the second genome

OB Science Time: The Mitochondrial Genome

Hey guys I know it’s been forever since I posted one of these (hiatus is a struggle, but I can see the light of April 18th on the horizon!!), but it’s finally time for another OB Science Time!!! [crowd cheers] Now I know I have totally talked about this briefly before, perhaps in response to an ask or comment, but it felt about time I make a full post about it, so I am here today to talk to you about the second set of genes in our cells: the mitochondrial genome!

Now as everyone probably knows because we were all forced to memorize this exact phrase, the mitochondria is the powerhouse of the cell! Woo! It is an organelle that produces the majority of the energy used by the cell, so big shout out to the mitochondria. What you may not be as familiar with, however, is the fact that the mitochondria has it’s own genome!! Circular pieces of DNA that encode roughly 37 genes, all for proteins used in the mitochondria (such as mitochondrial tRNAs and proteins that make up the electron transport chain).

How is it possible that an organelle within the cell has it’s own genome? Well way back in the day, millions and billions of years ago, when single-celled organisms ruled the primordial soup, a single cell engulfed another cell, but instead of destroying the cell, they worked together as a team. This team eventually gave rise to basically every other eukaryotic organism, which is why all eukaryotes have mitochondria! Yay!

Another fun fact about the mitochondrial genome: it is inherited maternally. What does this mean? Unlike the chromosomes in your nucleus, which come half from each parent, you only inherit the mitochondria via the original fertilized egg. That means, technically, we are all slightly more genetically like our mothers than our fathers. Don’t tell Dad.

So what does this have to do with Orphan Black? Well, in the cloning process, you have the person who is providing the nuclear genome, but you also need an egg to provide the mitochondrial genome. Now, in cloning of mice in the lab via SCNT cloning (you can read about that here) scientists use one mouse for the nuclear genome and a second mouse for the fertilized egg. This produces more successful results than having the same mouse provide both genomes (so tricky science!!).

So what does that mean for the Leda clones? Did they have an original for the nuclear genome and a separate egg donor for the mitochondrial genome? Did each of the clones receive a separate egg donor? (This would be unlikely, because then they wouldn’t really be clones, they would be almost clones!) and what about the Castor clones? Their original, whoever they are, didn’t have any egg cells, so how did they come up with an egg donor? Was it someone random, someone related to the Castor original, or was it the same egg donor they used for Leda? We may never know the answers to these questions, but it’s interesting to think about.

As always if you have any questions, comments, or desires to continue the conversation, my ask is always open :D and you can check out the rest of OB Science Time here!!!