, but it contains some important genes. There are certain diseases one can have because of mutations in one of your mitochondrial genes.
Now let's switch gears for a second and think about sperm. Each sperm cell is designed for swimming and delivering it's DNA package to the egg. Sperm need lots of mitochondria in their tail to have enough energy to swim, but they don't really need anything other than DNA in the cell body. By removing all of the unnecessary organelles, they become more streamlined and better able to reach the eggy finish line. So once the sperm fertilizes the egg, none of the male mitochondria enter the cell.
Female eggs are pretty much sitting there waiting for a sexy gamete to come along. They contain all of the organelles you would find in any cell, including mitochondria. That's why the mitochondria of any child will only have the mitochondrial DNA from their mom.
I have 2 older brothers and no sisters, so my mom's mitochondria are in all 3 of us but none of us can pass them along to our children. So my mom's mitochondria will 'die out', so to speak. And the way I metabolize food, I think it's a shame that my children won't get the fantastic Newfie Grant mitochondria.
Monday, June 19, 2006
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3 comments:
this was your most interesting science piece yet dude. I love that the sperm don't get to pass their mitochondria on to the embryo because the mitochondria are physically separated due to their location in the tail. WOW!
Does this mean that mitochondria are evolving on a completely separate tract from the humans that carry them? Do you know if there is any evidence that much evolution is still happening in mitochondria?
oh and check this out: from the article overview:
These data indicate that the mitochondrion arose in a common ancestor of all extant eukaryotes and raise the possibility that this organelle originated at essentially the same time as the nuclear component of the eukaryotic cell rather than in a separate, subsequent event.
Mitochondria do evolve separately from humans, in that there is no mixing of genetic info between the mom and dad. All of the evolution takes place in the form of random mutations, much like bacteria.
Because of this, one can trace maternal lineages as well as compare sub-populations based on the similarities of mitochondrial DNA and the patterns of mutations.
Also, you can find mitochondria (and their DNA) in things that have no nuclear DNA such as hair fragments. This has been used in forensic science to link criminals to homocides or sexual assault cases. The downside is that you can not distinguish between siblings, since they all have their mother's mitochondria.
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