October 23, 2013
Your DNA Is Haunted
Deoxyribonucleic acid, better known as DNA, is old. We are not referring to Carson Palmer old; we are talking Tyrannosaurus Rex old. This nifty little sequence is simply ancient. Consider how long DNA has been around. Can there be life without it? (Talk about a brainteaser!)
We often get excited about finding the remnants of an ancient city or organism. However, we carry a living genomic record in our own cells. Our DNA represents our eukaryotic lineage. We have only recently begun to understand its intricacies.
If I were to personify DNA, I would say that it is an elderly King who is slightly obsessive compulsive. In my world, King DNA sits on his throne (the nucleolus) and regulates tasks to his subjects (the RNA). These tasks are accomplished in the same manner each and every day. This jovial personification comforts me; it allows me to believe that there is some level of control and order in my cells.
Unfortunately, DNA has a bit more personality than that. Picture your genome as a group of mobsters instead. Your DNA has some tasks that must always be done to sustain the organization, such as the heists and bank robberies (creation of proteins). It also has a few long-term projects, such as government black mail (or cellular replication). Occasionally, unsatisfactory members of the team must be eliminated (chopping of the chromosomes). And finally, there are the rebellious members. They are the ghosts of the organization that wander around, do what they want, and sometimes wreck havoc.
Scientifically known as “transposable elements,” these ghost sequences are able to move from place to place within your genome. They achieve this by cutting themselves out of sequence and pasting themselves elsewhere, or, through RNA intermediary action. Allow me to restate that. Transposable elements arbitrarily decide to rearrange themselves. They haunt your DNA and answer to nobody.
These “ghosts” were first discovered when geneticists studied Indian corn. Indian corn, or Zea mays is characterized by its multicolored kernels. It comes in a variety of colors, such as white, yellow, or purple. These colors can be mixed in many ways. Grains of corn can be solid colored, polka dotted, or mottled in appearance. Scientists were confused for a number of years because the coloring of Indian corn defies Medelian genetics.
When scientists studied this phenomenon, they discovered that there were segments of DNA wandering around within the genome turning different color regions on and off. This caused the unpredictable coloring of the Indian corn. These segments were referred to as transposons. They are rogue sequences, the ghosts of the genome.
Something even scarier: these ghosts make up over 50 percent of our DNA sequence. Although most of this DNA has been deemed inactive, scientists are still trying to understand its existence. We know that the more complex an organism is, the more likely they are to possess transposable elements. Basically, our living record is full of things that we do not understand. The genomic record has been barely scratched.
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