More Than Just A Meme – The Secrets Behind the Infamous Mitochondria (Part 1)

By Calvin J.

In 1957, the American cell biologist Phillip Siekevitz was the first to describe the mitochondria with his infamous phrase – “the powerhouse of the cell”. But he could have never guessed that over 60 years later the now iconic term would become the butt of an internet meme that defines a generation of young adults.

For those who aren’t familiar with the meme or with the biological concept, the mitochondria is a small compartment found in every one of our cells. Its primary purpose is to generate the energy needed to keep us alive. In the past several years, Siekevitz’s phrase – “powerhouse of the cell” – became popularized by high school teachers across North America as an easy way for students to memorize the concept for their SATs.

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One such example of the popular meme which has been trending on  social media sites such as Tumblr since early 2013.

The term quickly caught on amongst millennials as an internet joke, mocking it as an example of another “useless” fact ingrained onto our minds by our public school system. But as useless as it may seem, the mitochondria is in actuality, a lot more than just a cellular powerhouse; it also a biological history book, keeping a record of our maternal lineage.

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Yes, there’s even a Buzzfeed quiz on the mitochondria. Is there anything millennials can’t turn into a joke? Test your knowledge here.

To understand how the mitochondria came to be what it is today, we have to travel back in time almost 2 billion years when a tiny free-floating bacteria was ingested but not digested by a bigger cell. Think of it as a sort of mutually beneficial enslavement process.  The tiny bacteria, in exchange for protection from the turbulent and treacherous environment of our early earth, it began digesting molecules and producing energy for the host cell. With the added energy production, that cell gained a competitive edge in the brutal arms-race of evolution, eventually evolving into a multitude of higher organisms including mammals, plants, and invertebrates that now dominate our planet. Now termed the Endosymbiotic Theory, the idea was first popularized by the force of nature that is, Dr. Lynn Margulis. Despite how widely accepted the idea is today, most scientists originally thought she had completely “gone off the deep end” when she first attempted to publish her model in 1966. But that’s a whole another story altogether.

 

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The Endosymbiotic Theory. A smaller bacterium is engulfed by a larger host cell. With time, it evolved  into the mitochodria we share today. Image obtained from Schmoop.

But how do our little “powerhouses” keep a record of our maternal lineage? Interestingly enough, in humans, the mitochondria can only be inherited from our mothers. A gift passed from a mother to all of her children. When our early human ancestors left Africa – the birthplace of our species – our foremothers brought with them the original mitochondria. Scientists believe that mitochondrial Eve – the maternal ancestor of all Homo sapiens – lived in Africa about 200,000 years ago. But since then, as generations passed and humans migrated across the planet, each geographic population picked up different mutations in their mitochondrial DNA. For instance, South Americans picked up vastly different mutations than East Asians.

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Unlike nuclear DNA which we inherit from both of our parents, mitochondrial DNA can only be inherited maternally. Nuclear DNA encodes for the majority of our biological traits (such as height, eye and hair colour), where as mitochondrial DNA only directs function related to the mitochondria. Image obtained from BioNinja.

Scientists now call these minor changes in our mitochondrial DNA haplogroups which are unique to each ancient human population and can be used to define our matrilineal ancestry. By identifying which mutations we have in our mitochondrial DNA, we can figure out our haplogroups (ie. where our ancestors came from).

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As humans migrated out of Africa, mutations accumulated in different populations forming the reconstructed haplogroup map we have today, detailing our ancestors journey across the planet. Mitochondrial haplogroups are denoted here as single alphabetical letters with or without a number. Image obtained from world families.net. 

The biotech company, 23andMe, offers an ancestry report for approximately $250 Canadian. The analysis of our mitochondria haplotypes is amongst one of the many tests performed by their ancestry kits. But instead of blowing a couple hundred dollars for some fancy pants scientist to study something that our own bodies make for free, we thought why not embrace that Pinterest patented DIY spirit and do it ourselves!

WARNING – this isn’t something you would be able to do in your own kitchen. But it can be easily done if you know someone who has access to some basic laboratory equipment.

Check out More Than Just a Meme – How We Traced Our Maternal Lineage Using Our Mitochondria (Part 2) where we give you a step by step guide on how to sequence your own mitochondrial DNA and determine your own haplogroups!

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