When I was kid I used to watch the Incredible Hulk on TV and wait for Bruce Banner to fly into a rage, his muscles inflating like balloons, pants torn to shreds while his entire body turns green as he transforms into the Hulk. As I grew up, and learned more about the advances in genetics, it never occurred to me that cutting-edge genome-editing techniques could explain the scientific principles behind the Hulk's metamorphosis or his fellow Marvel Comics star-spangled hero Captain America. In a recent Stanford Report story, Sebastian Alvarado, a postdoctoral research fellow in biology, creatively applies the concepts of epigenetics to illuminate the process by which average Joes become superheroes.
As Alvarado notes in the piece and above video, over the past 70 years scientists have developed tools for selectively activating and deactivating individual genes through chemical reactions, a process termed epigenetics. Similar to flipping on a light, switch gene expression can be "turned on" or "turned off. "We have a lot of genome-editing tools - like zinc finger nucleases, or CRISPR/Cas9 systems - that could theoretically allow you to epigenetically seek out and turn on genes that make your muscles physically large, make you strategically minded, incredibly fast, or increase your stamina," he said.
In the case of Captain America, the process of deliberately switching on and off genes could offer a real-world explanation as to how scrawny Steve Rodgers gained extraordinary, strength, stamina and intelligence after being injected with "Super Solider Serum" and then blasted with "Vita-Rays." When it comes to Bruce Banner, a little more creative license is required. Alvarado's theory is:
First, when gamma radiation hits DNA, it breaks the molecule's double-stranded, ladder-like helix, a process known as chromothripsis. Your body can repair a few breaks without significant loss of function.
If many breaks occur - say, if you were caught in a giant gamma explosion - the repairs can become sloppy, and new instructions can be keyed into the genetic code. Alvarado suggested that it's possible that when Banner's DNA reassembled after the initial blast, it now included a handful of epigenetic switches. Instead of the switches being activated by light, however, the hormones produced when Banner is angry might flip the genetic switches to reconfigure his DNA to transform him into the big, green Hulk.
As for the Hulk's skin turning green, anyone who has suffered a nasty bruise has firsthand knowledge of the process that might be behind this transformation. When you bruise, red blood cells at the point of injury die and the oxygen-carrying molecule on their surface, hemoglobin, begins to break up. One of hemoglobin's metabolites, Alvarado said, is a molecule called biliverdin, which can make the blood appear green and is responsible for the avocado hue at the edge of a bruise.
Giant gamma explosion and epigenetics aside, there's one question that has scientifically stumped Alvarado: How do the Hulk's pants stay on after every transformation?
Jen Baxter is a freelance writer and photographer. After spending eight years working for Kaiser Permanente Health plan she took a self-imposed sabbatical to travel around South East Asia and become a blogger. She enjoys writing about nutrition, meditation, and mental health, and finding personal stories that inspire people to take responsibility for their own well-being. Her website and blog can be found at www.jenbaxter.com.
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